JP6501200B2 - Light emitting element - Google Patents

Description

  The present invention relates to a light emitting device made of a group III nitride semiconductor. In particular, the present invention relates to a light emitting device having a structure suitable for optical communication applications, which is characterized by a light emitting region and a planar pattern of an electrode.

  In short distance optical fiber communication, POF (plastic optical fiber) is widely adopted for reasons such as low cost and bending resistance. Since POF has a low loss in the green band, a green light emitting element composed of a group III nitride semiconductor is suitable as a light source.

  In such communication applications, it is desirable to reduce the light output drop at high currents. This is because the maximum current value required to obtain the desired contrast can be reduced. In order to suppress the decrease in light output at high current, it is effective to achieve uniform light emission.

  Patent Document 1 describes a light emitting element in which a flat pattern of a light emitting layer is a circle, and an n electrode of a circular flat pattern above the light emitting layer and a p electrode of a ring flat pattern surrounding the light emitting layer are provided. . The planar pattern of the light emitting region is a circle similar to the planar pattern of the light emitting layer. Also, it is described that a current blocking layer is provided on the top of the light emitting layer to limit a region through which current flows. By configuring the planar pattern of the light emitting element in this manner, it is described that the current flowing to the light emitting layer becomes uniform.

  In Patent Document 2, a central portion is etched in a circular shape to expose an n layer, a circular n electrode in the central portion, a p electrode in a ring-like plane pattern surrounding it, and a light emitting region as the p electrode And a ring-shaped light emitting element is described. It is described that the light emission is made uniform by this.

JP, 2009-146980, A JP, 2013-145913, A

  However, in the conventional light emitting element, the light emission is not sufficiently uniform, and the suppression of the decrease in light output at a high current is not sufficient. In addition, it was difficult to emit light uniformly as compared with blue light emission in green light emission. Therefore, it has been desired to make the light emission more uniform.

  Therefore, an object of the present invention is to achieve uniform light emission and to suppress a decrease in light output at high current.

A first aspect of the present invention is a light emitting element comprising a group III nitride semiconductor, having a plurality of first element regions for emitting light, wherein a p electrode and an n electrode are provided in each first element region. The plane pattern of each light emitting area of the first element area is a circumference or an arc, and the plane pattern as the whole light emitting area is set to be a concentric circle or a concentric arc, and one of p electrode and n electrode The plane pattern is a circle, a sector, a circle or an arc which is provided opposite to the inside of the plane pattern of the circumference or arc of the light emitting area and has the same center and central angle as the circumference or arc, p the other planar pattern of electrodes and n electrodes are provided opposite to the outside of the arc of the planar pattern of the light emitting region, Ri circumferential or arc der to its circumference or arc and center and center angle equal, each First element area It is connected in parallel to a light emitting element, characterized in that.

Another invention different from the present invention is a light emitting element comprising a group III nitride semiconductor, having one first element region for emitting light, and a p electrode and an n electrode provided in the first element region, wherein the first element The plane pattern of the light emitting area of the area is a circle or an arc, and the plane pattern of one of the p electrode and the n electrode is provided opposite to the inside of the plane pattern of the circle or arc of the light emitting area Or a circle, a sector, a circle, or an arc having the same center and center angle as the arc, and the other plane pattern of the p electrode and the n electrode is provided opposite to the plane pattern of the arc of the light emitting region , A circumference or arc having the same center and center angle as the circumference or arc, electrically isolated from the first element area outside the first element area, and provided with ap electrode and an n electrode No light and no light A light emitting element having a two-element region.

  In the first aspect of the present invention, similarly to the second aspect, the first element region is electrically separated from the first element region outside the first element region, and the p electrode and the n electrode are not provided, and light emission is obtained. You may make it have a 2nd element area | region which does not have. By absorbing the light on the short wavelength side of the peak wavelength of light emission by the second element region, the half width of the light emission spectrum becomes narrower and the directivity becomes higher. Therefore, light emission becomes more suitable for short distance optical communication using POF.

  In the first aspect of the present invention, the area S of the plane pattern of each light emitting area is 0.9 × S 0 or more and 1.1 × S 0 or less, where S 0 is the average value of the areas of the plane patterns of each light emitting area. It should be a range. The light emission from each of the light emitting regions 101a to 101d is more uniform. More preferably, it is in the range of 0.95 × S 0 or more and 1.05 × S 0 or less, and the most desirable is to equalize the area of the planar pattern of each light emitting region.

  Further, in the first aspect of the present invention, each element region may be connected in parallel. The response speed can be improved, and it can be more suitable for optical communication.

  In the present invention, the width of the circumference or arc of the light emitting region may be 5 to 20 μm. More uniform light emission can be achieved. More desirably, it is 5-15 micrometers, More preferably, it is 5-10 micrometers.

  The present invention is particularly effective for green light emitting devices. This is because it was difficult to cause the device emitting green light to emit light uniformly as compared to the device emitting blue light. The green emission has a center wavelength in the range of 490 to 570 nm. A more desirable range of emission wavelength is 500 to 530 nm.

