JP6010420B2 - Light emitting element and stereoscopic image display device - Google Patents

Description

  The present invention relates to a light emitting element including a structure for specifying a light emitting direction and a stereoscopic image display apparatus using the light emitting element.

  Conventionally, holography, parallax stereogram, lenticular sheet, integral photography (hereinafter referred to as IP) and the like are known as representative methods of image reproduction type stereoscopic display. Regarding the practical application of these methods, excluding holography, it is thought that it can be realized at an early stage with a simple method that does not require coherent light. Moreover, since IP can express parallax information in the vertical direction in addition to the horizontal direction, it is considered promising for early realization of a device capable of natural stereoscopic display (see, for example, Non-Patent Document 1). .

  The IP display system includes a lens array in which a large number of minute lenses (element lenses) that reproduce light rays are arranged, and a display that displays a large number of images (element images) corresponding to each lens. The observer obtains partial information corresponding to the position of the observer from one element image corresponding to one element lens, and observes a stereoscopic image in which element images are arranged by the number of element lenses. In the IP display system, the resolution of the stereoscopic image is determined by the resolution of the element lens, the resolution of the element image, and the viewing distance. Further, regarding the viewing zone angle of the IP display system, the performance of the element lens is a dominant factor. Under such circumstances, in order to generate a practical stereoscopic image by the IP method, it is indispensable to increase the definition and function of the light emitting element and the optical element (for example, see Non-Patent Document 2).

  However, even if the definition of the light emitting element and the optical element is increased, an optical system using a lens has performance limits that cannot be removed in principle, such as the diffraction limit and focal length of the lens. For example, if the pixel size of the display is smaller than the minimum spot size of the element lens, image blurring occurs, so it is necessary to reduce the spot size at the same time, but in principle it is necessary to make the spot size smaller than the Abbe diffraction limit. Impossible.

  The viewing zone angle in a system using a lens is inversely proportional to the focal length of the element lens, but the focal length of the element lens cannot be made infinitely small in order to increase the viewing zone angle. Furthermore, since the viewing zone angle is proportional to the pitch of the element lens, if the pitch of the element lens is increased, the viewing zone angle can be enlarged, but the resolution deteriorates. There is a trade-off relationship between viewing zone angles.

On the other hand, in the field of light-emitting elements, LEDs (Light Emitting Diodes), which are self-light-emitting elements, have attracted attention in various applications since their light-emitting characteristics have advanced dramatically in recent years. LED is a promising device for display applications because it has a high degree of light emission characteristics such as high color purity, as the light diffusivity is so strong that it needs a mechanism for diffusing light in applications such as lighting fixtures. Conceivable.
As an application of the display, for example, in Patent Document 1, a high-definition image in which fine LEDs are two-dimensionally arranged, which are manufactured by separating LEDs formed on a wafer for each pixel and then transferring them to a mounting substrate. A display device is described.

  Various proposals have been made on the electrodes provided on the surface side of the LED because they are related to the aperture ratio of the pixels and need to reliably control each pixel (for example, Patent Document 2 and Patent Document 3). In addition, an attempt to apply a fine structure to a display for the purpose of improving the extraction efficiency of LED radiation is proposed (Patent Document 5).

JP 2002-62825 A JP 2011-146597 A JP 2011-1114075 A JP 2010-171289 A JP 2007-227355 A

“Ultra-high-definition video technology / stereoscopic video technology”, Journal of the Institute of Electronics, Information and Communication Engineers, May 2010, Vol. 93, no. 5, p. 372-381 Association for Promotion of Mechanical Systems and Optoelectronics Technology Promotion Association, “Survey Report on Formation of Spatial Image that Enables Natural Stereoscopic Vision—Summary”, Research Survey on System Technology Development 19-R-5, 2008 March, p. 14-16

  As described above, light wave control using a lens or a surface shape is indispensable for forming a stereoscopic image. However, in addition to the electrodes in contact with the LED mounted on the mounting substrate, electrodes are also formed on the surface side of the LED, which is the side from which light output is obtained. In order to form a simple structure, it is necessary to devise a structure that secures an opening having a sufficient area for processing. In order to achieve finer and higher-density pixels in order to increase the definition of the display, a configuration of a surface-side electrode that has little influence on the opening is desired.

However, in the image display device described in Patent Document 1, it is necessary to arrange pixels composed of LEDs separated into chips on a mounting substrate and to arrange electrodes in the vicinity. Not disclosed. In addition, the LEDs described in Patent Document 2 to Patent Document 5 are all configured to have an electrode on the light emitting surface side, and no proposal of a structure that can provide a sufficient opening on the surface is found.
Accordingly, an object of the present invention is to provide a light-emitting element that includes a structure that specifies the light emission direction and is suitable for miniaturization and high density of pixels, and a stereoscopic image display device including the light-emitting element. .

To solve the problems described above, the light-emitting device according to the present invention includes a first semiconductor layer, a light emitting layer, a second semiconductor layer are laminated in this order, the first electrode connected to said first semiconductor layer And a second electrode connected to the second semiconductor layer, the light emitting element having a light emitting structure, wherein the light emitting layer is formed on a part of the second semiconductor layer or on the upper surface of the second semiconductor layer. An emission direction specifying unit having a structure for specifying the direction of light emitted from the first electrode, the first electrode being directly under the structure and in contact with a part of the lower surface of the first semiconductor layer The carrier mobility of the second semiconductor layer is greater than the carrier mobility of the first semiconductor layer and the carrier that moves in the light emitting layer through the first semiconductor layer; and the second semiconductor layer When the moving carrier recombines and emits light, Recombination time is the time required for the recombination is constructed as shorter than a is the relaxation time time required for replenishment of carriers extinguished by the recombination.

According to such a configuration, when a voltage is applied between the first electrode and the second electrode, the light emitting element uses the first semiconductor layer as the transport layer from the first electrode as a carrier (for example, the first semiconductor layer is a p-type semiconductor). In the case of a layer, carriers are holes), and carriers (for example, if the second semiconductor layer is an n-type semiconductor layer are carriers) move from the second electrode using the second semiconductor layer as a transport layer. Carriers that have moved through the semiconductor layer are recombined in the light emitting layer to emit light and disappear. At this time, in order to replenish the carriers annihilated in the light emitting layer, the carriers moving through the first semiconductor layer are recombined later than the carriers moving through the second semiconductor layer and the relaxation time during which the carriers are replenished. The time is shorter. For this reason, in the light-emitting layer, carrier recombination occurs in a region immediately above the first electrode, which is a region where carriers (holes) are replenished most rapidly from the first electrode through the first semiconductor layer. Frequency is high and selectively emits light.
The light emitted from the region immediately above the first electrode of the light emitting layer is incident on a structure provided directly above the first electrode, and the light is emitted in a predetermined direction specified by the structure. .

The light emitting device of claim 1, prior Symbol structures, N present for emitting light from the stigmas of the exit surface (N is an integer of 3 or more) has a columnar portion of the columnar portion of the N book, The light emitted from the light emitting layer is arranged in a ring shape within a range where interference is possible, and the height of at least one of the N columns is different from the height of the other columns, The difference in the height of the columns was set to be half or less of the wavelength of the light emitted from the light emitting layer inside the columnar portion.

  According to this configuration, light from the light emitting layer is incident on the structure and is emitted from the stigma which is the emission surface of the plurality of columnar portions. Since the light emitted from these emission surfaces has low coherence based on the properties of the light emitting element, the light emitted from the plurality of columnar portions is not separated too much, the interference occurs with each other. Combined to form a light beam. Further, the light emitting element is configured such that the height of at least one of the plurality of columnar portions is different from the height of the other columnar portions, thereby providing a phase difference in the light emitted from each emission surface, A light beam is emitted in a direction corresponding to the phase difference. That is, the light emitting element emits a light beam in a specific direction corresponding to a preset height difference of the columnar part.

The light emitting device according to claim 2 is configured such that, in a plan view, the area of the first electrode is equal to or less than the area of a circumscribed circle surrounding the N columnar portions in the light emitting device according to claim 1. did.
According to this configuration, the light emitting element suppresses light emitted from the light emitting layer in the region immediately above the first electrode from leaking from the surface of the light emitting element other than the emission surface of each columnar part. This suppresses excessive interference between the light leaking from the surface of the light emitting element and the light emitted from the emission surface of each columnar part.

The light emitting device according to claim 3 is the light emitting device according to claim 1 or 2 , wherein the area of the first electrode is not less than the sum of the areas of the N columnar portions in plan view. Configured.
According to this configuration, most of the light emitted from the light emitting layer immediately above the first electrode is incident on each columnar part. Thereby, the intensity of light emitted from the emission surface of each columnar portion is increased.

The light emitting device according to claim 4, before Symbol structure has a columnar recess of the N recessed from the upper surface of the columnar (N is an integer of 3 or more), the columnar recess of the N present, the light-emitting layer Is provided in a ring shape within a coherent range, and the depth of at least one of the N columnar recesses is different from the depth of the other columnar recesses, and the depth of the columnar recesses The difference is configured to be not more than half of the wavelength of the light emitted from the light emitting layer inside the columnar recess.

  According to such a configuration, light from the light emitting layer enters the structure and is emitted from the bottom surface, which is the emission surface of the plurality of columnar recesses. Since the light emitted from these emission surfaces has low coherence based on the properties of the light emitting element, the light emitted from the plurality of columnar portions is not separated too much, the interference occurs with each other. Combined to form a light beam. Further, the light emitting element is configured such that the depth of at least one of the plurality of columnar recesses is different from the depth of the other columnar recesses, thereby providing a phase difference in the light emitted from each emission surface, A light beam is emitted in a direction corresponding to the phase difference. That is, the light emitting element emits a light beam in a specific direction corresponding to a preset difference in the depth of the columnar recess.

The light emitting device according to claim 5 is configured such that, in plan view, the area of the first electrode is equal to or less than the area of a circumscribed circle surrounding the N columnar recesses in the light emitting device according to claim 4. did.
According to this configuration, the light emitting element suppresses light emitted from the light emitting layer in the region immediately above the first electrode from leaking from the surface of the light emitting element other than the emission surface of each columnar recess. This suppresses excessive interference between the light leaking from the surface of the light emitting element and the light emitted from the exit surface of each columnar recess.

The light emitting device according to claim 6 is the light emitting device according to claim 4 or 5 , wherein the area of the first electrode is not less than the sum of the areas of the N columnar recesses in plan view. Configured.
According to this configuration, most of the light emitted from the light emitting layer in the region immediately above the first electrode is incident on each columnar recess. This increases the intensity of light emitted from the exit surface of each columnar recess.

The light emitting device according to claim 7, in the light emitting device according to any one of claims 1 to 6, the refractive index of the emission direction identification unit is smaller than the refractive index of the second semiconductor layer It was configured as follows.
According to such a configuration, the light emitting element specifies the emission direction of the light beam according to the phase difference generated when guiding each columnar portion or each columnar recess having a small refractive index.

The stereoscopic image display device according to claim 8 is the stereoscopic image display device of the integral photography method, on a substrate, a display panel provided by arranging a two-dimensional array of light emission elements as pixels Pixel selection means for selecting at least one of the pixels, and the light emitting element includes a first semiconductor layer, a light emitting layer, and a second semiconductor layer stacked in this order, A light emitting structure having a first electrode to be connected and a second electrode to be connected to the second semiconductor layer, wherein the light emission is formed on a part of the second semiconductor layer or on an upper surface of the second semiconductor layer. An emission direction specifying portion having a structure for specifying the direction of light emitted from the layer, wherein the first electrode is directly under the structure and is in contact with a part of the lower surface of the first semiconductor layer Carrier movement of the second semiconductor layer Is larger than the carrier mobility of the first semiconductor layer, and the carrier moving through the first semiconductor layer and the carrier moving through the second semiconductor layer in the light emitting layer recombine and emit light. The recombination time, which is the time required for the recombination, is shorter than the relaxation time, which is the time required for the replenishment of the carriers annihilated by the recombination, and the pixel is selected by the pixel selection means, and the selected pixel emits light. And non-luminous control.

