JP4538176B2 - Light emitting diode - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a light emitting diode that can effectively transmit light from a light emitting chip, reduce the electrical resistance of a surface electrode, and efficiently emit polarized light.
[0002]
[Prior art]
  The electrode structure of the light emitting diode is shown in FIGS. The light emitting diode of FIG. 1 is provided with a pair of electrodes 21 on both surfaces of a light emitting chip 20. When the pair of electrodes 21 is connected to a power source, the light emitting chip 20 emits light. When a voltage is supplied to the electrodes 21, the light emitting chip 20 emits light when a current flows between the electrodes. In the drawing, the electrode on the upper surface is a transparent electrode 21 </ b> A and transmits light emitted from the light emitting chip 20. In the light emitting chip 20 of FIG. 2, a bonding electrode 21B is provided on the n layer on the lower surface, and the electrode on the upper surface is used as the transparent electrode 21A. The light emitting chip 20 emits light by applying a voltage to the n layer and the transparent electrode 21A. The light emitted from the light emitting chip 20 is transmitted to the outside through the transparent electrode 20A.
[0003]
[Problems to be solved by the invention]
  Since the transparent electrode needs to transmit light, an electrode having translucency and conductivity such as ITO is used. A transparent electrode such as ITO has a high specific resistance and thus has a large internal resistance, which increases the supply voltage of the light emitting diode. The transparent electrode needs to have a small electric resistance in order for the light emitting chip to emit light at a low voltage. However, a transparent electrode having a small electric resistance has a low light transmittance and reduces the light emission output. An ideal transparent electrode has low electrical resistance and high light transmittance. However, the electrical resistance and light transmittance of the transparent electrode are mutually contradictory properties, and it is difficult to satisfy both. This also increases the cost of the transparent electrode and increases the manufacturing cost of the light emitting diode. In an actual light emitting diode, if the light transmittance of the transparent electrode is lowered, the light emission output is lowered. Therefore, in order to increase the light transmittance of the transparent electrode, the electric resistance must be increased. This makes it difficult to reduce the supply voltage of the light emitting diode.
[0004]
  The present invention has been developed with the object of solving the above-described drawbacks of the related art, and the supply voltage of the light emitting diode can be efficiently taken out while the light emitted from the light emitting chip is efficiently extracted by a structure completely different from the conventional structure. An object of the present invention is to provide a light emitting diode capable of lowering the voltage.
  Furthermore, the second object of the present invention is to provide a light emitting diode capable of efficiently emitting polarized light.
[0005]
[Means for Solving the Problems]
  The light-emitting diode according to claim 1 of the present invention includes a light-emitting chip 1 having a surface electrode 3 on the first surface side, and a second surface on the opposite surface facing the first surface side of the light-emitting chip 1. And a light reflection layer 6 provided on the side. The surface electrode 3 is a metal electrode layer that reflects light on the inner surface, and a plurality of through holes 14 that can transmit light are provided in the surface electrode 3.This through hole 14 is a slit.
[0006]
[0007]
  lightThe reflective layer 6 can have the light reflecting surface 6A as an uneven surface. The light emitting diode reflects light from the light emitting chip 1 with the light reflecting layer 6, polarizes the light from the through hole 14 of the slit, and transmits the light to the surface side of the surface electrode 3.Can be.
[0008]
  The through hole 14 of the slit has a slit width (H) of λ / 10 or more, preferably λ / 5 or more, more preferably λ / 2 or more of the peak wavelength λ of the light emitting wavelength of the light emitting chip 1. Further, the through hole 14 of the slit has a slit length (W) larger than the slit width (H) and the slit length (W) from λ / 2 of the peak wavelength λ of the emission wavelength of the light emitting chip. More preferably larger than the peak wavelength λ. The slit through-hole 14 preferably has a slit length (W) larger than twice the slit width (H).
[0009]
  In the light emitting diode, the light emitting chip 1 can be fixed to a holder, and the light reflecting layer 6 can be provided on the holder. Further, the light emitting diode can be fixed by laminating the light reflecting layer 6 on the second surface side of the light emitting chip. The light reflecting surface 6A of the light reflecting layer 6 can be an uneven surface. The surface electrode 3 can have an aperture ratio of 20 to 80%, preferably 30 to 70%, more preferably 40 to 60%.