  The light emitting device of the present invention is particularly effective as a light source application of optical communication using POF (plastic optical fiber). The light emitting element of the present invention suppresses the decrease in light output at high current, and can reduce the maximum current value required to obtain a desired contrast.

  According to the present invention, light can be emitted uniformly from the light emitting region, and a decrease in light output at high current can be suppressed.

FIG. 2 is a plan view showing the configuration of a light emitting element of Example 1; FIG. 2 is a cross-sectional view showing the configuration of a light emitting element of Example 1; FIG. 2 is a cross-sectional view showing the configuration of a light emitting element of Example 1; FIG. 7 is a cross-sectional view showing a modified example of the configuration of the light emitting device of Example 1; FIG. 7 is a plan view showing the configuration of a light emitting element of Example 2; FIG. 7 is a cross-sectional view showing the configuration of a light emitting device of Example 2; FIG. 7 is a cross-sectional view showing a modified example of the configuration of the light emitting device of Example 2; A graph showing the relationship between forward current and light output. FIG. 7 is a plan view showing the configuration of a light emitting device of Example 3;

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the embodiments.

  FIG. 1 is a plan view showing the configuration of the light emitting device of Example 1. FIG. FIG. 2 is a cross-sectional view showing the configuration of the light emitting device of Example 1. As shown in FIG. The cross sectional view of FIG. 2 is a cross section taken along line A-A 'in FIG. The cross sectional view of FIG. 3 is a cross section taken along line B-B 'in FIG. The light-emitting element of Example 1 is a face-up type, and has a structure in which light is extracted from the back side to the front side in the direction perpendicular to the paper surface in FIG. Moreover, the light emitting element of Example 1 is green light emission (central wavelength of 490 to 570 nm) suitable for short distance optical communication using POF.

  As shown in FIG. 2, the light emitting device of Example 1 has a substrate 10, and an n layer 11 made of a group III nitride semiconductor, a light emitting layer 12, and a p layer 13 are stacked on the substrate 10. The current blocking layer 14 is provided in a predetermined region, the transparent electrode 15 is provided on the p layer 13 and the current blocking layer 14, the p electrode 16 on the transparent electrode 15 and the n electrode 17 on the n layer 11 exposed by the groove. It is the structure provided. Details of the configuration of each layer will be described later.

  Next, with reference to FIG. 1, the planar pattern of the light emitting element of Example 1 will be described.

  As shown in FIG. 1, the light emitting element of Example 1 is a square having a side of 420 μm in plan view, and the element separation groove 19 electrically connects four first element regions 100 a to 100 d and a second element region 100 e. Are separated. Here, the element region is a region where the laminated structure of the n layer 11, the light emitting layer 12 and the p layer 13 is formed on the substrate 10 (however, the region where the n electrode 17 is formed is up to the n layer 11). The element separation groove 19 is a groove having a depth reaching the substrate 10 from the surface of the p layer 13. The depth of the element isolation groove 19 may be a depth at which the light emitting layer 12 is electrically isolated, and may be a depth reaching the n layer 11 from the surface of the p layer 13. The four first element regions 100a to 100d are connected in parallel by the p electrode 16 and the n electrode 17, and have light emitting regions 101a to 101d for emitting light. On the other hand, the second element region 100 e is not provided with the p electrode 16 and the n electrode 17 and does not emit light.

  The plane pattern of the first element regions 100a and 100b and the plane pattern of the first element regions 100c and 100d are symmetrical patterns with respect to the central axis parallel to the sides of the square in the square plane pattern of the light emitting element.

  The plane pattern of the first element regions 100a and 100c is a circle as shown in FIG. 1, and the radius of each is equal. The center O1 of the circle of the plane pattern of the first element region 100a is located at the center near one side 102a in the square plane pattern of the light emitting element. The center O2 of the circle of the plane pattern of the first element region 100c is located at the center in the vicinity of the side 102b which is the opposite side of the side 102a in the square plane pattern of the light emitting element.

  The plane pattern of the first element regions 100b and 100d is an arc as shown in FIG. 1, and the radius of each and the width of the arc are equal. The center of a circular arc which is a plane pattern of the first element region 100b is the same as the center O1 of a circle which is a plane pattern of the first element region 100a. Further, the radius of the arc that is the plane pattern of the first element region 100b is larger than the radius of the circle that is the plane pattern of the first element region 100a, and the circle is included. The center of the circular arc which is a plane pattern of the first element region 100d is the same as the center O2 of the circle which is a plane pattern of the first element region 100c. Further, the radius of the arc that is the plane pattern of the first element region 100d is larger than the radius of the circle that is the plane pattern of the first element region 100c, and the circle is included.