  According to such a configuration, the stereoscopic image display device selects light emitting elements arranged in a two-dimensional array as pixels by the pixel selecting unit, controls light emission and non-light emission, and integrates the display panel with the integration. 3D image of Le Photography system is displayed. At this time, for example, the emission direction of the light beam from each pixel is specified using the interference of light by the emission direction specifying unit configured by a plurality of columnar portions and a plurality of columnar recesses.

According to the present invention, since the region directly above the first electrode of the light emitting layer can be selectively made to emit light, the light emitting layer necessary for the configuration of the emission direction specifying portion is required only by determining the shape of the first electrode. The area can be illuminated. Further, since the configuration of the emission direction specifying portion is not affected by the arrangement of the second electrode, the light emitting element can be miniaturized and densified .

According to the invention described in claim 1 or claim 4 , it is possible to specify the light emitting direction by utilizing interference of light with a structure having a simple configuration in which a plurality of columnar portions or a plurality of columnar concave portions are provided. Therefore, miniaturization and high density of the light emitting element can be facilitated.
According to invention of Claim 2 or Claim 5 , the excess interference with the light which leaked from the surface of the light emitting element, and the light radiate | emitted from the output surface of each columnar part or each columnar recessed part is suppressed. Therefore, the arbitraryness of the direction of the light emitted from the light emitting element can be improved.
According to the invention described in claim 3 or claim 6 , since the intensity of light emitted from the emission surface of each columnar part or each columnar recess can be increased, the clarity of the light emitted from the light emitting element. Can be improved.
According to the seventh aspect of the invention, it is desirable to specify the emission direction of the light beam according to the phase difference generated when guiding each columnar part or each columnar concave part made of a material having a small refractive index. Therefore, the accuracy of the difference in the height of the columnar portions or the difference in the depth of the columnar recesses required to cause the phase difference can be reduced.
According to the invention described in claim 8 , since the direction of the light beam from each pixel is specified by the emission direction specifying unit using the interference of light, the definition is higher than that of a stereoscopic image display device using a lens. can do.

It is a typical perspective view which shows the structure of the light emitting element which concerns on 1st Embodiment of this invention. It is a schematic diagram which shows the structure of the light emitting element which concerns on 1st Embodiment of this invention, (a) is a schematic plan view, (b) shows typical sectional drawing in the AA of (a). It is explanatory drawing for demonstrating the operation | movement on one condition of the light emission structure part in this invention. It is explanatory drawing for demonstrating operation | movement of the light emission structure part in this invention, (a), (b) shows the mode of carrier concentration distribution and a recombination, (c) is typical sectional drawing of a light emission structure part. Show. It is explanatory drawing for demonstrating the operation | movement on the other conditions of the light emission structure part in this invention. It is typical sectional drawing for demonstrating the area | region where light is radiated | emitted outside from the light emission structure part in this invention. It is a typical top view for demonstrating arrangement | positioning of the columnar part of the light emitting element which concerns on 1st Embodiment of this invention. It is a typical top view for demonstrating the relationship between arrangement | positioning of the columnar part of the light emitting element which concerns on 1st Embodiment of this invention, and a light emission area | region. It is typical sectional drawing for demonstrating the principle which pinpoints the output direction by the light emitting element which concerns on 1st Embodiment of this invention. It is a schematic diagram for demonstrating a part of process in the manufacturing method of the light emitting element which concerns on 1st Embodiment of this invention, (a) is a schematic plan view, (b) is the AA line of (a). It is a typical sectional view in. It is a schematic diagram for demonstrating a part of process in the manufacturing method of the light emitting element which concerns on 1st Embodiment of this invention, (a)-(c) is typical sectional drawing in each process. It is a schematic diagram for demonstrating a part of process in the manufacturing method of the light emitting element which concerns on 1st Embodiment of this invention, (a)-(c) is typical sectional drawing in each process. It is a schematic diagram for demonstrating a part of process in the manufacturing method of the light emitting element which concerns on 1st Embodiment of this invention, (b) is a schematic plan view, (a) is the AA line of (b). It is a typical sectional view in. It is a schematic diagram which shows the structure of the light emitting element which concerns on the modification of 1st Embodiment of this invention, (a) is typical top view, (b) is typical sectional drawing in the AA of (a). Show. It is a typical perspective view which shows the structure of the light emitting element which concerns on 2nd Embodiment of this invention. It is a schematic diagram which shows the structure of the light emitting element which concerns on 2nd Embodiment of this invention, (a) is a schematic plan view, (b) shows typical sectional drawing in the AA of (a). It is a schematic diagram which shows the structure of the light emitting element which concerns on the modification of 2nd Embodiment of this invention, (a) is typical top view, (b) is typical sectional drawing in the AA of (a). Show. It is a conceptual diagram of the IP stereoscopic display which concerns on 3rd Embodiment of this invention, (a) is a front view, (b) is a perspective view. It is a block diagram which shows the structure of the IP stereoscopic display which concerns on 3rd Embodiment of this invention.

  Hereinafter, embodiments for carrying out the light-emitting element of the present invention will be described in detail with reference to the drawings. Note that the size and positional relationship of members and the like shown in the drawings may be exaggerated for clarity of explanation.

<First Embodiment>
[Outline of light emitting device structure]
First, the structure of the light emitting device 1 according to the first embodiment will be described with reference to FIGS. 1 and 2. The light-emitting element 1 according to the present embodiment is an element that emits light having high directivity, and is a light-directional light-emitting element that emits light in a specific direction.
As shown in FIGS. 1 and 2, the light emitting device 1 according to this embodiment includes a light emitting structure 2 that emits light and an emission direction specifying unit 3 that emits light emitted from the light emitting structure 2 in a specific direction. And are laminated.

  In the light emitting structure 2, a p-type semiconductor layer (first semiconductor layer) 21, a light emitting layer 22, and an n-type semiconductor layer (second semiconductor layer) 23 are stacked in this order. A p-side electrode (first electrode) 24 that is electrically connected and an n-side electrode (second electrode) 25 that is electrically connected to the n-type semiconductor layer 23 are provided. The light emitting structure 2 applies a voltage pulse of a predetermined level between the p-side electrode 24 that is an anode and the n-side electrode 25 that is a cathode, so that holes are injected into the p-type semiconductor layer 21 and the n-type electrode. The LED element emits light when electrons are injected into the semiconductor layer 23 and holes and electrons are recombined in the light emitting layer 22. The p-side electrode 24 is provided so as to be in contact with a central portion that is a part on the lower surface side of the p-type semiconductor layer 21, and is provided so that the contact surface with the p-type semiconductor layer 21 has a circular shape. The n-side electrode 25 is provided so as to be in contact with part of the side surface of the n-type semiconductor layer 23.

In the present embodiment, the mobility of electrons that are carriers (carrier mobility) in the n-type semiconductor layer 23 is larger than the mobility of carriers that are carriers in the p-type semiconductor layer 21 (carrier mobility). The light-emitting layer 22 is configured using a semiconductor material in which the carrier recombination time is shorter than the carrier diffusion time. For this reason, in the light emitting layer 22, carrier recombination frequently occurs in the light emitting region 22 a that is directly above the contact surface between the p-side electrode 24 and the p-type semiconductor layer 21 and has substantially the same planar shape as the contact surface. Emits light.
Note that details of the relationship between the carrier mobility, the recombination time, and the light emitting region will be described later.

The p-type semiconductor layer (first semiconductor layer) 21 is a transport layer that transports holes that are carriers injected from the p-side electrode 24, and is a p-side electrode that contacts the center of the lower surface in a circular shape in plan view 24 is provided.
The n-type semiconductor layer (second semiconductor layer) 23 is a transport layer that transports electrons that are carriers injected from the n-side electrode 25, and is provided with the n-side electrode 25 in contact with part of the side surface. In addition, an emission direction specifying unit 3 is provided on the upper surface of the n-type semiconductor layer 23, and guides light emitted from the light emitting region 22 a of the light emitting layer 22 to the emission direction specifying unit 3. The semiconductor material is selected such that the carrier mobility in the n-type semiconductor layer 23 is larger than the carrier mobility in the p-type semiconductor layer 21.
Each of the p-type semiconductor layer 21 and the n-type semiconductor layer 23 can have a single layer structure, but can also have a multilayer structure.

  The light emitting layer 22 is provided at the interface between the p-type semiconductor layer 21 and the n-type semiconductor layer 23, and is transported through the n-type semiconductor layer 23 and holes that are carriers transported through the p-type semiconductor layer 21. This layer emits light by recombination with electrons as carriers. The light emitting layer 22 is formed in the region immediately above the contact surface between the p-side electrode 24 and the p-type semiconductor layer 21 and in the vicinity thereof, depending on the relationship between the carrier mobility and the recombination time in the p-type semiconductor layer 21 and the n-type semiconductor layer 23. A certain light emitting area 22a emits light, and other areas do not emit light.

As the semiconductor layer composed of the p-type semiconductor layer 21, the light emitting layer 22, and the n-type semiconductor layer 23, a compound semiconductor such as GaN or GaAs, a silicon semiconductor, or the like can be used. Further, in order to make the light emitting region 22a coincide with the region directly above the contact surface between the p-side electrode 24 and the p-type semiconductor layer 21, it is preferable that the difference in carrier movement between the p-type semiconductor layer 21 and the n-type semiconductor layer 23 is larger. The carrier recombination time is preferably sufficiently shorter than the carrier diffusion time determined by the carrier mobility. As such a semiconductor material, a GaN-based compound semiconductor can be preferably used.
Further, the light emitting layer 22 may form a quantum well layer having a multilayer structure.

  In the present embodiment, the light emitting structure 2 is configured such that the p-type semiconductor layer 21 is a lower layer. However, the p-type semiconductor layer 21 having a carrier mobility larger than the carrier mobility in the n-type semiconductor layer 23. When n is used, the n-type semiconductor layer 23 can be configured as a lower layer.

  The light emitting region 22 a is a region located immediately above and in the vicinity of the contact surface of the light emitting layer 22 between the p-side electrode 24 and the p-type semiconductor layer 21. As described above, the light emitting region 22 a is a region that selectively emits light in the light emitting layer 22 due to the relationship between carrier mobility and recombination time in the p-type semiconductor layer 21 and the n-type semiconductor layer 23.

The p-side electrode (first electrode) 24 is a positive electrode provided directly below the structure 3 a and on the lower surface of the p-type semiconductor layer 21 to inject carriers into the p-type semiconductor layer 21. The p-side electrode 24 has a cylindrical shape, and is provided so that the circular upper surface is in contact with a part of the lower surface of the p-type semiconductor layer 21. The p-side electrode 24 is made of a conductive compound such as metal or ITO (indium tin oxide). The p-side electrode 24 may have a multilayer structure in which a plurality of types of conductive materials are stacked.
Note that the shape of the p-side electrode 24 is not limited to a cylindrical shape, and may be an arbitrary shape such as a prismatic shape, a needle shape, a spherical shape, or a hemispherical shape. In addition, the shape of the contact surface with the p-type semiconductor layer 21 is not limited to a circular shape, and may be an ellipse or a polygon. The shape and size of the contact surface depends on the structure of the structure 3a. Can be determined.
Further, the p-side electrode 24 is surrounded by an insulating material for supporting the p-type semiconductor layer 21 except for a contact surface with the p-type semiconductor layer 21 and a connection portion with a wiring for inputting a power source or a signal. It may be.