[0010]
  Further, in the light emitting diode of the present invention, the dielectric antenna 2 is provided in the slit-like through hole 14. This light-emitting diode collects light in the vicinity of the through-hole 14 by the dielectric antenna 2 and transmits it through the through-hole 14, so that light can be transmitted to the surface side of the surface electrode 3 more efficiently. The dielectric antenna 2 is provided from the surface of the surface semiconductor layer 4 of the light emitting chip 1 toward the inside. The dielectric antenna 2 is provided so as to protrude from the surface of the surface semiconductor layer 4 of the light emitting chip 1.
[0011]
[0012]
  In the light emitting diode, a phosphor layer 9 can be provided between the light emitting chip 1 and the light reflecting layer 6. The phosphor layer 9 preferably converts the wavelength of blue light emission into red or yellow. Further, in the light emitting diode, the nonlinear optical material layer 11 can be provided between the light emitting chip 1 and the light reflecting layer 6. Further, in the light emitting diode, the light emitting chip 1 can be a light emitting chip formed by stacking gallium nitride compound semiconductor layers.
[0013]
  The dielectric antenna 2 has a height (T) of 0.5 to 5 times the maximum peak wavelength λmax of the light emitting chip 1 and a minimum width (D) of 0.5 to 2 times the height. The distance (L) between the antennas 2 is set to 0.5 to 10 times the maximum peak wavelength λmax. The height (T) of the dielectric antenna 2 is preferably 0.5 to 5 μm. Dielectric antenna 2 is,flatIt can be a prismatic shape with a rectangular surface shape or a long columnar shape with arcs at both ends in a planar shape.
[0014]
  The dielectric antenna 2 can be formed of a multilayer dielectric film 10. Dielectric constant of dielectric forming dielectric antenna 2Is 1. 1-10.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
  Embodiments of the present invention will be described below with reference to the drawings. However, the following examples illustrate light-emitting diodes for embodying the technical idea of the present invention, and the present invention does not specify the light-emitting diodes as follows.
[0016]
  Further, in this specification, in order to facilitate understanding of the claims, the numbers corresponding to the members shown in the embodiments are referred to as “claims column” and “means for solving the problems”. It is added to the member shown by. However, the members shown in the claims are not limited to the members in the embodiments.
[0017]
  In the light emitting diode shown in FIGS. 3 and 4, the surface electrode 3 is provided on the first surface side which is the front surface side of the light emitting chip 1, and the light reflecting layer 6 is provided on the back surface side. However, FIG. 3 does not show an embodiment of the present invention, but serves as a reference example.TheIt is described. The surface electrode 3 is a metal electrode layer that reflects light on the inner surface, and a plurality of through holes 14 are opened and light is transmitted through the through holes 14. Therefore, in the light emitting diode of the present invention, the surface electrode 3 is not required to have translucency. The non-translucent surface electrode 3 is a metal electrode layer. Since the metal electrode layer can have an extremely low electrical resistance, a large current can be made to flow uniformly. Also, heat generation due to Joule heat can be reduced. The surface electrode 3 can be a metal thin film made of gold, aluminum, copper, silver or the like, for example. However, it goes without saying that a metal electrode layer that slightly transmits light can be used as the surface electrode 3.
[0018]
  As shown in FIGS. 5 to 7, the through hole 14 of the surface electrode 3 has a circular shape, an elliptical shape, a polygonal shape or the like. However, FIG. 5 and FIG. 6 do not relate to the embodiment of the present invention but are described as reference examples. In these drawings, the surface electrode 3 is represented by cross hatching in order to make the through hole 14 easy to understand. The minimum width of the through hole 14 is, for example, larger than λ / 10 of the peak wavelength λ of the light emitting wavelength of the light emitting chip, preferably larger than λ / 5, more preferably larger than λ / 2, optimally larger than λ. Enlarge. This is because the light emitted from the light emitting diode is efficiently transmitted through the through hole 14. However, if the through-hole 14 is too large, a large number of through-holes 14 cannot be provided in the surface electrode 3, and a current cannot be made to flow uniformly with the surface electrode 3. Therefore, the through-hole 14 has such a size that 10 or more, preferably 50 or more, and optimally 100 or more can be provided in the surface electrode 3.
[0019]
  The surface electrode 3 reflects light at the inner surface and radiates light from the through hole 14 to the outside. Therefore, the surface electrode 3 can increase the transmittance of light by increasing the aperture ratio of the through hole 14. However, when the aperture ratio of the through hole 14 is increased, the substantial electrical resistance of the surface electrode 3 increases. Therefore, the aperture ratio of the through hole 14 is, for example, 20 to 80%, preferably 30 to 70%, and more preferably 40 to 60%.