  The second element region 100e is a region which is separated by the element isolation groove 19 outside the first element regions 100b and 100d (opposite to the central portion side of the arc which is the plane pattern thereof). The p electrode 16 and the n electrode 17 are not connected to the second element region 100e, and are electrically separated from the first element regions 100a to 100d. Therefore, the second element region 100e is a region which does not emit light. The second element region 100 e is a region where the n layer 11, the light emitting layer 12 and the p layer 13 may be removed to form an element isolation trench 19, but it is desirable to leave it as in the first embodiment. This is because the second element region 100 e is made to function as an absorption layer that absorbs light on the short wavelength side of the peak wavelength among the light emitted from the light emitting regions 101 a to 101 d. By this function, the half width of the emission spectrum becomes narrower and the directivity becomes higher. Therefore, light emission becomes more suitable for short distance optical communication using POF.

  The planar patterns of the light emitting regions 101a and 101c are circumferential (circular ring shape) included in the first element regions 100a and 100c, respectively. The center of the circumference which is a plane pattern of light emission field 101a is the same as center O1 of the circle which is a plane pattern of the 1st element field 100a. The center of the circumference which is a plane pattern of light emission field 101c is the same as center O2 of the circle which is a plane pattern of the 1st element field 100c.

  The planar patterns of the light emitting regions 101b and 101d are arc shapes (semicircular ring shapes) having a central angle of 180 ° included in the first element regions 100b and 100d, respectively. The direction connecting the two ends of the arc is parallel to the sides 102a and 102b. The center of the arc which is a plane pattern of the light emitting area 101b is the same as the center O1 of the circle which is a plane pattern of the first element area 100a. Further, the center of the arc that is the plane pattern of the light emitting area 101d is the same as the center O2 of the circle that is the plane pattern of the first element area 100c. In addition, the width of the arc that is the plane pattern of the light emitting areas 101b and 101d is the same as the width of the circumference that is the plane pattern of the light emitting areas 101a and 101c. In addition, the radius of the arc (the distance from the center to the center of the width of the arc in the radial direction) which is the plane pattern of the light emitting areas 101b and d is twice the radius of the circle which is the plane pattern of the light emitting areas 101a and 101c. . Therefore, the areas of the planar patterns of the light emitting regions 101a to 101d are equal to one another.

  The plane pattern of each of the light emitting regions 101a to 101d is not limited to the above, and may be any pattern as long as it is a circumference or a circular arc. In addition, it is preferable to arrange the light emitting regions 101a to 101d concentrically around a certain point and to arrange them symmetrically with respect to the planar pattern of the element.

  Moreover, in Example 1, although the area of the plane pattern of each light emission area | region 101 ad is made equal, respectively, you may differ. However, in order to obtain uniform light emission, the area S of the plane pattern of each of the light emitting areas 101a to 101d is 0.9 × S0 or more, where the average value of the areas of the plane patterns of each of the light emitting areas 101a to 101d is S0. It is preferable that the range be 1 × S 0 or less. More preferably, it is in the range of 0.95 × S 0 or more and 1.05 × S 0 or less, and it is most desirable to equalize the area of the planar pattern of each of the light emitting regions 101 a to 101 d as in the first embodiment.

  In addition, it is preferable that the entire area of the light emitting regions 101a to 101d be 1 to 30% of the area of the planar pattern of the entire light emitting element. The response speed can be improved by the reduction of the light emitting area, and it can be made suitable for optical communication. More desirably, it is 1 to 20%, and further desirably, 1 to 10%.

  The width of each of the light emitting regions 101a to 101d is preferably 5 to 20 μm. Further uniform emission can be achieved. More desirably, it is 5-15 micrometers, More preferably, it is 5-10 micrometers.

  The planar patterns of the first element regions 100a to 100d are not limited to those in the first embodiment as long as they are patterns electrically separated from each other, but for the purpose of uniform light emission, the planar pattern of the light emitting region 101a It should be similar to

  The plane pattern of the p electrode 16 is formed by connecting circumferential portions 16a and 16c, which are circumferential plane patterns, and arc portions 16b and d, which are circular plane patterns having a central angle of 180.degree. It is comprised by the connection part 16e which is a linear planar pattern of a type | mold.

  The plane pattern of the circumferential portion 16a is a ring shape that is outside the light emitting area 101a, which is a circumferential plane pattern, and has the same center and center of the plane pattern of the light emitting area 101a. It is a pattern. In addition, the plane pattern of the circumferential portion 16c is a circumferential shape (ring shape having the same center as the circumference of the plane pattern of the light emitting region 101c, which is inside the light emitting region 101c which is a circumferential flat pattern. It is a pattern of).

  The plane pattern of the arc portion 16b faces the outside of the light emitting area 101b, which is an arc plane pattern, along the arc and has an arc shape (semicircle having the same center and central angle as the arc of the plane pattern of the light emitting area 101b). Ring pattern). In addition, the plane pattern of the arc portion 16d faces the inside of the light emission area 101b which is an arc plane pattern and faces the arc along the arc, and the arc and the central angle of the plane pattern of the light emission area 101b are the same. It is a pattern.