  The n-side electrode (second electrode) 25 is a negative electrode that is provided on a part of the side surface of the n-type semiconductor layer 23 and injects carriers into the n-type semiconductor layer 23. The n-side electrode 25 may be provided so as to be in contact with a part of the n-type semiconductor layer 23, and is not limited to a part of the side surface. The n-side electrode 25 may be provided so as to surround the upper part of the side surface, or the structure 3a may be provided in plan view. You may provide in the outer edge part of the upper surface except the provided area | region. In any case, it is preferable to provide the structure 3a on the upper surface of the n-type semiconductor layer 23 so as not to become an obstacle. The n-side electrode 25 can be configured using a metal or a conductive compound, similarly to the above-described p-side electrode.

The emission direction specifying unit 3 is provided on the upper surface side of the light emitting structure unit 2, and changes the direction of the light emitted from the light emitting element 1 by using the light interference action of the light emitted from the light emitting layer 22 of the light emitting structure unit 2. It has the structure 3a to identify. In the present embodiment, the emission direction specifying part 3 has a structure 3 a on the upper surface 30 a of the bottom part 30.
The upper surface 30a of the bottom portion 30 is a flat surface other than the region where the structure 3a is provided, has three or more columns (columnar portions) so as to surround the predetermined region, and the bottom portion 30 of at least one columnar portion. Unlike the heights of the other columnar portions, the height from the upper surface 30a (hereinafter simply referred to as the “columnar portion height”) emits light from the upper surfaces of all these columnar portions. And it makes it have intensity | strength in a specific direction using the interference of the lights radiate | emitted from the upper surface of these columnar parts.

  The structure 3a specifies the direction of the light emitted from the light emitting element 1 by using the light interference action of the light emitted from the light emitting layer 22 of the light emitting structure section 2. In the present embodiment, the structure 3a is composed of three columnar portions 31, 32, 33 having a circular cross section. In the present embodiment, the columnar portion 33 is described as being lower than the columnar portions 31 and 32.

The bottom portion 30 is a portion that becomes a base of the emission direction specifying portion 3, and is in contact with the upper surface of the light emitting structure portion 2. The upper surface 30a of the bottom 30 is a flat surface except for the region where the structure 3a is provided, and three columnar parts 31, 32, 33 are provided as the structure 3a.
The columnar portions 31, 32, and 33 are light guide members that propagate light incident from the light emitting structure portion 2 through the bottom portion 30 and emit the light from the upper surfaces 31 a, 32 a, and 33 a. The columnar portions 31, 32, 33 are formed on the upper surface of the bottom portion 30 such that the height of the columnar portion 33 from the upper surface of the bottom portion 30 is lower than the height of the columnar portions 31, 32 from the upper surface of the bottom portion 30. Yes. The light emitted from the upper surfaces 31a, 32a, 33a of the columnar portions 31, 32, 33 interferes with each other, and the direction according to the arrangement of the columnar portions 31, 32, 33 (the direction in the plane parallel to the upper surface 30a of the bottom portion 30). , And an elevation angle with respect to the plane) is emitted from the emission direction specifying unit 3.
The details of the principle of specifying the light emission direction by the emission direction specifying unit 3 will be described later.

The emission direction specifying unit 3 can be made of a material having translucency with respect to incident light. For example, a dielectric material such as SiO ₂ or Al ₂ O ₃ can be used. Further, the semiconductor material similar to that of the n-type semiconductor layer 23 can be used.
Moreover, although the output direction specifying part 3 in the present embodiment is configured to provide the columnar parts 31, 32, 33 via the bottom part 30, the present invention is not limited to this. For example, the columnar portions 31, 32, and 33 that are the structures 3 a may be provided directly on the upper surface of the light emitting structure portion 2 without providing the bottom portion 30. Further, instead of providing the emission direction specifying portion 3 on the upper surface of the light emitting structure portion 2, a part of the n-type semiconductor layer 23 (for example, the n-type buffer layer) that is the upper portion of the light emitting structure portion 2 is processed to form a column The portions 31, 32, and 33 may be formed.
Moreover, the columnar parts 31, 32, and 33 are not limited to a cylindrical shape, and may be polygonal columns. Moreover, the number of columnar parts should just be three or more, for example, can also be set to six.

[Relationship between carrier mobility, recombination time and emission region]
Next, the relationship among the carrier mobility, the carrier recombination time, and the light emitting region 22a in the p-type semiconductor layer 21 and the n-type semiconductor layer 23 will be described with reference to FIGS. Here, it is assumed that the carriers in the p-type semiconductor layer 21 are holes, the carriers in the n-type semiconductor layer 23 are electrons, and the electron mobility is higher than the hole mobility.
As shown on the left side of FIG. 3, when a voltage is applied between the p-side electrode 24 and the n-side electrode 25, an electric field is formed in the light emitting structure 2 as schematically indicated by the lines of electric force (broken lines). Is done.
Holes that are carriers in the p-type semiconductor layer 21 and electrons that are carriers in the n-type semiconductor layer 23 move so as to cancel this electric field. As a result, a carrier concentration distribution is formed as schematically shown on the right side of FIG.
Note that the carrier concentration distribution shown on the right side of FIG. 3 shows a state in which the cross section along the two-dot chain line in the light emitting structure 2 shown on the left side is observed obliquely from above, and is shown darkly. The region shows that the carrier concentration is higher.
3 shows an enlarged view of the vicinity of the light-emitting layer 22 that is a junction between the p-type semiconductor layer 21 and the n-type semiconductor layer 23. The aspect and the like of the light emission shown in FIG. 1 and FIG. It does not correspond exactly to the structure part 2. The same applies to FIGS. 4 and 5 to be described later.

The electrons and holes distributed like the carrier concentration distribution shown in FIG. 3 recombine based on a certain probability, and emit light and disappear. For this reason, the electric field (that is, charge distribution) fluctuates with recombination. The electrons and holes move so as to eliminate the concentration gradient in the region where the charge is lost. At this time, the time required for recombination (hereinafter referred to as recombination time) is sufficiently faster (short) than the time required for movement of electrons and holes to eliminate the concentration gradient (hereinafter referred to as relaxation time). In this case, the electric field does not return to the steady state shown in FIG. This is because, when the recombination time is shorter than the relaxation time in the p-type semiconductor layer 21 and the n-type semiconductor layer 23 which are carrier transport layers, when the conditions for pairing electrons and holes are met. This is because they immediately recombine and disappear.
Whether or not the recombination time is sufficiently shorter than the relaxation time will be described later in the description of the evaluation using the diffusion time, which is the time required for carriers to spread in a region of the same size as the electrode size.

With reference to FIG. 4, the light emitting region 22a in the case where the carrier mobility in the n-type semiconductor layer 23 is larger than the carrier mobility in the p-type semiconductor layer 21 and the recombination time is sufficiently smaller than the relaxation time will be described. .
In an initial state assuming that no recombination occurs, the carrier concentration distribution is a distribution that depends on the electric field distribution, as shown in FIG. At this time, the frequency at which recombination occurs in the light emitting layer 22 corresponds to the correspondence between the point P1 in the region L where the gradient of the electric field is large, that is, the region where the hole concentration is high in the p-type semiconductor layer 21, It becomes higher between the point Q1 or the point Q2 in the high electron concentration region in the n-type semiconductor layer 23 and the corresponding point P2 in the p-type semiconductor layer 21.

  When recombination occurs and carriers disappear, the carrier concentration in the vicinity of the light emitting layer 22 in the p-type semiconductor layer 21 and the n-type semiconductor layer 23 temporarily decreases. Here, electrons that are carriers with high mobility (fast movement) should relax the concentration gradient until holes that are carriers with low mobility (slow movement) reach the light emitting layer 22. It is unevenly distributed in the corresponding semiconductor layer. That is, as shown in FIG. 4B, electrons are quickly replenished not only at the point Q2 in the high concentration region of electrons but also at the point Q1 in the low concentration region of electrons.

On the other hand, holes having a low carrier mobility are replenished relatively quickly with respect to the point P1 in the high-concentration region, as shown in FIG. It takes time to replenish the point P2. Therefore, when the occurrence of recombination continues, the carrier (hole) is insufficient in the low concentration region of holes. For this reason, the frequency with which recombination occurs is high in the high concentration region L1 of holes and low in the low concentration region L2 of holes.
Therefore, as shown in FIG. 4C, recombination selectively occurs in the light emitting region 22a immediately above the p-side electrode 24 of the light emitting layer 22 where the high hole concentration is maintained due to the high electric field strength. To do.
This tendency becomes more prominent as the difference in carrier mobility between the p-type semiconductor layer 21 and the n-type semiconductor layer 23 becomes larger. If the difference is made sufficiently large, the p-side becomes independent of the arrangement of the n-side electrode 25. Localized light emission corresponding to the shape and size of the electrode 24 can be obtained. That is, the region immediately above the p-side electrode 24 of the light emitting layer 22 can be a light emitting region 22a that emits light locally.

Next, referring to FIG. 5, when the recombination time is not sufficiently shorter than the relaxation time, or the difference in carrier mobility between the p-type semiconductor layer 21 and the n-type semiconductor layer 23 is not sufficiently large. The light emitting region 22a in this case will be described.
The phenomenon that occurs when the recombination time is long and the phenomenon that occurs when the difference in carrier mobility is small are apparently the same, and as shown in the diagram on the right side, carriers (holes) in the p-type semiconductor layer 21 are present. ) And a region L extending in a region connecting the high concentration region of the n-type semiconductor layer 23 and the carrier (electron) high concentration region. That is, in the light emitting structure 2, as shown in the left diagram, a region near the n-side electrode 25 is a light-emitting region 22 a with respect to a region immediately above the p-side electrode 24.

When the recombination time is long, the carrier concentration can always take a distribution as shown in FIG. For this reason, both high density regions equally affect the expansion of the light emitting region.
On the other hand, when the difference in carrier mobility is small, the electric field distribution is close to the distribution shown in FIG. For this reason, the movement of the carrier is along the electric lines of force, and the light emission is obtained by spreading in the dense part of the electric lines of force.

Under these conditions, the light emitting region 22a depends on the strength of the electric field formed by the voltage applied to the electrode, so that the effect of localizing the light emission is reduced. That is, under these conditions, the location of the light emitting region 22a depends on the arrangement of both the p-side electrode 24 and the n-side electrode 25.
Therefore, in such a case, the n-side electrode 25 is disposed so as to uniformly cover the surface of the n-type semiconductor layer 23, or the n-side electrode 25 is at least of the p-side electrode 24 on the surface of the n-type semiconductor layer 23. The carrier concentration distribution in the n-type semiconductor layer 23 can be made uniform or substantially uniform by arranging so as to cover the region other than the region above the p-side electrode 24 so as to surround the upper region. As a result, local light emission according to the shape and arrangement of the p-side electrode 24 can be obtained. In particular, the n-side electrode 25 is preferably arranged so as to be symmetric with respect to the central axis of the region where the p-side electrode 24 is arranged. As a result, the concentration distribution of electrons in the n-type semiconductor layer 23 is targeted with respect to the central axis of the region where the p-side electrode 24 is disposed, so that the center of the region where the light-emitting region 22a and the p-side electrode 24 are disposed The axis matches. That is, the region directly above the region where the p-side electrode is disposed can be the light emitting region 22a.

[Specific example of flash area setting]
Next, the configuration of this embodiment and its effects will be described using specific numerical values with reference to FIGS. 1 and 2 as appropriate.
Here, a case where p-type and n-type GaN-based compound semiconductors are used as the p-type semiconductor layer 21 and the n-type semiconductor layer 23 in the light-emitting element 1 will be described.