[0020]
  The surface electrode 3 shown in FIG. 8 has a through hole 14 as a slit. The slit efficiently transmits light that vibrates in a specific direction. Therefore, the light emitting diode provided with the slit through hole 14 in the surface electrode 3 can emit polarized light. Also in this figure, the surface electrode 3 is represented by cross hatching in order to make the through hole 14 easy to understand.
[0021]
  The slit-shaped through hole 14 has a slit width (H) of λ / 10 or more, preferably λ / 5 or more, more preferably λ / 2 of the peak wavelength λ of the light emitting wavelength of the light emitting chip. If the slit width is smaller than λ / 10, the light emitted from the light emitting chip cannot be transmitted. The through hole 14 makes the length (W) of the slit larger than the slit width (H), and efficiently transmits polarized light. The length (W) of the slit is larger than λ / 2 of the peak wavelength λ of the wavelength of the light emitting chip, and preferably larger than λ, in order to efficiently transmit light emitted from the light emitting chip.
[0022]
  As shown in FIG. 4, a light emitting diode having a through hole 14 in the surface electrode 3 is provided with a dielectric antenna in the through hole 14 or without providing an antenna as shown in FIG. Permeate.However, the structure of the derivative antenna shown in FIG. 4 does not show an embodiment of the present invention.The light emitting diode provided with the dielectric antenna 2 and the light emitting diode without the dielectric antenna emit light to the outside through the through hole 14 while reflecting light by the inner surface of the surface electrode 3 and the light reflecting layer 6.
[0023]
  Further, the light emitting chip 1 of the light emitting diode shown in FIGS. 3 and 4 is provided with a light reflecting layer 6 at a position facing the surface electrode 3. The light reflecting layer 6 can be formed by providing a metal electrode or a non-electrode metal layer on the back surface semiconductor layer 5 of the light emitting chip 1. In the light emitting chip 1 shown in FIG. 3, a back electrode 8 is provided on the lower surface of the back semiconductor layer 5 to form a light reflecting layer 6. In the light reflection layer 6, the surface of the back electrode 8 is a light reflection surface 6A. Furthermore, the light-emitting chip 1 shown in FIG. 4 is provided with a light reflecting layer 6 by disposing a metal thin film on the back semiconductor layer 5 of the light-emitting chip 1. The metal thin film that is the light reflecting layer 6 is laminated between the back semiconductor layer 5 and the substrate 13. The light reflection layer 6 also has a surface that is a boundary surface with the back semiconductor layer 5 as a light reflection surface 6A. Further, in the light emitting diode, a light emitting chip can be fixed to a holder, and a light reflecting layer can be provided on the holder.
[0024]
  The light reflecting layer 6 has a light reflecting surface 6A as an uneven surface. In particular, the light-emitting diode having the through hole 14 as a slit has the light reflecting surface 6A as an uneven surface. This is because light is reflected to change the polarization direction into various directions. In the light emitting diode in which the through-hole 14 is circular or polygonal and transmits light without being polarized, the light reflecting surface 6A of the light reflecting layer 6 can be a smooth surface.
[0025]
  As shown in FIGS. 3 and 4, the light reflecting layer 6 reflects light irradiated downward from the light emitting chip 1 on the light reflecting surface 6 </ b> A as indicated by arrows in the drawing. The reflected light passes through the through hole 14 and is emitted to the outside of the light emitting chip 1. Light that does not pass through the through hole 14 is repeatedly reflected by the surface electrode 3 and the light reflecting layer 6A, and is irradiated to the outside from the through hole 14. The light emitting diode in which the dielectric antenna 2 is provided in the through hole 14 collects light near the through hole 14 and transmits the light through the through hole 14. For this reason, light can be transmitted to the surface electrode 3 more efficiently by substantially the same action as increasing the through hole 14.
[0026]
  The light reflecting layer is not necessarily made of a metal thin foil, and may be a multilayer light reflecting layer in which materials having different dielectric constants are alternately laminated. This multilayer light reflecting layer is formed, for example, by alternately laminating AlGaN and GaN. Since the light reflecting layer which is a multilayer light reflecting layer can reflect light with high reflectivity, light leakage to the substrate side can be reduced.