  The planar pattern of the connection portion 16e is a U-shaped pattern that connects the circumferential portions 16a and 16c and the arc portions 16b and d to each other. Specifically, it extends from the circumferential portion 16a along the side 102a toward the side 102c (one of two sides of the square planar pattern of the light emitting element, which are orthogonal to the sides 102a and b), and the arc portion A linear pattern connected to the end of 16b, a linear pattern extending from the circumferential portion 16c to the side 102c along the side 102b, and connected to the end of the arc 16d, and in the vicinity of the side 102c It is a U-shaped pattern composed of a linear pattern extending along the side 102 c and connecting with the linear pattern parallel to the above sides 102 a and b at both ends.

  The plane pattern of the n electrode 17 is a pattern obtained by rotating the plane pattern of the p electrode 16 by 180 °, and is a circular plane pattern of circumferential portions 17a and 17c, which is a circumferential plane pattern, and a central angle of 180 °. The arc portions 17b and 17d are connected to each other, and a connection portion 17e which is a U-shaped linear planar pattern for connecting the arc portions 17b and d.

  The plane pattern of the circumferential portion 17a is a ring shape that is the inside of the light emitting area 101a, which is a circumferential plane pattern, and has the same center and center of the plane pattern of the light emitting area 101a. It is a pattern. In addition, the plane pattern of the circumferential portion 17c is a circumferential shape (ring shape in which the center and the circumference of the plane pattern of the light emitting area 101c are the same outside the light emitting area 101c which is a circumferential plane pattern. It is a pattern of).

  The plane pattern of the arc portion 17b faces the inside of the light emitting area 101b, which is an arc plane pattern, along the arc and has the same arc and center angle as the arc of the plane pattern of the light emitting area 101b (semicircle Ring pattern). Further, the plane pattern of the arc portion 17d faces the outside of the light emitting area 101b, which is an arc plane pattern, along the arc, and has the same arc and center angle as the arc of the plane pattern of the light emitting area 101b. It is a pattern.

  The plane pattern of the connection portion 17e is a U-shaped pattern which connects the circumferential portions 17a and 17c and the arc portions 17b and d to each other. Specifically, it extends from the circumferential portion 17a along the side 102a toward the side 102d (of the sides of the square planar pattern of the light emitting element, the side facing the side 102c), and the end of the arc portion 17b and A linear pattern to be connected, a linear pattern extending from the circumferential portion 17c to the side 102d along the side 102b and connecting to the end of the arc portion 17d, and along the side 102d near the side 102d It is a U-shaped pattern composed of a straight line pattern which is extended and connected to a straight line pattern parallel to the sides 102a and 102b at both ends.

  The planar pattern of the p electrode 16 and the planar pattern of the n electrode 17 partially overlap, but in the cross section, the insulating film 18 is provided between the p electrode 16 and the n electrode 17 to electrically separate them. There is.

  The planar pattern of the p electrode 16 and the n electrode 17 is not limited to the above, and any pattern may be used as long as the following conditions are satisfied. First, one plane pattern of the p electrode 16 and the n electrode 17 is provided opposite to the inside of the plane pattern of the circumference or arc of each of the light emitting areas 101a to 101d, and the circumference or arc and center and center of the circumference A circle or a circle having the same angle (if the plane pattern of the light emitting areas 101a to 101d is a circle) or a sector or an arc (if the plane pattern of the light emitting areas 101a to 101d is an arc) is required. Second, the other planar pattern of the p electrode 16 and the n electrode 17 is provided to face the outside of the planar pattern of the circumference or arc of each of the light emitting regions 101a to 101d, and the circumference or arc and center and center of the circle It is necessary to have a circle whose corner is the same (if the plane pattern of the light emitting areas 101a to 101d is a circle) or an arc (if the plane pattern of the light emitting areas 101a to 101d is an arc). That is, the planar patterns of the p electrode 16 and the n electrode 17 may be concentric patterns facing each other with the light emitting regions 101a to 101d in a circumferential shape or an arc shape and along the circumference or the arc.

  As described above, when the planar patterns of the light emitting regions 101a to 101d, the p electrode 16, and the n electrode 17 are configured, the shortest distance from the p electrode 16 to the n electrode 17 becomes uniform, and the light emitting regions 101a to 101d in the shortest distance direction Since the width of the light emitting region 101a to 100d is also uniform, the current flowing through the light emitting regions 101a to 101d is uniform everywhere. Therefore, the light emitting regions 101a to 101d can be made to emit light extremely uniformly, and a decrease in light output at high current can be suppressed.

  Next, the configuration of each layer of the light emitting device of Example 1 will be described with reference to FIG.

  The substrate 10 is a sapphire substrate whose surface on the n-layer 11 side is roughened (not shown). Concavo-convex processing is provided to improve the light extraction efficiency. As the material of the substrate 10, a substrate of any material capable of crystal growth of a group III nitride semiconductor can be used other than sapphire. For example, SiC, Si, ZnO or the like.