First, the carrier diffusion time, which is the relaxation time, is estimated using the general solution of the diffusion equation.
Here, the diffusion equation will be briefly described.
When the particle density is n and the diffusion coefficient is D, the diffusion equation is expressed as shown in Equation (1).
∂n / ∂t = D∇ ^{2 n} ... formula (1)
Here, t indicates time.
The solution of this diffusion equation is as shown in Equation (2), where time t = 0 and particle density at position r is n = Nδ (r).
n (r, t) = N / (4πDt) ^3/2 exp [−r ² / 2Dt] (2)

At this time, the time derivative of the variance <r ² > at the position r is expressed as in Expression (3).
d <r ² > / dt = 1 / N · ∫∫∫r ² n (r) dV = 6D Equation (3)
Here, ∫∫∫dV represents the integral over the entire region of the three-dimensional space in which the particle n can exist.
From equation (3), in the diffusion process:
<r ² > = 6 Dt (4)
It becomes.

Further, the diffusion coefficient and the carrier mobility have a relation of Einstein's relational expression shown in Expression (5).
D = (kT / q) · μ Equation (5)
Here, k is a Boltzmann constant, T is an absolute temperature, and μ is the mobility of particles as carriers.

Here, the mobility of carriers (electrons) in the n-type semiconductor of GaN is 1200 [cm ² / Vs], and the mobility of carriers (holes) in the p-type semiconductor is 10 [cm ² / Vs] or less. (See Reference 1).
From equation (5), when 1200 [cm ² / Vs] is substituted as the electron mobility in the GaN-based semiconductor at room temperature (T = 300 [K]), the electron diffusion coefficient De is 3.1 × 10 ^{− 3} [m ² / s]. Further, when 10 [cm ² / Vs] is substituted as the hole mobility in the GaN-based semiconductor, the hole diffusion coefficient Dh is 2.6 × 10 ⁻⁵ [m ² / s].
(Reference 1): “GaN Power Device”, Masahiro Hikida et al., Panasonic Technical Journal, Vol.55, No.2 (2009)

  Accordingly, assuming that the electrode diameter is 100 [μm], the time required for carriers to diffuse in the range of 10 [μm], which is 10% of the electrode diameter, is estimated by the equation (4) using the diffusion coefficient described above. be able to. The electron diffusion time which is the carrier diffusion time in the n-type semiconductor layer 23 is about 5 [ns], and the hole diffusion time which is the carrier diffusion time in the p-type semiconductor layer 21 is about 600 [ns]. Become. That is, this corresponds to a case where there is a significant difference in the carrier diffusion time.

On the other hand, since the recombination lifetime in a GaN-based semiconductor is about 100 to 300 [ps] at 300 [K] (see, for example, Reference 2), the recombination time is sufficiently longer than any carrier diffusion time. This corresponds to a short case. As described above, since the carrier mobility in the p-type semiconductor layer (first transport layer) 21 and the n-type semiconductor layer (second transport layer) 23 has a difference of two digits or more, the size of the p-side electrode 24 is reduced. However, the n-side electrode 25 may have any shape as long as it corresponds to the desired size of the light emitting region 22a, and may be disposed so as to be in contact with any location of the n-type semiconductor layer 23.
(Reference 2): SF Chichibu et al., Appl. Phys. Lett. 86, 021914 (2005)

As another semiconductor having a large difference in carrier mobility between the p-type semiconductor and the n-type semiconductor, for example, a Si-based semiconductor (electron mobility = 1500 [cm ² / Vs], hole mobility = 600 [cm ^2]. / Vs]), GaAs-based semiconductors (electron mobility = 8500 [cm ² / Vs], hole mobility = 400 [cm ² / Vs]) (see Reference 1).

  Next, how to obtain the maximum allowable diameter of the p-side electrode 24 when the diameter of the desired light emitting region 22a (pixel size depending on the application) is 100 μm will be described with reference to FIG. Although the shape of the light emitting region 22a and the shape of the p-side electrode 24 in plan view are described as circles, other shapes such as squares and ellipses can be obtained in the same manner.

As shown in FIG. 6, let the diameter of the p-side electrode 24 in a plan view be Le, the diameter of the light emitting region 22 a be Lp, and the diameter of outgoing light emitted from the upper surface of the light emitting structure 2 be Ls.
As described above, when GaN is used as a semiconductor, the diameter Le of the p-side electrode 24 and the diameter Lp of the light emitting region 22a are substantially the same (Lp) due to the relationship between carrier mobility and recombination time. ≒ Le). The light emitted from the light emitting region 22a spreads when propagating through the n-type semiconductor layer 23, but when emitted from the n-type semiconductor layer 23 to the outside, the refractive index (dielectric constant) of the n-type semiconductor layer 23 is generated. ) And the critical angle θc determined by the external refractive index, the diameter of the light extracted outside is also limited. That is, light incident on the interface between the n-type semiconductor layer 23 and the outside at an incident angle larger than the critical angle θc is totally reflected at the interface and is not extracted outside. Let w be the spread from the region immediately above the light emitting region 22a when the critical angle θc is reached. The thickness of the n-type semiconductor layer 23 is d.
At this time, there is a relationship of Equation (6) between these parameters.
Ls = Lp + 2w
= Lp + 2d · tan θc (6)

  Here, for example, when d = 5 μm and θc = 19 °, the diameter Ls of the light extracted to the outside is Le + 3.4 μm. Therefore, the diameter of the p-side electrode 24 is required to be 93 μm in order to set the diameter Ls of the light extracted outside to 100 μm.

  Next, with reference to FIG.7 and FIG.8, the shape and arrangement | positioning of the three columnar parts 31,32,33 and the light emission area | region 22a which comprise the structure 3a of the output direction specific | specification part 3 are demonstrated.

(Space between columnar parts)
The columnar portions 31, 32, and 33 have a diameter that is approximately equal to or greater than the wavelength λ _{0 of} light emitted from the light emitting region 22 a of the light emitting element 1. Here, the wavelength λ ₀ indicates the wavelength of the emitted light in free space. 7 and 8, the shapes of the columnar portions 31, 32, and 33 in plan view are shown as circles. The thickness of each columnar part 31, 32, 33 was made equal (radius is set to φ). As shown in FIG. 7, the columnar portions 31, 32, and 33 are oriented at a uniform angle α (α = 120 degrees in this example) around a predetermined origin M on the light emission surface of the light emitting element 1. Are spaced apart from each other by a distance p. Further, the interval p between the columnar portions 31, 32, 33 is set to such an extent that light emitted from the adjacent columnar portions 31, 32, 33 can interfere. That is, it is preferable that the columnar portions 31, 32, and 33 have a coherence length of the emitted light or less. The coherence length of light depends on the center wavelength and the half width of the emission spectrum of light emitted from the light emitting structure 2 (see FIG. 1) that is a light source. When the light source is an LED, for example, the length is about 10 to several tens of μm in a vacuum.

(The origin M of the arrangement of the plurality of columnar portions)
In the example shown in FIG. 7, the predetermined origin M is a point located at the center of a predetermined region that is annularly surrounded by the three columnar portions 31, 32, 33 on the upper surface of the element. Further, the origin is the center O ₃ of the columnar portion 33 and the center O ₂ of the columnar portion 32, is a point from the center O ₁ Metropolitan columnar portion 31 at equal distances, the center O _1, O _2, O ₃ Is the center of gravity of an equilateral triangle with the apex at. Here, it is preferable that the three columnar parts 31, 32, and 33 are arranged in an annular shape and equally. The shape and size of the predetermined region surrounded by the columnar parts 31, 32, 33 can be appropriately designed as desired while balancing the diameter of the columnar parts 31, 32, 33. For example the diameter of the columnar portion 31, 32 and 33, if the number wavelengths about partial emission wavelength lambda _0, the size of the predetermined area may be a fraction of the wavelength to several order of the wavelength.

The distance ρ from the origin M to the columnar portions 31, 32, 33 on the lines connecting the origin M and the centers O ₁ , O ₂ , O _{3 of the} columnar portions 31, 32, 33, respectively, is in free space. It is preferable that the wavelength of the emitted light is λ ₀ or less, for example, about ¼ to 1 wavelength. In particular, when the distance ρ is set to be about ¼ of the diameter 2φ of the columnar portions 31, 32, 33, the upper surfaces 31a, 32a, 33a (see FIG. 9) that are the emission surfaces of the columnar portions 31, 32, 33. It is preferable because the light emitted from each other can interfere with each other and can be molded well and a sufficiently strong light beam can be emitted.

As shown in FIG. 9, among the columnar portions 31, 32, 33, the heights of the two columnar portions 31, 32 from the upper surface 30a of the bottom 30 that is a reference surface are respectively set as a reference height H and To do. If the difference between the height of the columnar portion 33 and the height of the other columnar portions 31 and 32 is δ, the height of the columnar portion 33 is (H−δ). In the present embodiment, the height difference δ is set to be equal to or less than the wavelength λ ₁ of the radiated light in the columnar portions 31, 32, 33 in order to form a light beam with good directivity by light interference. preferably, it is more preferably half or less of the wavelength lambda ₁ is obtained as the result of the experiment.

Here, the wavelength λ ₁ is a wavelength when light having the wavelength λ ₀ propagates in the free space through the columnar portions 31, 32, and 33 as an optical waveguide. In general, the dielectric constant of semiconductors and dielectrics is higher than that of air (or vacuum), so the speed of light when propagating in semiconductors and dielectrics is faster than the speed of propagation in air. Become slow. Specifically, when the velocity of light in the air (or in vacuum) is c, and the refractive index of a material such as a semiconductor or a dielectric constituting the columnar portions 31, 32, 33 is n, the columnar portions 31, 32, The speed of light propagating through 33 is given by c / n.

Therefore, the wavelength λ ₁ can be obtained by dividing the value of the wavelength λ ₀ by the refractive index n inside the columnar portions 31, 32, 33. For example, the light emitting structure 2 (see FIG. 1) is made of a GaN-based semiconductor, emits blue light having a wavelength λ ₀ of 405 nm, and the columnar portions 31, 32, and 33 are made of GaN having a refractive index n = 2.6. In this case, the wavelength λ ₁ of the light propagating through the columnar parts 31, 32, 33 is about 156 nm.
In the following description, when the emission direction is specified by the columnar portions 31, 32, 33, the columnar portions 31, 32 may be referred to as a waveguide column and the columnar portion 33 may be referred to as a control column due to a difference in function.

(Reciprocal relationship between light emitting region and columnar part)
Next, referring to FIG. 8 (refer to FIGS. 1 and 2 as appropriate), the mutual relationship between the dimensions of the light emitting region 22a and the dimensions of the columnar parts 31, 32, 33 will be described.
In the following description, for the sake of simplicity, the n-type semiconductor layer 23 and the emission direction specifying portion 3 will be described as being made of a material having the same refractive index. In the case where the light emitting region 22a is made of a material having a different refractive index, Ls calculated by the above equation (6) is used as the dimension of the light emitting region 22a instead of the diameter Lp.

  As described above, in the light emitting element 1, the light emitted from the light emitting region 22 a enters the columnar portions 31, 32, 33 through the n-type semiconductor layer 23 and propagates through the columnar portions 31, 32, 33. Thus, a light beam is formed by interference of light emitted from the upper surfaces 31a, 32a, and 33a that are emission surfaces. Therefore, the intensity of the light beam formed by the interference of the light emitted from the upper surfaces 31a, 32a, 33a of the columnar portions 31, 32, 33 is such that the light emitted from the light emitting region 22a is inside the columnar portions 31, 32, 33. It depends on the amount taken. If the amount of light emitted from the light emitting region 22a is taken into the columnar portions 31, 32, and 33 is less than a certain amount, sufficient intensity from the upper surfaces 31a, 32a, 33a of the columnar portions 31, 32, 33 is obtained. Light is not emitted, and it becomes difficult to form a clear light beam due to interference of these lights.