[0027]
  Furthermore, the light emitting chip 1 of the light emitting diode shown in FIG. 9 includes a phosphor layer 9 between the light reflecting layer 6 and the back surface semiconductor layer 5. In the light emitting chip 1 shown in this figure, a substrate 13 is laminated on the lower surface of the back surface semiconductor layer 5, and a light reflecting layer 6 is laminated on the lower surface of the substrate 13 via a phosphor 9. The phosphor layer 9 contains a phosphor that converts the wavelength of light emitted from the light emitting chip 1. The light emitting diode transmits light emitted from the light emitting chip 1 from the dielectric antenna 2 to the outside while converting the wavelength of the phosphor layer 9. In particular, this light-emitting diode has a feature that the reflected light reflected by the lower surface of the surface electrode 3 and the reflecting surface 6A of the light reflecting layer 6 repeatedly passes through the phosphor layer 9, so that it can be irradiated to the outside while efficiently converting the wavelength. There is. The phosphor layer 9 can contain, for example, a phosphor that converts the wavelength of blue light emission into red or yellow.
[0028]
  By providing the dielectric antenna 2, the through hole 14 of the surface electrode 3 can reduce the aperture ratio and increase the light transmittance. Dielectric antenna 2 is provided connected to through hole 14. The dielectric antenna 2 has a height (T) 0.5 to 5 times the maximum peak wavelength λmax of the light-emitting chip 1, a minimum width (D) 0.5 to 2 times the height (T), and The interval (L) between adjacent dielectric antennas 2 is set to 0.5 to 10 times the maximum peak wavelength λmax. Further, preferably, the interval (L) between adjacent dielectric antennas 2 is 0.5 to 10 times the height (T) of the dielectric antenna.
[0029]
  It is an electromagnetic wave that makes the height (T) of the dielectric antenna 2 0.5 to 5 times the maximum peak wavelength λmax, whether it is too short or too long compared to the maximum peak wavelength λmax. This is because the sensitivity to receive light decreases. Moreover, if the minimum width (D) of the dielectric antenna 2 is too narrow or too wide, the reception sensitivity of light that is an electromagnetic wave is lowered, and the interval (L) between adjacent dielectric antennas 2 is too narrow. However, even if it is too wide, the reception sensitivity is lowered. The dielectric antenna 2 provided on the light-emitting chip 1 having a maximum peak wavelength λmax of about 0.5 μm has a height of the dielectric antenna 2 when the height (T) is 0.5 to 5 times the maximum peak wavelength λmax. (T) is 0.25 to 2.5 μm.
[0030]
  The dielectric antenna 2 may be a polygonal column as shown in FIG. 10, a cylindrical shape as shown in FIG. 11, or an elliptical column shape (not shown). However, FIG. 10 and FIG. 11 do not relate to the embodiment of the present invention, but are described as reference examples. Furthermore, as shown in FIGS. 12 and 13, the dielectric antenna 2 can also have a prismatic shape with a planar shape that is an elongated rectangle. Moreover, as shown in FIG. 14, it can also be set as the elongate columnar shape which makes circular arc shape at both ends in planar shape. However, these drawings show a state in which the surface electrode 3 disposed between the dielectric antennas 2 is removed in order to make the shape of the dielectric antenna 2 easy to understand. Actually, the dielectric antenna 2 is, tableA surface electrode 3 is provided. Furthermore, although the dielectric antenna 2 in the above figures has a flat tip, the dielectric antenna 2 can also have a curved surface, although not shown.
[0031]
  The dielectric antenna 2 is made of an inorganic or organic dielectric. A material having a dielectric constant of 1.1 to 10 is suitable for the dielectric. Furthermore, the ratio (ε1 / ε2) of the dielectric constant (ε1) of the dielectric forming the dielectric antenna 2 and the dielectric constant (ε2) of the surface semiconductor layer 4 can be 1.1-10. Glass, SiO as inorganic dielectric₂, Al₂O_ThreeEtc. can be used. As the organic dielectric, polypropylene, polyethylene, fluorine resin, or the like can be used.