The n layer 11 has a structure in which an n-type contact layer, an n-type ESD layer, and an n-type SL layer are sequentially stacked from the substrate 10 side. The n-type contact layer is a layer in contact with the n-electrode 17. The n-type contact layer is made of n-GaN having a Si concentration of 1 × 10 ¹⁸ / cm ³ or more. It is also possible to reduce the contact resistance of the n electrode 17 by configuring the n-type contact layer with a plurality of layers having different carrier concentrations. The n-type ESD layer is an electrostatic pressure resistant layer for preventing electrostatic breakdown of the device. The n-type ESD layer is a stacked structure of non-doped GaN and Si-doped n-GaN. The n-type SL layer is an n-type superlattice layer having a superlattice structure in which a plurality of units are repeatedly stacked in units of a structure in which InGaN, GaN, and n-GaN are sequentially stacked. The n-type SL layer is a layer for relieving stress applied to the light emitting layer 12.

  The light emitting layer 12 has an MQW structure in which a well layer made of InGaN and a barrier layer made of AlGaN are repeatedly stacked. The In composition ratio of the well layer is adjusted to be green light emission (center wavelength is 490 to 570 nm). A protective layer may be provided between the well layer and the barrier layer to prevent evaporation of In.

The p layer 13 has a structure in which a p-type cladding layer and a p-type contact layer are laminated in order from the light emitting layer 12 side. The p-type cladding layer is a layer for preventing electrons from diffusing toward the p-type contact layer. The p-type cladding layer is a structure in which a p-InGaN layer and a p-AlGaN layer are sequentially stacked a plurality of times, using a structure in which p-InGaN and p-AlGaN are sequentially stacked. The p-type contact layer is a layer provided for the p electrode 16 to make good contact with the p layer 13. The p-type contact layer is made of p-GaN having a Mg concentration of 1 × 10 ¹⁹ to 1 × 10 ²² / cm ³ and a thickness of 100 to 1000 Å.

  The n layer 11, the light emitting layer 12, and the p layer 13 are electrically separated into the first element regions 100 a to 100 d and the second element region 100 e by the element isolation groove 19.

  The configurations of the n layer 11, the light emitting layer 12, and the p layer 13 are not limited to the above-described configurations, and any configuration conventionally used for a light emitting element made of a group III nitride semiconductor may be employed. Can.

The current blocking layer 14 is made of SiO ₂ and provided in a predetermined region on the p layer 13. The thickness of the current blocking layer 14 is 100 nm. By providing the current blocking layer 14, the current in that region is blocked so that the light emitting regions 101a to 101d have the planar pattern shown in FIG. The planar patterns of the light emitting regions 101 a to 101 d do not overlap with the planar pattern of the p electrode 16. It is for suppressing absorption and shielding of light by the p electrode 16 by not making the region immediately below the p electrode 16 shine and by reflecting light directed to the p electrode 16 by reflection by the current blocking layer 14.

The material of the current blocking layer 14 is not only SiO ₂ but also oxides such as SiON, Al ₂ O ₃ , TiO ₂ , ZrO ₂ , HfO ₂ , Nb ₂ O ₅ , nitrides such as AlN and SiN, and SiC Various insulators such as carbides, fluorides, etc. can be used. It may be a single layer or multiple layers of these materials, and may be single crystalline, polycrystalline or amorphous in any crystalline state. In addition, a dielectric multilayer film may be formed by alternately laminating two types of films having different optical indexes and 1⁄4 wavelength and different refractive indexes. Since the light traveling toward the p electrode 16 is reduced by the reflection by the current blocking layer 14 and the absorption of light by the p electrode 16 is reduced, the light emission efficiency can be further improved.

  The transparent electrode 15 is made of IZO (zinc-doped indium oxide). The transparent electrode 15 is continuously formed on the p layer 13 and the current blocking layer 14. Regions in which the p layer 13 and the transparent electrode 15 are in contact with each other in a plan view are light emitting regions 101a to 101d. The thickness of the transparent electrode 15 is 200 nm. As a material of the transparent electrode 15, other than IZO, indium oxide based materials such as ITO (indium tin oxide) and ICO (cerium-doped indium oxide) can be used, and other transparent conductive oxides can be used.

  In order to make light emission more uniform, the sheet resistance of the transparent electrode 15 is desirably 0.8 times to 1.2 times the sheet resistance of the n layer 11. More preferably, it is 0.9 times to 1.1 times, more preferably 0.95 times to 1.05 times.

  The p electrode 16 and the n electrode 17 are made of Ni / Au / Al. The Ni film is 50 nm, the Au film is 1500 nm, and the Al film is 10 nm. The planar pattern of the p electrode 16 is as shown in FIG. The circumferential portions 16 a and c and the arc portions 16 b and d of the p electrode 16 are located in predetermined regions on the transparent electrode 15. The connection portion 16 e of the p electrode 16 is located in the insulating film 18. The circumferential portions 16 a and c and the arc portions 16 b and d are connected in parallel by the connection portion 16 e. Further, the circumferential portions 17 a and c and the arc portions 17 b and d of the n electrode 17 are located in predetermined regions on the n layer 11 exposed by etching. The connection portion 17 e of the n-electrode 17 is located in the insulating film 18. The circumferential portions 17 a and c and the arc portions 17 b and d are connected in parallel by the connection portion 17 e.

