Light-emitting element

Abstract

To provide a face-up type ultraviolet light-emitting element, in which the light output is improved and the forward voltage is reduced.SOLUTION: A face-up type light-emitting element including a Group-III nitride semiconductor with an emission wavelength of 210 to 300 nm includes an n-type layer 11, an active layer 12 provided on the n-type layer 11, a p-type layer 13 provided on the active layer 12, an interdigital n-side electrode 17 provided on the n-type layer 11, a p-side contact electrode 14 provided on and in contact with the p-type layer 13 and transmitting light with the emission wavelength, and an interdigital p-side electrode 15 provided on the p-side contact electrode 14. The p-side electrode 15 includes a plurality of p-side extension parts 15A extending in a predetermined direction. The n-side electrode 17 includes a plurality of n-side extension parts 17A extending in a predetermined direction and disposed between the adjacent p-side extension parts 15A. The distance between the p-side extension part 15A and the n-side extension part 17A is 140 μm or less.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a light-emitting device. [Background technology]

[0002] Known light-emitting elements using group III nitride semiconductors are the flip-chip structure, which extracts light from the back side of the substrate, and the face-up structure, which extracts light from the opposite side to the substrate. In the case of blue light emission, the flip-chip type is used for high-output applications such as headlamps, while the face-up type is used for low-output applications such as backlights.

[0003] Furthermore, light-emitting elements using group III nitride semiconductors can emit light with wavelengths of 210 to 280 nm. It is known that ultraviolet light in the UVC range (100 to 280 nm) can efficiently sterilize and inactivate bacteria and viruses, and the market for UVC-LEDs using group III nitride semiconductors is expanding.

[0004] Patent documents 1 and 2 describe face-up UVC-LEDs. It is widely known that in face-up blue LEDs, the n-side electrode and the p-side electrode are comb-shaped. Patent documents 3 to 5 describe flip-chip UVC-LEDs that have the n-side electrode and the p-side electrode in a comb-shaped configuration. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2022-19963 [Patent Document 2] JP 2019-176016 A [Patent Document 3] JP 2017-28032 A [Patent Document 4] JP 2022-14593 A [Patent Document 5] JP 2022-43972 A Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, the market for UVC-LEDs has expanded, and face-up type UVC-LEDs are also in demand. However, face-up type UVC-LEDs have low light output and a high forward voltage Vf, so they have not been put to practical use.

[0007] The present invention has been made in view of the above background, and aims to provide a face-up type ultraviolet light-emitting element which is designed to improve the optical output and reduce the forward voltage. [Means for solving the problem]

[0008] One aspect of the present invention is A face-up type light-emitting device using a Group III nitride semiconductor having an emission wavelength of 210 to 300 nm, an n-type layer formed of an n-type Group III nitride semiconductor; an active layer formed on the n-type layer and made of a Group III nitride semiconductor; a p-type layer formed on the active layer and made of a p-type Group III nitride semiconductor; a comb-shaped n-side electrode provided on the n-type layer; a p-side contact electrode provided on and in contact with the p-type layer and transmitting light having an emission wavelength; a comb-shaped p-side electrode provided on the p-side contact electrode; Equipped with the p-side electrode includes a plurality of p-side extension portions extending in a predetermined direction, the n-side electrode includes a plurality of n-side extension portions extending in the predetermined direction and disposed between adjacent ones of the p-side extension portions; In the light-emitting device, the distance between the p-side extension portion and the n-side extension portion is 140 μm or less. Effect of the Invention

[0009] In the above embodiment, the p-side electrode and the n-side electrode are arranged in a comb-like shape, and the distance between the p-side extension of the p-side electrode and the n-side extension of the n-side electrode is set to 140 μm or less, thereby improving the light output and reducing the forward voltage. [Brief description of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view showing a configuration of a light-emitting element in an embodiment, the cross-section being perpendicular to a main surface of a substrate. [Diagram 2] FIG. 2 is a top view of the light-emitting element according to the embodiment, showing an electrode pattern. [Diagram 3] FIG. 13 is a diagram showing an electrode pattern of a light-emitting element of a comparative example. [Figure 4] Graph showing the relationship between forward current and light output. [Diagram 5] 1 is a graph showing current-voltage characteristics. [Figure 6] A graph showing the relationship between the number of n-side extensions and power conversion efficiency. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The light-emitting element is a face-up type light-emitting element having an emission wavelength of 210 to 300 nm, and uses a group III nitride semiconductor. The light-emitting element includes an n-type layer formed of an n-type group III nitride semiconductor, an active layer formed of a group III nitride semiconductor on the n-type layer, a p-type layer formed of a p-type group III nitride semiconductor on the active layer, a comb-shaped n-side electrode on the n-type layer, a p-side contact electrode on the p-type layer that transmits light of the emission wavelength, and a comb-shaped p-side electrode on the p-side contact electrode, the p-side electrode includes a plurality of p-side extensions extending in a predetermined direction, the n-side electrode includes a plurality of n-side extensions extending in the predetermined direction and disposed between adjacent p-side extensions, and the distance between the p-side extensions and the n-side extensions is 140 μm or less.