[0032]
  The dielectric antenna 2 can be formed by etching the surface of the light emitting chip 1 and filling the etched portion with a dielectric. FIG. 15 shows a process of providing the dielectric antenna 2 on the light emitting chip 1.However, the structure of the derivative antenna shown in FIG. 15 does not show an embodiment of the present invention.A light-emitting chip 1 shown in FIG. 15A is provided with a surface electrode 3 in ohmic contact with the surface semiconductor layer 4. The light emitting chip 1 is a light emitting diode chip that emits light when a voltage is applied to both sides thereof, and is a pn junction semiconductor. The pn junction of the light emitting chip 1 does not necessarily have a layer structure in which one p layer and one n layer are stacked. The p layer and the n layer may have a plurality of layer configurations. The light emitting chip 1 has a pn junction semiconductor and a layer structure specified by the light emission color of the light emitting diode. For example, a light emitting chip of a gallium nitride compound semiconductor layer is used for a blue light emitting, green light emitting, or white light emitting diode.
[0033]
  In the light emitting chip 1, as shown in FIG. 15B, the surface electrode 3 and the surface semiconductor layer 4 are etched to provide a recess 7 in which the dielectric antenna 2 is provided. The light-emitting chip 1 shown in the drawing opens a through hole 14 penetrating the surface electrode 3 by etching, and a recess 7 is formed by cutting out a surface portion of the surface electrode layer 4 facing the through hole 14. Thereafter, as shown in FIG. 15 (3), the dielectric antenna 2 is provided by filling the through hole 14 and the recess 7 formed by etching with a dielectric.
[0034]
  In the light-emitting chip 1 of FIG. 15, the tip surface of the dielectric antenna 2 and the surface of the surface electrode 3 are substantially flush with the surface of the light-emitting chip 1 being a smooth surface. However, the front end surface of the dielectric antenna and the surface of the surface electrode do not necessarily need to be the same plane, and may be a rough surface with some unevenness. The front end surface of the dielectric antenna can be made somewhat lower than the surface of the surface electrode, or conversely, it can be made to protrude from the surface of the surface electrode. A light emitting chip in which the tip surface of the dielectric antenna is formed to be lower than the surface of the surface electrode is manufactured by adjusting the amount of the dielectric filled in the through hole 14 of the surface electrode 3 as shown in FIG. TheHowever, the structure of the derivative antenna shown in this figure does not show an embodiment of the present invention.
[0035]
  A light emitting chip in which the front end surface of the dielectric antenna projects from the surface of the surface electrode is manufactured by the process shown in FIG. The light emitting chip 1 shown in (1) of FIG. 17 is provided with a surface electrode 3 in ohmic contact with the surface semiconductor layer 4. In this light emitting chip 1, as shown in FIG. 17 (2), the surface electrode 3 and the surface semiconductor layer 4 are etched to provide a through hole 14 and a recess 7 in which the dielectric antenna 2 is provided. Next, as shown in FIG. 17 (3), a dielectric film 12 is laminated on the surface of the surface electrode 3 and the surface electrode layer 4. Thereafter, as shown in FIG. 17 (4), the dielectric film 12 provided on the upper surface of the surface electrode 3 is removed by etching, and the dielectric antenna 2 protruding from the surface electrode 3 is formed. The amount of protrusion of the dielectric antenna 2 from the surface electrode 3 can be adjusted by the thickness of the dielectric film 12.
[0036]
  As shown in FIG. 18, the light emitting chip formed by projecting the front end surface of the dielectric antenna from the surface of the surface electrode can be provided with the dielectric antenna 2 by etching only the surface electrode 3. However, this figure does not show an embodiment of the present invention. In the light emitting chip 1, the surface electrode 3 is provided in ohmic contact with the surface semiconductor layer 4, and then the surface electrode 3 is etched to provide the through hole 14. Next, a dielectric film 12 is laminated on the surface of the surface electrode 3 and the surface electrode layer 4. Thereafter, the dielectric film 12 provided on the upper surface of the surface electrode 3 is removed by etching, and the dielectric antenna 2 protruding from the surface electrode 3 is formed. However, in the step of forming the surface electrode, the through hole 14 can be formed in the surface electrode by a lift-off method.
[0037]
  In the above light emitting chip, the dielectric antenna 2 is provided through the through hole 14 of the surface electrode 3 or inside the through hole 14. However, as shown in FIG. 9, the light-emitting chip 1 is a position facing the through hole 14 opened in the surface electrode 3, and is a dielectric antenna from the surface of the surface semiconductor layer 4 of the light-emitting chip 1 toward the inside. 2 can also be provided. However, FIG.The structure of the derivative antenna shown inIt is not related to the embodiment of the present invention, but is described as a reference example.NoThe The light emitting diode collects light emitted from the light emitting chip 1 by the dielectric antenna 2 and transmits the light through the through hole 14 of the surface electrode 3 to the surface side of the surface electrode 3.