  In the first embodiment, as shown in FIG. 3, the first element regions 100a to 100d are connected in parallel by the p electrode 16 and the n electrode 17. However, connection portions 16e and 17e of the p electrode 16 and the n electrode 17 are connected. It may be connected in series by changing the plane pattern of. A cross-sectional view taken along line B-B 'in the case of series connection is shown in FIG. However, parallel connection can improve the response speed, and can be more suitable for optical communication.

The insulating film 18 is made of SiO ₂ and is formed so as to cover the top surfaces of the first element regions 100a to 100d. In the insulating film 18, a p pad portion 16f made of Ti / Au / Al, a connection portion 16e, an n pad portion 17f, and a connection portion 17e are formed. The p pad portion 16f and the connection portion 16e are connected to the circumferential portions 16a and 16c and the arc portions 16b and d through the grooves. The n pad portion 17f and the connection portion 17e are connected to the circumferential portions 17a and 17c and the circular arc portions 17b and d through the grooves. Further, the insulating film 18 is not formed on a part of the p pad portion 16 f and the n pad portion 17 f, and the region is exposed.

  As described above, in the light emitting element of Example 1, the planar patterns of the light emitting regions 101a to 101d are circumferential or arc-shaped, and the arc-shaped plane pattern having the same center and central angle facing the inside and the outside. Since the p electrode 16 and the n electrode 17 are provided, the light emitting regions 101a to 101d can emit light uniformly, and it is possible to suppress a decrease in light output at high current.

  FIG. 5 is a plan view showing the configuration of the light emitting device of Example 2. As shown in FIG. 6 is a cross-sectional view showing the configuration of the light emitting device of Example 2. As shown in FIG. The cross sectional view of FIG. 6 is a cross section taken along line A-A 'in FIG. The light emitting device of Example 2 is the same as the light emitting device of Example 1 except for the planar patterns of the first device regions 100a to 100d, the second device region 100e, the light emitting regions 101a to 101d, the p electrode 16 and the n electrode 17 shown in FIG. The other configuration is the same as that of the first embodiment.

  As shown in FIG. 5, the light emitting element of Example 2 is a square having a side of 420 μm in plan view, and is electrically separated into the first element region 200 a and the second element region 200 b by the element isolation trench 29. ing. The first element region 200 a is connected by the p electrode 26 and the n electrode 27 and has a light emitting region 201 that emits light. On the other hand, the second element region 200b is not provided with the p electrode 26 and the n electrode 27, and does not emit light.

  The plane pattern of the first element region 200a is a circle as shown in FIG. The center O of the circle of the plane pattern of the first element region 200a is located near the center of one side 202a in the square plane pattern of the light emitting element.

  The second element region 200 b is a region which is separated by the element isolation trench 29 and exists outside the first element region 200 a. The p electrode 26 and the n electrode 27 are not connected to the second element region 200 b and are electrically separated from the first element region 200 a. Therefore, the second element region 200b is a region which does not emit light. The second element region 200 b functions as an absorption layer that absorbs light on the short wavelength side of the peak wavelength among the light emitted from the light emitting region 201. By this function, the half width of the emission spectrum becomes narrower and the directivity becomes higher. Therefore, light emission becomes more suitable for short distance optical communication using POF.

  The planar pattern of the light emitting region 201 is a circumferential shape (circular ring shape) contained in the first element region 200a. The center of the circumference which is a plane pattern of light emission field 201 is the same as the center O of the circle which is a plane pattern of the 1st element field 200a.

  The plane pattern of the p electrode 26 is a pattern of a circle which is the inside of the light emitting area 201 which is a circumferential plane pattern and whose center and the circumference of the plane pattern of the light emitting area 201 are the same.

  The plane pattern of the n electrode 27 is composed of a circumferential portion 27a which is a circumferential plane pattern, a pad portion 27b, and a connection portion 27c connecting these. The plane pattern of the circumferential portion 27a is a circle (ring shape) outside the light emitting area 201 which is a circumferential plane pattern and having the same center and circumference of the plane pattern of the light emitting area 201. It is a pattern.

  In the light emitting element of Example 2 described above, the planar pattern of the light emitting region 201, the p electrode 26, and the n electrode 27 is configured as described above, so that the same effect as that of Example 1 can be obtained. That is, the shortest distance from the p electrode 26 to the n electrode 27 is uniform, and the width of the light emitting region 201 in the direction of the shortest distance is also uniform. Therefore, the current flowing through the light emitting region 201 is even everywhere. Therefore, the light emitting region 201 can be made to emit light extremely uniformly, and a decrease in light output at high current can be suppressed.