[0012] In the light emitting device, the distance between the p-side extension portion and the n-side extension portion may be 30 μm or more, which can suppress the inhibition of light extraction by the p-side electrode, and is more preferably 50 μm or more and 130 μm or less.

[0013] In the light-emitting device, the p-side contact electrode may be made of one oxide selected from the group consisting of ITO and IZO, and may have a thickness of 40 nm or less. The p-side contact electrode can transmit ultraviolet light of the emission wavelength while making good contact with the p-type layer.

[0014] In the light-emitting device, the p-side contact electrode may be made of one metal selected from the group consisting of Ru, Rh, Mg, an alloy mainly composed of these metals, and Ni / Au, and the thickness of the p-side contact electrode may be 10 nm or less. The p-side contact electrode can transmit ultraviolet light of the emission wavelength while making good contact with the p-type layer.

[0015] In the light-emitting device, the p-side electrode may include a p-side pad portion and a plurality of p-side extension portions extending from the p-side pad portion in a predetermined direction, the n-side electrode may include an n-side pad portion and a plurality of n-side extension portions extending from the n-side pad portion in a predetermined direction and disposed between adjacent p-side extension portions, the distance between the p-side pad portion and the n-side extension portion may be 150 μm or less, and the distance between the p-side extension portion and the n-side pad portion may be 150 μm or less. Also, in the light-emitting device, the distance between the p-side pad portion and the n-side extension portion may be 50 μm or more, and the distance between the p-side extension portion and the n-side pad portion may be 30 μm or more.

[0016] In the light emitting device, the distance between the center line of the p-side extension portion and the center line of the n-side extension portion may be 140 μm or less, which can improve the in-plane diffusion of current.

[0017] In the light-emitting device, the n-side extension portion and the p-side extension portion may have a width of 5 μm or more and 20 μm or less.

[0018] In the light-emitting device, the p-type layer may be in contact with the p-side contact electrode and include a p-type contact layer made of GaN, and the thickness of the p-type contact layer may be not less than 1 nm and not more than 50 nm.

[0019] In the light-emitting device, the p-type layer may be in contact with the p-side contact electrode and include a p-type contact layer made of AlGaN with an Al composition of 50% or less, and the thickness of the p-type contact layer may be 20 nm or less.

[0020] In the light emitting device, the number of n-side extension portions and p-side extension portions may be three or more, and in particular, from four to seven.

[0021] In the light-emitting device, an anti-reflection film may be provided on the p-side contact electrode in a region where the p-side electrode is not provided, or an anti-reflection film may be provided on the p-side contact electrode and an anti-reflection film may be provided on the p-side electrode in a region excluding the p-side pad portion.

[0022] (Embodiment 1) 1. Overview of light-emitting elements Fig. 1 is a cross-sectional view showing the configuration of the light-emitting element in the embodiment, which is a cross-section perpendicular to the main surface of the substrate. Fig. 2 is a top view of the light-emitting element in the embodiment, showing the electrode pattern. Fig. 1 is a cross-section taken along line II in Fig. 2.

[0023] As shown in FIG. 1 , the light-emitting element in the embodiment has a substrate 10, an n-type layer 11, an active layer 12, a p-type layer 13, a p-side contact electrode 14, a p-side electrode 15, an n-side contact electrode 16, an n-side electrode 17, an anti-reflection film 18, a protective film 19, an adhesion layer 20, and a back surface reflection film 21.

[0024] The light emitting element in the embodiment is a face-up type that extracts light from the side opposite to the substrate 10 (electrode side). The emission wavelength is a predetermined wavelength in the range of 210 to 300 nm, and can also be in the UVC band (100 to 280 nm).

[0025] 2. Light-emitting element configuration Next, each component of the light emitting element in the embodiment will be described in detail.