[0038]
  The light emitting chip 1 shown in FIG. 9 can be provided with the dielectric antenna 2 in the step shown in FIG. In this light emitting chip 1, as shown in FIG. 19 (2), the surface semiconductor layer 4 is etched to remove the region where the dielectric antenna 2 is provided and provide the recess 7. After that, as shown in FIG. 19 (3), the dielectric antenna 2 is formed by filling the recesses 7 of the etched surface electrode layer 4 with a dielectric. Next, as shown in (4) of FIG. 19, the surface electrode 3 is formed between the dielectric antennas 2 by the lift-off method. At this time, the surface electrode 3 is formed in a state where the through hole 14 is opened in the dielectric antenna 2.
[0039]
  Further, in the light emitting chip 1 shown in FIG. 9, the dielectric antenna 2 can be provided at a position facing the through hole 14 of the surface electrode 3 in the step shown in FIG. In the light emitting chip 1, as shown in FIG. 20 (2), the surface electrode 3 is etched to open a through hole 14 penetrating the surface electrode 3. At this time, the surface portion of the surface electrode layer 4 is not etched. However, the through hole 14 of the surface electrode can also be formed by a lift-off method. Further, ions are implanted into the through-holes 14 of the surface electrode 3 to form the dielectric antenna 2 by partially increasing the dielectric constant of the surface semiconductor layer 4 as shown in FIG. As ions implanted into the through holes 14, ions of arsenic, gallium, aluminum and the like can be used. The ions implanted from the through holes 14 alter the semiconductor that is the surface semiconductor layer 4 to increase the dielectric constant.
[0040]
  Further, in the step shown in FIG. 19 or FIG. 20, the light emitting chip protrudes from the through hole 14 opened in the surface electrode 3 after providing the dielectric antenna 2 from the surface of the surface semiconductor layer 4 to the inside. The dielectric antenna 2 can also be formed. As shown in FIG. 21, the light-emitting chip includes a dielectric antenna 2 formed on the surface of the surface semiconductor layer 4 and a dielectric film 12 laminated on the surface of the surface electrode 3. The dielectric film 12 provided on the upper surface is removed by etching, and the dielectric antenna 2 protruding from the surface electrode 3 is formed. This dielectric antenna preferably has a higher dielectric constant of the dielectric antenna 2 formed protruding from the through hole 14 than the dielectric constant of the dielectric antenna 2 formed on the surface semiconductor layer 4 in the previous step. .
[0041]
  Through the above steps, the surface electrode 3 is disposed between the dielectric antennas 2 in the light emitting chip 1. The dielectric antenna 2 is provided at a position facing the through hole 14 of the surface electrode 3. The dielectric antenna 2 provided in the light emitting chip 1 with this structure collects the light incident on the periphery thereof and transmits it to the surface side of the surface electrode 3. Since the dielectric antenna 2 collects ambient light, even if the surface electrode 3 that does not transmit light is provided between the dielectric antennas 2, the light transmittance is not lowered by the surface electrode 3.
[0042]
  Furthermore, in the light emitting diode of the present invention, the dielectric antenna 2 can be formed of a multilayer dielectric film 10 as shown in FIG.However, the structure of the derivative antenna shown in this figure does not show an embodiment of the present invention.The dielectric antenna 2 having this structure can suppress transmission of light having a predetermined wavelength by specifying the material, thickness, and number of layers of the dielectric film 10. For example, the dielectric antenna 2 can increase the blue reflectance by adjusting the material, thickness, and number of layers of the dielectric film 10 so as to suppress the intensity of blue transmitted light. Further, the light emitting diode shown in this figure is reflected by the dielectric film 10 because the phosphor layer 9 is provided between the light reflecting layer 6 and the back surface semiconductor layer 5 in the same manner as the light emitting diode shown in FIG. The blue light emission can be wavelength-converted into red or yellow more efficiently by the phosphor layer 9.