  On the other hand, in order to improve the arbitrary control of the direction of the light beam emitted from the upper surfaces 31a, 32a, 33a of the columnar portions 31, 32, 33, light is emitted from the light emitting region 22a and the columnar portions 31, 32, 33 are made incident. The light leaking from the element surface (the exposed upper surface 30a of the bottom 30) and the light incident on the columnar portions 31, 32, 33 and emitted from the upper surfaces 31a, 32a, 33a cause extra interference. It is necessary to suppress this.

  In order to achieve both of these, the dimensions of the light emitting region 22a and the columnar portions 31, 32, 33 are set so that the relationship described below is established between the light emitting region 22a and the columnar portions 31, 32, 33. It is desirable to define the dimensions.

As shown in FIG. 8, first, a planar figure drawn so as to be in contact with a part of the outer edges of the columnar parts 31, 32, 33 so as to surround all three columnar parts 31, 32, 33 is assumed. Here, a circular figure surrounding all of the columnar parts 31, 32, 33 is assumed as a planar figure as shown by a two-dot chain line in FIG. 8. The center of this circle coincides with the origin M, which is the center of gravity of an equilateral triangle having vertices at the centers O ₁ , O ₂ , and O ₃ of the columnar portions 31, 32, and 33 (see FIG. 7). Here, the radius _{r SO} of the smallest circle enclosing all the columnar portion 31, 32, the distance ρ from the origin M to the columnar portion 31, 32, 33, the diameter 2φ of the columnar portion 31, 32, 33 added It will be.

Therefore, as shown in FIG. 8, the area SO of the smallest circle (drawn with a two-dot chain line) that surrounds all the columnar parts 31, 32, 33, the area SL of the light emitting region 22a (drawn with a broken line), and the columnar part 31 , 32, and 33 can be obtained from Expressions (7) to (9), respectively.
SL = πΨ ² (7)
SO = π (2φ + ρ) ² (8)
SP = πφ ² Formula (9)

Here, Ψ in equation (7) is the radius of the light emitting region 22a.
At this time, it is desirable that the relationship of Expression (10) is established between the area SL of the light emitting region 22a and the area SO of the smallest circle surrounding all the columnar portions 31, 32, and 33.
SL ≦ SO (10)

In addition, it is desirable that the relationship of Expression (11) is established between the area SL of the light emitting region 22a and the area 3SP that is the sum of the areas SP of the columnar portions 31, 32, and 33.
3SP <= SL ... Formula (11)

In Expression (11), the number to be multiplied by the area SP varies depending on the number of columnar portions installed.
Therefore, when these are put together, it is desirable that the relationship shown in Expression (12) is satisfied in order to achieve both the improvement of the clarity of the light beam and the improvement of the arbitrary control of the light beam direction.
N × SP ≦ SL ≦ SO (12)
However, N shows the installation number of the columnar part and is an integer of 3 or more.

As shown in the equation (12), by setting the area SL of the light emitting region 22a to be equal to or smaller than the area SO of the smallest circle that surrounds all the columnar portions 31, 32, 33, light emitted from the light emitting region 22a can be obtained. The light leaking from the element surface (the exposed upper surface 30a of the bottom 30) other than the columnar parts 31, 32, 33 and emitted from the upper surfaces 31a, 32a, 33a (see FIG. 1) of the columnar parts 31, 32, 33 Since it is possible to suppress the occurrence of excessive interference, it is possible to improve the arbitraryness of the direction control of the light beam.
In plan view, the area SL of the light emitting region 22a is the same as the area of the p-side electrode 24 as described above, more precisely the area where the upper surface of the p-side electrode 24 and the lower surface of the p-type semiconductor layer 21 are in contact with each other. Can be considered.

  Further, as shown in the equation (12), by setting the area SL of the light emitting region 22a to an area 3SP or more, which is the sum of the areas SP of the columnar portions 31, 32, 33, light emitted from the light emitting region 22a Most of the light can enter the columnar portions 31, 32, and 33. For this reason, the intensity | strength of the light which propagates the inside of the columnar parts 31, 32, 33, and is radiate | emitted from the upper surfaces 31a, 32a, 33a can be made high. Thereby, the clarity of the light beam formed by the interference of these lights can be improved.

[Principle of interference of light emitted from columnar portion of light emitting element]
Next, with reference to FIG. 9, an appropriate formula is used to explain the principle of interference of light emitted from the columnar portions 31, 32, 33 of the light emitting element 1, which is a principle for specifying the direction of the light emitted from the light emitting element 1. Will be described. In addition, since the columnar part 31 and the columnar part 32 have the same height, in description using FIG. 9 and numerical formula, it radiate | emits from the two columnar parts 32 and the columnar part 33 from which height differs for the sake of simplicity. An example of light interference will be described.

In the light-emitting element 1 shown in FIG. 9, the exposed upper surface 30a of the bottom 30 is set as a reference position (altitude h ₀ ). Further, altitude h ₁ the position of the upper surface 33a which is the light exit surface of the columnar portion _33, the position of the upper surface 32a which is the light exit surface of the columnar portion 32 and altitude h _2, the columnar portion 32 and the columnar portion 33 Let p be the horizontal interval. Further, in the horizontal position equidistant from the central axis of the columnar portions 32 and 33, and altitude h ₃ of the predetermined point C of the exposed flat upper surface 30a in the vertical axis direction of the bottom portion 30 (drawn in dashed-dotted line) . At this time, the height H of the columnar part 32 is h ₂ −h ₀ , and the height (H−δ) of the columnar part 33 is h ₁ −h ₀ . Accordingly, the difference in height between the columnar portion 32 and the columnar portion 33 is δ = h ₂ −h ₁ .

  As shown in FIG. 9, the light emitted from the light emitting region 22 a in the light emitting element 1 branches into a high columnar portion 32 and a low columnar portion 33 and is emitted from the upper surfaces 32 a and 33 a of the respective columnar portions 32 and 33. The Here, when passing through the high columnar portion 32, the point C passes through the point A1 in the columnar portion 32 and the center point A2 of the upper surface 32a of the columnar portion 32 as one optical path (hereinafter referred to as optical path A). Assume an optical path to reach. Further, when passing through the low columnar portion 33, as one optical path (hereinafter referred to as “optical path B”), the point C passes through the center point B 1 of the upper surface 33 a of the columnar portion 33 and the position B 2 higher than the point B 1 by δ. Assume an optical path to reach.

The light passing through the optical path A and the light passing through the optical path B stay in the same phase because they travel through the medium having the same refractive index (exit direction specifying unit 3) by the same distance up to the height h ₁ . When the phase of the time the initial phase theta _0, the phase in the optical path A point A1 is theta _0, the phase in the optical path point B1 B, is theta _0.

The light passing through the optical path A and the light passing through the optical path B travel through different media from the altitude h ₁ to the altitude h ₂ . At this time, in the optical path A, the medium is a columnar portion 32 (for example, a semiconductor or a dielectric), and in the optical path B, the medium is air. Generally, since the dielectric constant of a semiconductor or a dielectric is higher than that in air (or in a vacuum), the speed of light when propagating in the semiconductor or dielectric is slower than the speed of propagating in air. Specifically, if the velocity of light in the atmosphere (or vacuum) is c and the refractive index of the semiconductor or dielectric is n, the velocity in the semiconductor or dielectric is given by c / n (for example, with GaN). For example, n = 2.6). For this reason, the light generated in the light emitting element 1 made of a semiconductor or a dielectric material is split into two, one is directly emitted into the atmosphere (or in a vacuum), and the other is propagated in the semiconductor or the dielectric. When the light is emitted after the two light beams are emitted, the optical paths are different when they are encountered after the two light beams have been emitted, so that the phases of the light beams are different. Therefore, when the wavelength in the free space of the light from the light emitting element 1 shown in FIG. 9 is λ ₀ and the phase advances by α in the semiconductor or dielectric in the section from the height h ₁ to the height h ₂ in the optical path A. Then, in the optical path A, the phase is represented by Expression (13) at the point A2.

Further, assuming that the phase advances by β in the free space from the height h ₁ to the height h _{2 in} the optical path B, the phase in the optical path B is expressed by Expression (14) at the point B2.

Since more free space from the altitude h ₂ to advanced h _3, the light passing through the light and the optical path B passing through the optical path A travels the same medium (free space). At this time, the distance from the point A2 to the point C on the optical path A and the distance from the point B2 to the point C on the optical path B are the same. Therefore, the difference between the phase at the point A2 of the light passing through the optical path A and the phase at the point B2 of the light passing through the optical path B is also preserved at the point C. This phase difference τ is expressed by Expression (15). That is, the phase difference τ between the optical path A and the optical path B can be controlled by the height difference δ between the columnar section 32 and the columnar section 33. When the equation (15) is transformed, the height difference δ is expressed by the equation (16).

  Since the light passing through the columnar part 32 is delayed as compared with the light passing through the columnar part 33, when both are mixed, a wave having a completely different wavefront from the wavefront of the two lights is generated. That is, the wave fronts of the light emitted from the columnar portions 32 and 33 interfere with each other, and light is transmitted in an azimuth (direction) determined by the relative position (position in the three-dimensional space) of the two columnar portions 32 and 33. Will be injected.

Next, interference of light emitted from the columnar part 32 as the wave source at the position r ₁ in the three-dimensional space and the columnar part 33 as the wave source at the position r ₂ in the three-dimensional space will be described.
The intensity I (r) of light synthesized at the time t at the position r in the three-dimensional space by the light emitted from the wave source at the position r ₁ and the wave source at the position r ₂ is expressed by the following equation (17 ).

In Expression (17), since there is a third term representing the interference of light, the light emitted from the light emitting region 22a is superimposed after being emitted from the two wave sources, and the wave travels by changing the wavefront. The direction can be changed. In equation (17), the real part of γ in equation (18) is used. E ^{* in the} formula (18) indicates a complex conjugate of E. As shown in Expression (18), γ takes a value from 0 to 1, and indicates how much the light emitted from the two wave sources is correlated in time and space. Therefore, γ can be divided into cases as shown in the following equations (19) to (21).

The case of Equation (19) is called fully coherent, the case of Equation (20) is called incoherent, and the case of Equation (21) is called partial coherent. Here, since the light source of LED is used as the light emitting element 1, it is partially coherent. Therefore, in the light-emitting element 1 shown in FIG. 9, since the contribution of the third term of the formula (17) is large in the light intensity, the light traveling direction is greatly bent.
When the horizontal interval p between the columnar portions 32 and 33 is very small, the magnitude of the bending of the light traveling direction is a factor that is dominant due to the height difference δ between the columnar portion 32 and the columnar portion 33. It becomes.

  In FIG. 9, for the sake of simplicity, the direction of the light beam due to the interference of the light emitted from the two columnar portions having different heights has been described. Even when there are three columnar portions as wave sources, it is possible to extend Equation (17). For example, the combination of the first columnar part 31 and the second columnar part 32 is applied as the two wave sources, and the above-described formula (17) is applied, and the combination of the second columnar part 32 and the third columnar part 33 is determined. The above-described equation (17) is applied as two wave sources, the above-described equation (17) is applied using the combination of the third columnar portion 33 and the first columnar portion 31 as two wave sources, and these three combinations are By adding, a relational expression for the case where there are three columnar portions as wave sources can be obtained.

[Method for Manufacturing Light-Emitting Element]
Next, a method for manufacturing the light emitting device according to this embodiment will be described.
Here, a method for manufacturing a display panel in which a plurality of light emitting elements are two-dimensionally arranged will be described with reference to FIGS. 10 to 13 (see FIGS. 1 and 2 as appropriate). In this example, a case where an LED structure is formed using a GaN-based compound semiconductor as the light emitting structure 2 will be described.