  FIG. 8A is a graph showing the relationship between forward current and light output in the light emitting device of Example 2. FIG. The light output is a relative value based on the light output when the forward current is 5 mA. For comparison, the relationship between the forward current and the light output was examined also for the light emitting elements (light emitting elements of Comparative Examples 1 to 4) of the electrode patterns shown in FIG. 8B. In the light emitting element of Comparative Examples 1 to 4, the light emitting region is a rectangular planar pattern sandwiched between the p electrode and the n electrode. In Comparative Examples 1 to 4, the number of wiring patterns extending from the pad portion and the distance between them are changed, and in Comparative Example 1, only the pad portion in Comparative Example 1 and 1 each from the p pad portion and n pad portion in Comparative Example 2. In the wiring pattern of this embodiment, in the comparative example 3, one wiring pattern from the n pad portion, two wiring patterns from the p pad portion, in the comparative example 4, two wiring patterns from the n pad portion, p Three wiring patterns were formed from the pad portion.

  As shown in FIG. 8, the larger the number of wiring patterns and the shorter the distance, that is, the shorter the distance between the p electrode and the n electrode, the smaller the decrease in light output at high current, and the higher the current. It is the light emitting element of Example 2 that the light output decrease is the smallest.

  FIG. 9 is a plan view showing the configuration of the light emitting device of Example 3. FIG. The light emitting device of Example 3 is the same as the light emitting device of Example 1 except for the planar patterns of the first device regions 100a to 100d, the second device region 100e, the light emitting regions 101a to 101d, the p electrode 16 and the n electrode 17 shown in FIG. The other configuration is the same as that of the first embodiment.

  As shown in FIG. 9, the light emitting element of Example 3 is a square having a side of 420 μm in plan view, and is separated into four first element regions 300 a to 300 d by the element separation groove 39. The four first element regions 300a to 300d are connected in parallel by the p electrode 36 and the n electrode 37, and have light emitting regions 301a to 301d to emit light.

  The plane pattern of the first element region 300a is a circle as shown in FIG. 9, and the center O is located at the center near one side 102b in the square plane pattern of the light emitting element. The planar pattern of the first element regions 300b and 300c is arc-shaped with the center at O as shown in FIG. It is a double concentric pattern arranged in the order of the first element regions 300 b and c outside the first element region 300 a. The first element region 300d is a region outside the first element region 300c.

  The planar pattern of the light emitting region 301a is a circumferential shape (circular ring shape) included in the first element region 300a. The planar pattern of the light emitting area 301 b is an arc (a semicircular ring) having a central angle of 180 ° included in the first element area 300 b. The direction connecting the two ends of the arc is parallel to the side 102b. The planar pattern of the light emitting region 301c is an arc having a central angle of 120 ° included in the first element region 300b. The planar pattern of the light emitting area 301 d is an arc having a central angle of 80 ° included in the first element area 300 b. The center of the arc which is a plane pattern of the light emitting regions 301a to 301d is the same as the center O of a circle which is a plane pattern of the first element region 300a. In addition, the light emitting regions 301 b to d have a symmetrical pattern with respect to a central axis perpendicular to the side 102 and passing through the center O. Therefore, the mutual arrangement of the light emitting regions 301a to 301d is a concentric pattern symmetrical with respect to the central axis.

  The widths of circumferences or arcs which are planar patterns of the light emitting regions 301a to 301d are equal to one another. Further, assuming that the radius of the circumference (the distance from the center O to the center of the width of the circumference in the radial direction) which is a plane pattern of the light emitting area 301a is r, the radius of the arc which is a plane pattern of the light emitting area 301b is 2r. The radius of the arc that is the plane pattern of the light emitting area 301c is 3r, and the radius of the arc that is the plane pattern of the light emitting area 301d is 4.5r. Therefore, the areas of the planar patterns of the light emitting regions 301a to 301d are equal to one another.

  The planar pattern of the p electrode 36 includes a circumferential portion 36a which is a circumferential planar pattern, and arc portions 36b to 36d which are arcuate planar patterns having central angles of 180 °, 120 ° and 80 °, respectively, and And a connecting portion 36e which is a linear flat pattern connecting the two.

  The plane pattern of the circumferential portion 36a is an inner side of the light emitting area 301a which is a circumferential plane pattern, and the circumferential O of the plane pattern of the light emitting area 301a and the center O are the same (circular ring Pattern).

  The plane pattern of the arcs 36b to 36d faces the inside of the light emitting area 301b to d, which is an arc-shaped plane pattern, along the arc, and the arc O of the plane pattern of the light emitting areas 301b to 301d has the same center O and center angle. It is a circular arc-shaped pattern.

  The planar pattern of the connection portion 36e is a linear pattern extending from the circumferential portion 36a in the radial direction to one end of the arc portion 36d and connecting the circumferential portion 36a and the arc portions 36b to d.

  The plane pattern of the n electrode 37 includes: a circumferential portion 37a which is a circumferential plane pattern; and arc portions 37b to 37d which are arc plane patterns having central angles of 180 °, 120 °, and 80 °, respectively. And a pad portion 37f, which is a linear flat pattern connecting the two.