[0043]
  Furthermore, the light emitting diode shown in FIG. 23 includes a nonlinear optical material layer 11 between the light reflecting layer 6 and the back surface semiconductor layer 5.However, the structure of the derivative antenna shown in this figure does not show an embodiment of the present invention.In the light-emitting chip 1 shown in this figure, a glass substrate 13 is laminated on the lower surface of the back surface semiconductor layer 5, and a light reflecting layer 6 is laminated on the lower surface of the glass substrate 13 via a nonlinear optical material layer 11. The nonlinear optical material layer 11 converts the wavelength and frequency of light by a nonlinear optical effect. The nonlinear optical material layer 11 can extract light having a shorter wavelength by converting the frequency of light passing therethrough to high frequency. In particular, this light emitting diode has a feature that the frequency conversion can be efficiently performed because the reflected light reflected by the lower surface of the surface electrode 3 and the light reflecting surface 6A of the light reflecting layer 6 repeatedly passes through the nonlinear optical material layer 11. For the nonlinear optical material layer 11, for example, ADP, KDP, BBO or the like can be used.
[0044]
【The invention's effect】
  The light emitting diode of the present invention has an excellent feature that the supply voltage of the light emitting diode can be lowered while efficiently taking out the light emitted from the light emitting chip. The light emitting diode according to the present invention has a surface electrode which is a metal electrode layer on the first surface side of the light emitting chip, and a light reflecting layer on the second surface side opposite to the light emitting chip. This is because the through hole is provided so that the light from the light emitting chip is transmitted from the through hole to the surface side of the surface electrode while being reflected by the light reflecting layer. This light emitting diode emits light reflected by the inner surface of the surface electrode and the light reflecting layer to the outside from the through hole. Therefore, even if the surface electrode is a non-transparent metal electrode layer, the light from the light emitting chip is directed to the surface side. It can be transmitted. For this reason, the light emission of the light emitting chip can be efficiently extracted outside without using an expensive transparent electrode having a high specific resistance and a large internal resistance. Therefore, the light emitting diode of the present invention can reduce the electrical resistance of the surface electrode and emit light from the light emitting chip with a low supply voltage, and can reduce the manufacturing cost of the light emitting diode and can be mass-produced at low cost.
[0045]
  Furthermore, the light-emitting diode of the present invention has an advantage that polarized light can be efficiently emitted. The light-emitting diode has a plurality of through-holes provided in the surface electrode as slits, and the light reflecting surface of the light reflecting layer has an uneven surface, while reflecting light from the light emitting chip by the light reflecting layer. This is because the light is polarized from the through hole and transmitted to the surface side of the surface electrode. In particular, since the light emitting diode of the present invention is provided with a dielectric antenna in the through hole of the slit, polarized light can be emitted more efficiently.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing an electrode structure of a conventional light emitting diode
FIG. 2 is a schematic sectional view showing an electrode structure of another conventional light emitting diode.
FIG. 3 of the present inventionReference examplePartially enlarged sectional view showing the electrode structure of a light emitting diode
FIG. 4 shows another embodiment of the present invention.Reference examplePartially enlarged sectional view showing the electrode structure of a light emitting diode
FIG. 5 is a plan view showing an example of a through hole of a surface electrode
FIG. 6 is a plan view showing another example of the through hole of the surface electrode
FIG. 7 is a plan view showing another example of the through hole of the surface electrode
FIG. 8 is a plan view showing another example of the through hole of the surface electrode
FIG. 9 shows another embodiment of the present invention.Reference exampleSectional view showing the electrode structure of a light emitting diode
FIG. 10 is an enlarged cross-sectional perspective view showing an example of a dielectric antenna.
FIG. 11 is an enlarged cross-sectional perspective view showing another example of a dielectric antenna.
FIG. 12 is an enlarged cross-sectional perspective view showing another example of a dielectric antenna.
FIG. 13 is an enlarged cross-sectional perspective view showing another example of a dielectric antenna.
FIG. 14 is an enlarged cross-sectional perspective view showing another example of a dielectric antenna.
FIG. 15 is a cross-sectional view showing a process of providing a dielectric antenna in a through hole of a surface electrode
FIG. 16 is a cross-sectional view showing another example of the step of providing a dielectric antenna in the through hole of the surface electrode
FIG. 17 is a cross-sectional view showing another example of the step of providing a dielectric antenna in the through hole of the surface electrode
FIG. 18 is a cross-sectional view showing another example of the step of providing a dielectric antenna in the through hole of the surface electrode
FIG. 19 is a cross-sectional view showing another example of the step of providing a dielectric antenna in the through hole of the surface electrode
FIG. 20 is a cross-sectional view showing another example of the step of providing a dielectric antenna in the through hole of the surface electrode
FIG. 21 is a sectional view showing another example of the step of providing a dielectric antenna in the through hole of the surface electrode.