(Board preparation process)
First, in the substrate preparation process, as shown in FIG. 10, the substrate 11 in which the p-side electrodes 24 are arranged at the arrangement interval of the light emitting elements 1 is manufactured. The p-side electrode 24 is a columnar electrode. The substrate 11 is a support substrate that supports the light-emitting elements 1 in a two-dimensional arrangement (3 × 3 in the example shown in FIG. 10) and uses an insulating material such as glass, ceramics, or resin. Can do. The substrate 11 is provided with through holes (not shown), and a columnar p-side electrode 24 is inserted into each through hole. 10A, wiring electrodes 12 extending in the vertical direction are arranged in stripes, and each wiring electrode 12 is arranged in a row of p arranged in the extending direction. The side electrode 24 is electrically connected. For the wiring electrode 12, after the p-side electrode 24 is arranged on the substrate 11, a mask is provided between the wiring electrodes on the back side of the substrate 11, and a plating method, vapor deposition method, sputtering method, CVD (chemical vapor deposition) method is used. It can be formed using a conductive material such as metal by a known method such as.
Also, as shown in FIG. 10B, resin or the like is exposed on the upper surface side of the substrate 11 so that the tip of the p-side electrode 24 that is a portion in contact with the p-type semiconductor layer 21 of the light emitting structure 2 is exposed. The insulating layer 13 is formed by applying the insulating material.

Instead of inserting the columnar p-side electrode 24 into the through hole, the through hole is filled with a conductive material such as a low melting point metal or a conductive resin so as to protrude from the through hole, and the conductive material protruding from the through hole. Can also be formed into a hemispherical shape or a conical shape using a mold (see, for example, Reference 3).
Alternatively, the columnar p-side electrode 24 may be protruded from the back surface side of the substrate 11 without providing the stripe-shaped wiring electrodes 12 to form a PGA (Pin Grid Array) type display panel.
(Reference 3): Japanese Patent Laid-Open No. 2002-252456

(Light emitting structure preparation process)
In parallel with the production of the substrate 11 on which the p-side electrodes 24 are arranged, in the light emitting structure preparing step, the light emitting structure 2 is prepared as shown in FIG.
The light emitting structure 2 is formed on a substrate 50 made of sapphire, AlN, GaAs, SiC, Si, or the like by, for example, a film forming method such as MBE (molecular beam epitaxy) method or MOCVD (metal organic chemical vapor deposition) method. The peeling layer 51, the n-type semiconductor layer 23, the light emitting layer 22, and the p-type semiconductor layer 21 can be sequentially stacked.

Note that the peeling layer 51 is a substrate 50 used for growing the light emitting structure 2 which is a semiconductor layer in the peeling step described later after bonding the substrate 11 and the light emitting structure 2 in the bonding step described later. It is a layer for peeling off. For example, when the substrate 50 is peeled off by the laser lift-off method, for example, the base layer when forming the n-type semiconductor layer 23 can be used as the peeling layer 51 (see, for example, Reference 4). This peeling layer 51 is decomposed by laser irradiation in a peeling process described later, and the substrate 50 can be peeled from the light emitting structure 2.
(Reference 4): Japanese Patent No. 4653804

When the substrate 50 is peeled off by the chemical lift-off method, a nitride layer of a metal layer such as Cr can be formed on the substrate 50 as the peeling layer 51 (see, for example, Reference 5). ). The peeling layer 51 made of the metal nitride is removed by chemical etching using a liquid agent in a peeling process described later, and the substrate 50 can be peeled from the light emitting structure 2. Compared with the laser lift-off method, the chemical lift-off method is high in productivity because it can process a large number of wafers at the same time. Also, the yield is high because there is less stress on the semiconductor layer during peeling and the generation of cracks is suppressed. Is expensive.
The release layer 51 made of metal nitride can be formed on the substrate 50 by MOCVD. As another method, after forming a metal film on the substrate 50 by sputtering or vapor deposition, the metal film is nitrided in an ammonia-containing gas atmosphere at a temperature of 1040 ° C. or more to form a metal nitride film. You can also
(Reference 5): JP 2009-54888 A

(Lamination process)
Next, in the bonding step, as shown in FIG. 11B, the light emitting structure 2 produced in the light emitting structure preparing step is brought into contact with the p-type semiconductor layer 21 and the tip of the p-side electrode 24. Paste to. In the bonding step, for example, the substrate 11 provided with the p-side electrode 24 and the insulating layer 13 and the light emitting structure 2 are fused by heating to about 300 ° C. while applying pressure between the substrate 11 and the substrate 50. Let

(Peeling process)
Next, in the peeling step, the substrate 50 is peeled from the light emitting structure 2 as shown in FIG.
In the case of peeling by the laser lift-off method described above, the GaN underlayer of the peeling layer 51 is irradiated with, for example, a nanosecond pulse of an excimer laser of near-ultraviolet light to decompose GaN, and the substrate 50 is separated from the light emitting structure 2. Can be peeled off.
Moreover, when peeling by the above-described chemical lift-off method, the metal nitride layer which is the peeling layer 51 can be removed by chemical etching using a liquid agent, and the substrate 50 can be peeled from the light emitting structure 2. For example, when the metal nitride is CrN, a mixed liquid of perchloric acid and dicerium ammonium nitrate can be used as an etching liquid.

  By performing the bonding process and the peeling process, the light emitting structure 2 is transferred from the substrate 50 to the substrate 11 and sequentially from the lower layer side close to the substrate 11, the p-type semiconductor layer 21, the light emitting layer 22, and the n-type semiconductor. The layer 23 is laminated.

(Outgoing direction specific part forming layer forming step)
Next, in the emission direction specifying portion forming layer forming step, the emission direction specifying portion 3 (see FIG. 1) is formed on the n-type semiconductor layer 23 which is the uppermost layer of the light emitting structure portion 2 as shown in FIG. The emission direction specifying part forming layer 34, which is a layer for forming the film, is formed. The emission direction specifying part forming layer 34 may be formed using a GaN-based compound similar to the n-type semiconductor layer 23, or may be formed using a dielectric such as SiO ₂ or Al ₂ O ₃ .
For example, when the emission direction specifying portion forming layer 34 is formed using a material having a lower refractive index than the n-type semiconductor layer 23 made of a GaN-based semiconductor material, such as SiO ₂ , the columnar portions 31, 32, 33 are formed. The height accuracy can be relaxed.
The emission direction specifying portion forming layer 34 can be formed using the above-described material by a CVD method, a sputtering method, or the like.
When a part of the n-type semiconductor layer 23 formed in the light emitting structure preparation step (upper part in FIG. 12A) is used as the emission direction specification part formation layer 34, the emission direction specification part formation layer formation step is omitted. can do.

(Structure formation process)
Next, in the emission direction specifying portion forming step, as shown in FIG. 12B, the emission direction specifying portion forming layer 34 is processed to form the structure 3 a including the columnar portions 31, 32, 33. In the processing of the emitting direction specifying portion forming layer 34, regions where the columnar portions 31, 32, 33 are formed are masked, and other regions are dry etched such as RIE (reactive ion etching) or wet etching using a chemical solution. Can be used. At this time, the mask formed in the region where the columnar portions 31 and 32 are formed and the mask formed on the columnar portion 33 are made different in thickness so that one of the masks is quickly removed by etching, and the emission direction is specified. By making a part of the part forming layer 34 etched, the columnar parts 31 and 32 and the columnar part 33 can be formed to have different heights.
Further, in a step different from the etching of the region where the columnar portions 31, 32, 33 are formed, a mask is formed on the columnar portion to be formed higher, and the upper portion of the columnar portion where the mask is not formed is etched, whereby the columnar portions 31, 32 are formed. And the columnar portion 33 can be formed to have different heights.

(Separation groove forming process)
Next, in the separation groove forming step, as shown in FIG. 12C, the direction (row direction) perpendicular to the direction in which the wiring electrodes 12 extend (column direction) extends to the emission direction specifying portion 3 and the light emitting structure portion 2. ) Is formed to separate the light emitting element 1. The separation groove 52 can be formed by masking and etching other than the region where the separation groove 52 is formed.

Note that an insulating protective film such as SiO ₂ may be formed inside the separation groove 52 or on the surface of the light emitting element 1 after the formation of the separation groove 52.

(N-side electrode forming step)
Next, in the n-side electrode forming step, as shown in FIGS. 13A and 13B, the n-type semiconductor layer 23 is formed for each row of the light-emitting elements 1 separated by the separation grooves 52. An n-side electrode 25 that contacts a part of the side surface is formed.
The n-side electrode 25 can be formed by a sputtering method, a vapor deposition method, or the like using a conductive material such as a metal or a conductive compound while masking a region other than the region where the n-side electrode 25 is formed.

As described above, when the carrier mobility in the n-type semiconductor layer 23 is sufficiently larger than the carrier mobility in the p-type semiconductor layer 21 and the recombination time is sufficiently shorter than the carrier diffusion time, By providing the n-side electrode 25 in a part of the n-type semiconductor layer 23, carriers can be diffused substantially uniformly in the n-type semiconductor layer 23.
In this example, as shown in FIG. 13B, an n-side electrode is formed on a part of the right side surface of the n-type semiconductor layer 23 for each of the plurality of light emitting elements 1 arranged in one row in the row direction (lateral direction). 25 is provided. Accordingly, a row in the display panel 10 can be selected by selecting one n-side electrode 25 to which a voltage is applied (that is, a signal is input). Further, by selecting one wiring electrode 12 to which a voltage is applied, a column in the display panel 10 can be selected. That is, by selecting one n-side electrode 25 and one wiring electrode 12, one light-emitting element 1 that controls light emission can be selected.

  When a part of the n-type semiconductor layer 23 is used as the emission direction specifying part forming layer 34, the n-side electrode 25 may be provided so as to be in contact with a part of the emission direction specifying part 3.

  As described above, the light emitting element 1 according to the embodiment of the present invention can form a light beam by the light interference effect by forming three or more columnar portions on the surface. In addition, the light emitting element 1 appropriately adjusts the arrangement of the columnar portions 31, 32, and 33 in the emission direction specifying portion 3 and the height difference between the columnar portion 33 that is the control column and the columnar portions 31 and 32 that are the waveguide columns. Thus, it is possible to form a light beam radiating in an arbitrary direction including a direction perpendicular to the display panel surface. Moreover, since the light emitting element 1 can control the direction of the light beam only by forming the columnar portions 31, 32, 33 on the surface, the structure thereof is simple.

<Modification of First Embodiment>
Next, a modification of the first embodiment will be described with reference to FIG.
A light-emitting element 1A according to a modification of the first embodiment shown in FIG. 14 is configured by including an n-side electrode 25A instead of the n-side electrode 25 in the light-emitting element 1 according to the first embodiment shown in FIG. Is. About the structure similar to the light emitting element 1 which concerns on 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted suitably.

  As shown in FIG. 14, the light emitting element 1 </ b> A according to this modification is an upper surface 30 a of the bottom 30 of the emission direction specifying unit 3, and a region where the structure 3 a is provided in plan view (in FIG. 14, a columnar part An n-side electrode 25A is provided so as to surround the structure 3a in a region excluding a circumscribed circle including 31, 32, and 33).

In this modification, the carrier mobility in the n-type semiconductor layer 23 is not sufficiently large compared to the carrier mobility in the p-type semiconductor layer 21 or the recombination time is not sufficiently short compared to the carrier diffusion time. The n-side electrode 25A is arranged so as to be suitable for the above.
By providing the n-side electrode 25A so as to surround the light emitting region 22a as described above, the shape of the light emitting region 22a can be determined by the shape of the p side electrode 24. That is, the vicinity of the region directly above the p-side electrode 24 can be the light emitting region 22a.