  The plane pattern of the circumferential portion 37a is a circle (a circular ring having the same center O as the circumference of the plane pattern of the light emitting area 301a, which is outside the light emitting area 301a which is a circumferential plane pattern. Pattern).

  The plane pattern of the arcs 37b to 37d faces the outside of the light emitting area 301b to d, which is an arc-shaped plane pattern, along the arc, and the arc O of the plane pattern of the light emitting area 301b to d is equal to the center O and the center angle. It is a circular arc-shaped pattern. The circular arc portion 37 d is connected to the pad portion 37 f of the flat pattern of the spatula type.

  The planar pattern of the connection portion 37e is a linear pattern extending from the circumferential portion 37a in the radial direction to one end of the circular arc portion 37d and connecting the circumferential portion 37a and the circular arc portions 37b to d.

In the light emitting device of Example 3 described above, the planar pattern of the light emitting regions 301a to 301d, the p electrode 36, and the n electrode 37 is configured as described above, so that the same effect as that of Example 1 can be obtained. That is, the shortest distance from the p electrode 36 to the n electrode 37 is uniform, and the widths of the light emitting regions 301a to 301d in the direction of the shortest distance are also uniform. Therefore, the current flowing through the light emitting regions 301a to 301d is even everywhere. Therefore, the light emitting regions 301a to 301d can be made to emit light extremely uniformly, and a decrease in light output at high current can be suppressed.
[Various modifications]

  The light emitting device of the present invention is characterized in the plane pattern and arrangement of the first element region, the light emitting region 101, and the p electrode and the n electrode, and is limited to the face-up type devices shown in the first to third embodiments. Alternatively, any conventionally known structure can be adopted.

  For example, the present invention can be applied to flip chip type devices and vertical type devices. Moreover, in Examples 1-3, it is applicable also to the structure which inverted the planar pattern of n layer and n electrode, and the planar pattern of p layer and p electrode. Even with such a reversed structure, it is not necessary to change the planar pattern of the light emitting region. FIG. 7 shows a cross section taken along the line A-A 'in the light emitting element of Example 2 in the case of such an inverted structure.

  Alternatively, without providing the current blocking layer 14, the p electrode may be in direct contact with the p layer in that region instead. Since the contact to the p layer is better for the transparent electrode than for the p electrode, current flows from the p electrode to the p layer through the transparent electrode and not to the region where the p electrode and p layer are in contact Therefore, the planar pattern of the light emitting region can be made similar.

  Among the various element structures, the present invention is particularly effective for flip chip type elements. In the flip chip type element, light is not shielded by the bonding wire at the time of mounting, and light emitted from the light emitting element can be efficiently incident on the core of the POF.

  The present invention is applicable to devices other than green light emitting devices with a center wavelength of 490 to 570 nm. However, the light emitting element of the present invention is particularly effective as a light source for optical communication by POF because the decrease in light output at high current is suppressed. Since POF has low loss in the green band, the light emitting device of the present invention should also emit green light with a center wavelength of 490 to 570 nm. More preferably, the center wavelength is 510 to 550 nm.

  The light emitting element of the present invention can be used as a light source for optical communication, and is particularly effective as a light source for short distance communication using POF.

10: substrate 11: n layer 12: light emitting layer 13: p layer 14: current blocking layer 15: transparent electrode 16, 26, 36: p electrode 17, 27, 37: n electrode 18: insulating film 100a to d, 200a, 300a to d: first element region 100e, 200b: second element region 101a to d, 201, 301a to d: light emitting region

Claims (6)

A light emitting device comprising a group III nitride semiconductor, having a plurality of first element regions for emitting light, wherein a p electrode and an n electrode are provided in each of the first element regions,
The planar pattern of each light emitting area of each of the first element areas is a circle or an arc;
The plane pattern of the entire light emitting area is set to be concentric circles or concentric arcs,
One plane pattern of the p electrode and the n electrode is provided opposite to the inside of the plane pattern of the circumference or arc of the light emitting region, and a circle whose center and central angle are the same as the circumference or arc, Fan-shaped, circumferential or arc,
The other plane pattern of the p electrode and the n electrode is provided to face the outside of the plane pattern of the arc of the light emitting area, and is a circle or arc having the same center and central angle as the circle or arc. Oh it is,
The first element regions are connected in parallel,
A light emitting element characterized by A second element region made of a group III nitride semiconductor, electrically isolated from the first element region outside the first element region, not provided with the p electrode and the n electrode and not emitting light Have
The light emitting device according to claim 1,   The area S of the plane pattern of each light emitting area is 0.9 × S 0 or more and 1.1 × S 0 or less, where an average value of the area of the plane pattern of each light emitting area is S 0. The light emitting device according to claim 1 or 2. The light emitting device according to any one of claims 1 to 3 , wherein a width of a circumference or an arc of the light emitting region is 5 to 20 m. The light emitting device according to any one of claims 1 to 4 , which emits green light. The light emitting device according to any one of claims 1 to 5 , which is a light source application of optical communication using a plastic optical fiber.