FIG. 22 shows another embodiment of the present invention.Reference examplePartially enlarged sectional view showing the electrode structure of a light emitting diode
FIG. 23 shows another embodiment of the present invention.Reference exampleSectional view showing the electrode structure of a light emitting diode
[Explanation of symbols]
    1 ... Light emitting chip
    2. Dielectric antenna
    3 ... Surface electrode
    4 ... Surface electrode layer
    5 ... Backside semiconductor layer
    6 ... Light reflecting layer 6A ... Light reflecting surface
    7 ... recess
    8 ... Back electrode
    9 ... phosphor layer
  10. Dielectric film
  11 ... Nonlinear optical material layer
  12 ... Dielectric film
  13 ... Board
  14 ... through hole
  20 ... Light emitting chip
  21 ... Electrode 21A ... Transparent electrode
                          21B: Bonding

Claims (15)

A light emitting chip (1) having a surface electrode (3) on the first surface side, and a second surface side on the opposite surface opposite to the first surface side of the light emitting chip (1). A light-emitting diode having a light reflecting layer (6),
The surface electrode (3) is a metal electrode layer that reflects light on the inner surface, and the surface electrode (3) is provided with a plurality of through holes (14) that can transmit light, and the through holes serve as slits.
The length (W) of the slit is larger than the slit width (H) and larger than λ / 2 of the peak wavelength λ of the light emitting wavelength of the light emitting chip (1),
Furthermore, the through hole (14) is provided with a dielectric antenna (2),
The dielectric antenna (2) is provided so as to protrude from the surface electrode (3) provided on the surface of the surface semiconductor layer (4) of the light-emitting chip (1), and the dielectric antenna (2) , Provided to protrude from the surface of the surface semiconductor layer (4) of the light emitting chip (1) toward the inside,
The dielectric antenna (2) is columnar, and the dielectric constant of the dielectric forming the dielectric antenna (2) is 1.1 to 10,
The height (T) of the dielectric antenna (2) is 0.5 to 5 times the maximum peak wavelength λmax of the light emitting chip (1), and the minimum width (D) is 0.5 to 2 times the height. A light emitting diode in which the distance (L) between adjacent dielectric antennas (2) is 0.5 to 10 times the maximum peak wavelength λmax.   The light reflecting layer (6) has a light reflecting surface (6A) as an uneven surface, and the light from the light emitting chip (1) is reflected from the light reflecting layer (6) while being polarized from the through hole (14) of the slit to be surface electrode ( The light-emitting diode according to claim 1, wherein the light-emitting diode is transmitted through the surface side of 3).   The light-emitting diode according to claim 1, wherein the through hole (14) of the surface electrode (3) is a slit, and the length (W) of the slit is larger than twice the slit width (H).   The light emitting diode according to claim 2, wherein the light emitting chip (1) is fixed to a holder, and the light reflecting layer (6) is provided on the holder.   The light emitting diode according to claim 2, wherein a light reflecting layer (6) is laminated and fixed on the second surface side of the light emitting chip (1).   The light emitting diode according to claim 1, wherein the aperture ratio of the surface electrode (3) is 20 to 80%.   The light emitting diode according to claim 1, wherein the aperture ratio of the surface electrode (3) is 30 to 70%.   The light emitting diode according to claim 1, wherein the aperture ratio of the surface electrode (3) is 40 to 60%.   The light emitting diode according to claim 1, further comprising a phosphor layer (9) between the light emitting chip (1) and the light reflecting layer (6). The light emitting diode according to claim 9 , wherein the phosphor layer (9) converts the wavelength of blue light emission into red or yellow.   The light emitting diode according to claim 1, further comprising a nonlinear optical material layer (11) between the light emitting chip (1) and the light reflecting layer (6).   The light emitting diode according to claim 1, wherein the light emitting chip (1) is a light emitting chip formed by laminating gallium nitride compound semiconductor layers.   The light emitting diode according to claim 1, wherein the height (T) of the dielectric antenna (2) is 0.5 to 5 µm.   The light-emitting diode according to claim 1, wherein the dielectric antenna (2) has a prismatic shape having a planar shape that is an elongated rectangle, or a columnar shape having an elongated shape having arcuate ends at the planar shape.   The light-emitting diode according to claim 1, wherein the dielectric antenna (2) is formed of a multilayer dielectric film (10).

Images