  When the n-side electrode 25A is provided so as to be in contact with the emission direction specifying portion 3 as in this example, is the emission direction specifying portion 3 formed by processing the upper part of the n-type semiconductor layer 23? And a light-transmitting conductive material such as ITO. Thus, the n-side electrode 25A and the n-type semiconductor layer 23 can be electrically connected. In particular, when the emission direction specifying portion 3 is configured using a conductive material, the entire emission direction specifying portion 3 functions as an extended electrode of the n-side electrode 25A, and thus the n-type semiconductor layer 23 has a more uniform current. Can be diffused.

  Further, an electrode having a uniform thickness is formed between the n-type semiconductor layer 23 and the emission direction specifying portion 3 by using a light-transmitting conductive material such as ITO so as to cover the entire upper surface of the n-type semiconductor layer 23. A layer may be formed, and the n-side electrode 25A may be provided so as to be in contact with the electrode layer. With this configuration, the current supplied from the n-side electrode 25A can be uniformly diffused into the n-type semiconductor layer 23 via the translucent electrode layer. Further, by making the film thickness of the translucent electrode layer uniform, there is no phase difference in the light incident on the columnar parts 31, 32, 33 of the emission direction specifying part 3, so that the emission direction is specified. There is no restriction on the material selection and the degree of freedom of the structure of the portion 3.

  In addition, as an electrode layer provided between the n-type semiconductor layer 23 and the emission direction specifying portion 3, a light-transmitting conductive material is used in the region immediately above the p-side electrode 24, and the other regions have the same thickness as the region immediately above. You may make it form using conductive materials, such as a metal with better electroconductivity than a translucent conductive material. Accordingly, current can be supplied better than in the case where the electrode layer is formed using only a light-transmitting conductive material, so that stronger light can be emitted.

Since the light emitting element 1A according to the present modification operates in the same manner as the light emitting element 1 according to the first embodiment except that the arrangement of the n-side electrode 25A is different, the description of the operation is omitted.
Further, in the light emitting element 1A according to this modification, in the method for manufacturing the light emitting element 1 according to the first embodiment, the position where the mask for forming the n-side electrode 25 is provided corresponds to the position where the n-side electrode 25A is provided. Therefore, detailed description is omitted because it can be formed in the same manner.

Second Embodiment
Next, with reference to FIG.15 and FIG.16, the light emitting element which concerns on 2nd Embodiment is demonstrated.
As shown in FIGS. 15 and 16, the light emitting device 1 </ b> B according to the second embodiment is different from the light emitting device 1 according to the first embodiment shown in FIGS. The direction specifying unit 3B is provided. About the structure similar to the light emitting element 1 which concerns on 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted suitably.

  As shown in FIGS. 15 and 16, the light emitting element 1 </ b> B has three or more holes (columnar recesses) as the structure 3 </ b> Ba so as to surround a predetermined region on the flat upper surface 40 a, and includes at least one hole. The depth is different from others, and it is characterized in that light is emitted from all these holes. In the following description, it is assumed that the light emitting element 1 </ b> B has three holes 41, 42, 43 as an example, and the hole 43 is shallower than the holes 41, 42.

The light-emitting element 1B according to the present embodiment has three columnar recesses (columnar recesses) 41, 42, and 43 as the structure 3Ba as the emission direction specifying portion 3B. The holes 41, 42, and 43 are structures that replace the columnar portions 31, 32, and 33 of the emission direction specifying portion 3 in the first embodiment. As described above, the depth of the bottom surface 43a of the hole 43 is shallower than the depth of the bottom surfaces 41a and 42a of the holes 41 and 42 with respect to the upper surface 40a of the emission direction specifying portion 3B.
In the present embodiment, the shape of the holes 41, 42, 43 is a columnar shape having a circular cross section, but is not limited to this, and the cross section is a columnar shape having another shape such as a polygon or an ellipse. You can also.

Light emitted from the light emitting region 22a of the light emitting structure 2 enters the holes 41, 42, and 43, and exits from the bottom surfaces 41a, 42a, and 43a of the holes 41, 42, and 43, and these emitted lights interfere with each other. A light beam having an intensity in a direction corresponding to the arrangement of the holes 41, 42, 43 is emitted from the emission direction specifying unit 3B. The emission direction specifying part 3B makes the depths of the holes 41, 42, and 43 different from each other, and the phase difference between the light emitted from the bottom surfaces 41a, 42a, and 43a of the holes 41, 42, and 43 due to the difference in the depths. It will cause.
The principle of specifying the light emission direction by the emission direction specifying unit 3B is the same as that of the emission direction specifying unit 3 in the first embodiment, and thus the description thereof is omitted. The operation of the light emitting structure 2 is also the same as that of the light emitting structure 2 in the first embodiment, and a description thereof will be omitted.

Further, the preferable relationship between the light emitting region 22a in the plan view and the arrangement of the holes 41, 42, 43 is the same as that of the light emitting region 22a and the columnar portions 31, 32, 33 in the light emitting element 1 according to the first embodiment. . That is, assuming that the area of the light emitting region 22a is SL, the area of the holes 41, 42, 43 is SP, and the area of the circumscribed circle including the holes 41, 42, 43 is SO, the clarity of the light beam is improved and the direction control of the light beam is performed. In order to achieve both improvement in the arbitraryness of the above, it is desirable that the relationship of the above-described formula (12) is satisfied.
However, in Formula (12), N shall show the number of installation of a hole, and is an integer greater than or equal to 3.

  Further, the light emitting device 1B according to the present embodiment has a hole 41 instead of providing a mask for forming the columnar portions 31, 32, 33 in the structure forming step in the method for manufacturing the light emitting device 1 according to the first embodiment. , 42, 43 can be manufactured by providing a mask in areas other than the region where holes are formed, and forming the holes 41, 42, 43 by etching. Since this step is the same as that of the first embodiment, description thereof is omitted.

<Modification of Second Embodiment>
Next, a modification of the second embodiment will be described with reference to FIG.
A light emitting device 1C according to a modification of the second embodiment shown in FIG. 17 includes an n side electrode 25C instead of the n side electrode 25 in the light emitting device 1B according to the second embodiment shown in FIG. Is. About the structure similar to the light emitting element 1B which concerns on 2nd Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted suitably.

  The light emitting element 1C in the present modification is the upper surface 40a of the emission direction specifying part 3A, like the n-side electrode 25A of the light emitting element 1A according to the modification of the first embodiment shown in FIG. The n-side electrode 25C is provided so as to surround the structure 3Ba in a region excluding the region where the structure 3Ba is provided (in FIG. 17, the inner region of the circumscribed circle including the holes 41, 42, and 43 in plan view). is there.

In this modification, the carrier mobility in the n-type semiconductor layer 23 is not sufficiently large compared to the carrier mobility in the p-type semiconductor layer 21 or the recombination time is not sufficiently short compared to the carrier diffusion time. The n-side electrode 25C is disposed so as to be suitable for the above.
By providing the n-side electrode 25C so as to surround the light emitting region 22a as described above, the shape of the light emitting region 22a can be determined by the shape of the p side electrode 24. That is, the vicinity of the region directly above the p-side electrode 24 can be the light emitting region 22a.

  When the n-side electrode 25C is provided so as to be in contact with the emission direction specifying portion 3B as in this example, is the emission direction specifying portion 3 formed by processing the upper part of the n-type semiconductor layer 23? And a light-transmitting conductive material such as ITO. Thereby, the n-side electrode 25C and the n-type semiconductor layer 23 can be electrically connected.

  Further, an electrode having a uniform thickness is formed between the n-type semiconductor layer 23 and the emission direction specifying portion 3B by using a light-transmitting conductive material such as ITO so as to cover the entire upper surface of the n-type semiconductor layer 23. A layer may be formed, and the n-side electrode 25C may be provided so as to be in contact with this electrode layer. With this configuration, the current supplied from the n-side electrode 25C can be uniformly diffused into the n-type semiconductor layer 23 via the translucent electrode layer. Further, by making the film thickness of the translucent electrode layer uniform, the phase difference of the light incident on the columnar recesses 41, 42, 43 of the emission direction specifying portion 3B is not changed, so that the emission direction is specified. There is no restriction on the material selection or the structural freedom of the portion 3B.

  In addition, as an electrode layer provided between the n-type semiconductor layer 23 and the emission direction specifying portion 3B, a light-transmitting conductive material is used in the region immediately above the p-side electrode 24, and the other regions have the same thickness as the region immediately above. You may make it form using conductive materials, such as a metal with better electroconductivity than a translucent conductive material. Accordingly, current can be supplied better than in the case where the electrode layer is formed using only a light-transmitting conductive material, so that stronger light can be emitted.

Since the light emitting element 1C according to this modification operates in the same manner as the light emitting element 1B according to the second embodiment except that the arrangement of the n-side electrode 25C is different, the description of the operation is omitted.
Further, in the light emitting element 1C according to this modification, in the method for manufacturing the light emitting element 1B according to the second embodiment, the position where the mask for forming the n-side electrode 25 is provided corresponds to the position where the n-side electrode 25C is provided. Therefore, detailed description is omitted because it can be formed in the same manner.

<Third Embodiment>
[Concept of IP stereoscopic display]
Next, with reference to FIG. 18 and FIG. 19, an IP stereoscopic display (stereoscopic image display apparatus) using the light emitting element of the present invention will be described as a third embodiment.
As shown in FIGS. 18A and 18B, the IP stereoscopic display according to the present embodiment is an IP display by arranging a large number of light-emitting elements 1 according to the first embodiment on a substrate 11. A certain IP stereoscopic display 100 is configured. Although illustration is omitted, an IP stereoscopic imaging device corresponding to the IP stereoscopic display 100 may acquire an element image group in which a subject such as a cylinder or a cube illustrated in FIG. Although it is convenient for displaying (reproducing) a three-dimensional object, it is created by multi-view video or a three-dimensional model rendering process, and the data is configured according to the arrangement of the light emitting elements 1 in the IP three-dimensional display 100. You may use.

In a conventional IP display, for example, an element image group is displayed on a liquid crystal panel, and each element image is simply projected through each element lens of an element lens array similar to that at the time of photographing and accumulated. The image can be observed as a stereoscopic reproduction image corresponding to the subject.
In the case of the IP stereoscopic display 100 according to the present invention, a plurality of light emitting elements 1 arranged densely form an element image as a unit pixel group, and correspond to individual element lenses of a conventional IP stereoscopic display. The corresponding element pixel groups (one unit structure) are arranged side by side.

  Here, the element image is an image projected in correspondence with one element lens in a conventional IP system display using an element lens array which is an assembly of minute optical lenses. In a conventional IP display, light rays emitted from each pixel of the element pixel group constituting one element image are emitted in a direction connecting each pixel position and the center of the element lens. For this reason, the light rays emitted from each pixel constituting one set of element pixel groups are emitted in different directions.

In the present invention, in place of the element lens in the conventional IP display, the emission direction is set for each light emitting element 1 used as a pixel. Therefore, in the IP stereoscopic display 100 shown in FIG. 18A, the structure 3 a is installed so that each light emitting element 1 emits a light beam in a predetermined direction.
As described above, it is possible to provide the IP three-dimensional display 100 by arranging a large number of the light emitting elements 1 on the substrate 11. In this case, the light emitting elements 1 themselves are inclined with respect to the substrate 11. By doing so, the emission direction can be set in a wider range.

  FIG. 18B shows an example of the state of light rays emitted from the IP stereoscopic display 100 in the direction of the observation point at a certain observation point. At the observation point, rays (thick arrow lines) emitted in the direction of the observation point in each element pixel group are accumulated, and for example, an image such as a cylinder or a cube can be observed.

  In addition, between the light emitting elements 1 of the IP stereoscopic display 100, that is, between the pixels, since they are arranged with a distance equal to or longer than the coherence length, an interference wave is generated between light emitted from different pixels. There is nothing. Therefore, for example, the intensity of the light synthesized from the light emitted from the three pixels is simply an addition of the intensity of each light emitted from the three pixels. That is, the intensity of the light synthesized between the pixels is obtained by an operation corresponding to the first term and the second term of Equation (17) when the three pixels are regarded as three wave sources. .

  A display panel in which a large number of light emitting elements 1 having such a fine structure are arranged has the same function as a device in which a lens plate and a light emitting surface are joined in the prior art. In the IP stereoscopic display 100 created in this way, the resolution of the stereoscopic display depends only on the definition of the light emitting element 1, and image blur due to insufficient resolution of the optical system does not occur. Further, the maximum value of the viewing zone angle in the IP display using the light emitting element 1 depends only on the maximum value of the angle (control angle) of the radiated light with respect to the direction perpendicular to the element surface, and the resolution and the viewing zone angle are determined. It is possible to improve independently.

[Configuration of IP stereoscopic display]
Next, the configuration of the IP stereoscopic display 100 according to the present embodiment will be described in detail with reference to FIG.
As shown in FIG. 19, the IP stereoscopic display 100 according to the present embodiment includes a display panel (display element) 10 and a drive unit 60. The IP stereoscopic display 100 is a stereoscopic image display device that displays an image signal input via the external display control unit 70 on the display panel 10 as an IP stereoscopic image.

  The display panel (display element) 10 is a display element that is provided with a plurality of light-emitting elements 1 arranged in a two-dimensional manner as pixels, and displays an IP system stereoscopic image. The display panel 10 includes an n-side electrode 25 for each light-emitting element 1 arranged in the row direction (horizontal direction), and for wiring connected to the p-side electrode 24 for each light-emitting element 1 arranged in the column direction (vertical direction). And an electrode 12. That is, the n-side electrode 25 is a common electrode on the n-side of the light emitting elements 1 belonging to one row to which the n-side electrode 25 is connected, and the wiring electrode 12 includes the wiring electrode 12 and the p-side electrode 24. This is a common electrode of the p-side electrode 24 belonging to one connected column.

  A row selection signal, which is a scanning signal, is input to each n-side electrode 25 from the row selection unit 61. In addition, an image signal corresponding to a column position is input to each wiring electrode 12 from the column selection unit 62 as a column selection signal. In the display panel 10, the n-side electrode 25 to which the row selection signal is input and the light emitting element 1 connected to the wiring electrode 12 to which the column selection signal is input are selected, and the light emission time (light emission / non-light emission) is selected. Be controlled.

The drive unit (pixel selection means) 60 includes a row selection unit 61 and a column selection unit 62, and is arranged as a pixel on the display panel 10 based on an image signal input via the external display control unit 70. The light emitting elements 1 are sequentially selected, and the light emission time is controlled.
The row selection unit 61 receives a scanning signal synchronized with the row of the image signal from the display control unit 70, and outputs it to the n-side electrode (row electrode) 25 corresponding to the row. A row to which a row selection signal having a predetermined potential (for example, 0 V) indicating selection is input is a target whose light emission time is controlled.
The column selection unit 62 receives the image signal from the display control unit 70, divides it into image signals corresponding to each column, and uses the image signals divided into the wiring electrodes 12 corresponding to each column in parallel as column selection signals. Output. The light emitting element 1 emits light during a period in which a column selection signal having a predetermined level potential (for example, 5 V) indicating that it has been selected is input. Therefore, the light-emitting element 1 emits light during a period in which the row selection signal is input and a column selection signal of a predetermined level is input, and the light-emitting element 1 does not emit light in other periods. By increasing / decreasing the period of the predetermined level in the column selection signal according to the corresponding pixel data in the image signal, the luminance displayed as the pixel of the light emitting element 1 can be modulated.

  The display control unit 70 inputs an image signal, outputs the input image signal to the column selection unit 62, and outputs a scanning signal synchronized with the image signal to the row selection unit 61 as a row selection signal. .

  In addition, the display panel 10 in this embodiment can be manufactured by the manufacturing method of the display panel 10 demonstrated as a manufacturing method of the light emitting element 1 which concerns on 1st Embodiment.

[Operation of IP stereoscopic display]
Next, the operation of the IP stereoscopic display 100 according to the present embodiment will be described with reference to FIG.
The IP stereoscopic display 100 receives a scanning signal synchronized with the row of the image signal together with the image signal from the display control unit 70. In the IP stereoscopic display 100, the row selection unit 61 sequentially selects the n-side electrode 25 and outputs the scanning signal input from the display control unit 70 as a row selection signal. In parallel with this, the IP stereoscopic display 100 divides the image signal of one row input from the display control unit 70 into the data signals corresponding to the columns by the column selection unit 62, and the divided data signals are respectively Output to the wiring electrode 12 in the corresponding column.
In the display panel 10 of the IP stereoscopic display 100, the light emitting time of each light emitting element 1 belonging to the row selected by the row selecting unit 61 is controlled according to the data signal input from the column selecting unit 62.

When the IP stereoscopic display 100 receives a scanning signal for the next row from the display control unit 70, the IP stereoscopic display 100 outputs a row selection signal for selecting the next row by the row selection unit 61 to the corresponding n-side electrode 25. In parallel with this, the IP stereoscopic display 100 uses the column selection unit 62 to divide the image signal of the next row input from the display control unit 70 into data signals corresponding to the columns, Each is output to the wiring electrode 12 in the corresponding column. Thereby, the light emission time of the light emitting elements 1 belonging to the next row is controlled.
Hereinafter, the IP stereoscopic display 100 controls the light emission times of the light emitting elements 1 belonging to the selected row by sequentially changing the selected row. By repeating this, the IP stereoscopic display 100 can display the image signal input via the display control unit 70 on the display panel 10 as a stereoscopic image.

  In the present embodiment, the light-emitting element 1 according to the first embodiment is used as a pixel. However, the light-emitting element 1A according to the modification of the first embodiment, the light-emitting element 1B according to the second embodiment, or the second embodiment. The light emitting element 1C according to the modified example can also be used as a pixel.

[Possibility of using light emitting elements]
The light-emitting elements 1, 1A, 1B, and 1C of the present invention can be applied to general devices that require light beam shaping and direction control. For example, it is suitable for a light source for a projector, a connector used for spatial light interconnection, an illumination light source that does not require a diffuser.

DESCRIPTION OF SYMBOLS 1, 1A, 1B, 1C Light emitting element 2 Light emitting structure part 3, 3B Output direction specific part 3a, 3Ba Structure 10 Display panel (display element)
11 Substrate 12 Wiring electrode (column electrode)
13 Insulating layer 21 p-type semiconductor layer (first semiconductor layer)
22 light emitting layer 22a light emitting region 23 n-type semiconductor layer (second semiconductor layer)
24 p-side electrode (first electrode)
25, 25A, 25C n-side electrode (second electrode)
30 Bottom portion 30a Upper surface 31, 32 Columnar portion (waveguide column)
33 Columnar part (control column)
31a, 32a, 33a Upper surface 34 Structure portion formation layer 40a Upper surface 41, 42 Hole (columnar recess)
43 holes (control holes) (columnar recesses)
41a, 42a, 43a Bottom 50 Substrate 51 Peeling layer 52 Separation groove 60 Drive unit (pixel selection means)
61 row selection unit 62 column selection unit 70 display control unit 100 IP stereoscopic display (stereoscopic image display device)

Claims (8)

A first semiconductor layer, a light emitting layer, and a second semiconductor layer are stacked in this order, and includes a first electrode connected to the first semiconductor layer, and a second electrode connected to the second semiconductor layer. A light emitting device having a light emitting structure,
An emission direction specifying part having a structure for specifying the direction of light emitted from the light emitting layer on a part of the second semiconductor layer or the upper surface of the second semiconductor layer,
The first electrode is provided directly below the structure and in contact with a part of the lower surface of the first semiconductor layer,
Carrier mobility of the second semiconductor layer is larger than carrier mobility of the first semiconductor layer, and carriers that move in the light emitting layer through the first semiconductor layer and carriers that move through the second semiconductor layer are when radiative recombination to, the recombination time is the time required for recombination, rather short than the relaxation time is a time required for replenishment of carriers extinguished by the recombination,
The structure includes N (N is an integer of 3 or more) columnar portions that emit light from the emission surface of the stigma.
The N columnar portions are arranged in a ring shape within a range in which light emitted from the light emitting layer can interfere in a plan view, and at least one of the N columnar portions has a height other than that. Unlike the height of the column, the difference in height of the columnar part is not more than half of the wavelength of light emitted from the light emitting layer inside the columnar part . In plan view, the light emitting device of claim 1, wherein the area of the first electrode, wherein the or less area of the circumscribed circle surrounding the columnar portion of the N. In plan view, the area of the first electrode, the light emitting device according to claim 1 or claim 2, wherein the at least the sum of the areas of the columnar portion of the N. A first semiconductor layer, a light emitting layer, and a second semiconductor layer are stacked in this order, and includes a first electrode connected to the first semiconductor layer, and a second electrode connected to the second semiconductor layer. A light emitting device having a light emitting structure,
An emission direction specifying part having a structure for specifying the direction of light emitted from the light emitting layer on a part of the second semiconductor layer or the upper surface of the second semiconductor layer,
The first electrode is provided directly below the structure and in contact with a part of the lower surface of the first semiconductor layer,
Carrier mobility of the second semiconductor layer is larger than carrier mobility of the first semiconductor layer, and carriers that move in the light emitting layer through the first semiconductor layer and carriers that move through the second semiconductor layer are when radiative recombination to, the recombination time is the time required for recombination, rather short than the relaxation time is a time required for replenishment of carriers extinguished by the recombination,
The structure is composed of N (N is an integer of 3 or more) columnar recesses recessed in a columnar shape from the upper surface,
The N columnar recesses are provided in a ring shape within a range in which light emitted from the light emitting layer can interfere in a plan view, and the depth of at least one columnar recess among the N columnar recesses is Unlike the other columnar recesses, the difference in depth between the columnar recesses is not more than half of the wavelength of light emitted from the light emitting layer inside the columnar recesses . 5. The light emitting device according to claim 4 , wherein an area of the first electrode is equal to or less than an area of a circumscribed circle surrounding the N columnar recesses when viewed in a plan view. In plan view, the area of the first electrode, the light emitting device according to claim 4 or claim 5, wherein the at least the sum of the areas of the columnar groove portion of the N. The refractive index of the structures, the light emitting device according to any one of claims 1 to 6, characterized in smaller than the refractive index of the second semiconductor layer. On a substrate, a display panel provided by arranging a two-dimensional array of light emission elements as pixels,
Pixel selection means for selecting at least one of the pixels,
The light emitting element is
A first semiconductor layer, a light emitting layer, and a second semiconductor layer are stacked in this order, and includes a first electrode connected to the first semiconductor layer, and a second electrode connected to the second semiconductor layer. Having a light emitting structure
An emission direction specifying part having a structure for specifying the direction of light emitted from the light emitting layer on a part of the second semiconductor layer or the upper surface of the second semiconductor layer,
The first electrode is provided directly below the structure and in contact with a part of the lower surface of the first semiconductor layer,
Carrier mobility of the second semiconductor layer is larger than carrier mobility of the first semiconductor layer, and carriers that move in the light emitting layer through the first semiconductor layer and carriers that move through the second semiconductor layer are When light is emitted by recombination, the recombination time, which is the time required for the recombination, is shorter than the relaxation time, which is the time required for replenishment of carriers annihilated by the recombination,
An integral photography type stereoscopic image display device, wherein the pixel selection unit selects the pixel and controls light emission and non-light emission of the selected pixel.

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