[0026] The substrate 10 is a substrate made of sapphire with the c-plane as the principal surface. The plane orientation of the principal surface of the sapphire may be the a-plane. The substrate may have an off-angle of 0.1 to 2 degrees in the m-axis direction. The substrate 10 may be an AlN substrate or an AlN template substrate in which an AlN layer is formed on a sapphire substrate.

[0027] The thickness of the substrate 10 is, for example, 1000 μm or less, and preferably 400 μm or more and 700 μm or less.

[0028] A back surface reflection film 21 is provided on the back surface of the substrate 10 via an adhesion layer 20. The adhesion layer 20 is a layer for improving adhesion between the substrate 10 and the back surface reflection film 21. The adhesion layer 20 is made of SiO 2 The back surface reflecting film 21 is made of a metal having a high reflectance to ultraviolet light of the emission wavelength. For example, it is Al, Mg, or an alloy containing them as a main component. By providing the back surface reflecting film 21, ultraviolet light emitted from the active layer 12 and proceeding toward the substrate 10 is reflected toward the electrode, thereby improving the light extraction efficiency. A DBR may be used as the back surface reflecting film 21.

[0029] The n-type layer 11 is located on the substrate 10. The n-type layer 11 is made of n-AlGaN. The Al composition (the molar ratio of Al in the whole group III metals) is, for example, 60 to 90%. The n-type impurity is Si, and the Si concentration is, for example, 1×10 18 ~5×10 19 cm -3 The thickness of the n-type layer 11 is, for example, 0.5 to 5 μm. The C concentration of the n-type layer 11 is 1×10 15 ~1×10 19 cm -3The n-type layer 11 may be composed of a plurality of layers. For example, it may be a superlattice layer in which AlGaN layers having different Al compositions are alternately stacked. Also, an underlayer made of AlN may be provided between the substrate 10 and the n-type layer 11. Also, an element other than Si may be used as the n-type impurity.

[0030] The active layer 12 is located on the n-type layer 11. The active layer 12 has an SQW structure in which a barrier layer, a well layer, and a barrier layer are stacked in this order from the n-type layer 11 side. The active layer 12 may have an MQW structure. In that case, the number of repetitions is, for example, 2 to 10.

[0031] The well layer is made of AlGaN, and the Al composition is set according to the desired emission wavelength. The Si concentration in the well layer is, for example, 1×10 18 cm -3 The well layer may be non-doped and has a thickness of, for example, 0.5 to 5 nm.

[0032] The barrier layer is made of AlGaN having a larger Al composition than the well layer, and the Al composition is, for example, 50 to 100%. The Si concentration of the barrier layer is, for example, 2×10 19 cm -3 or less, and may be non-doped. The thickness of the barrier layer is, for example, 3 to 30 nm. The barrier layer may be made of AlGaInN, which has a band gap energy larger than that of the well layer. In addition, the layer of the barrier layer that is in contact with the electron blocking layer preferably has a thickness of 0.5 to 10 nm.

[0033] A hole blocking layer may be provided between the n-type layer 11 and the active layer 12. This can prevent holes injected from the p-side electrode 15 from diffusing beyond the active layer 12 toward the n-type layer 11. The hole blocking layer is made of AlGaN or AlN having a higher Al composition than the barrier layer of the active layer 12. The thickness of the hole blocking layer is, for example, one molecular layer to 2 nm. In the case of AlN, one molecular layer is approximately 0.26 nm.

[0034] The p-type layer 13 is located on the active layer 12. The p-type layer 13 has a structure in which an electron block layer, a composition gradient layer, and a p-type contact layer are laminated in this order from the active layer 12 side.

[0035] The electron blocking layer has a two-layer structure in which a first electron blocking layer and a second electron blocking layer are stacked in this order from the active layer 12 side. The electron blocking layer prevents electrons injected from the n-side contact electrode 16 from diffusing beyond the active layer 12 toward the p-type layer 13 side.

[0036] The electron blocking layer does not necessarily have to have a two-layer structure, and may consist of only the first electron blocking layer.

[0037] The first electron blocking layer is made of AlGaN or AlN having a higher Al composition ratio than the barrier layer of the active layer 12, and the Al composition is, for example, 90 to 100%. The first electron blocking layer may be doped with a p-type impurity or may be undoped. The p-type impurity is, for example, Mg. When doped with Mg, the Mg concentration is, for example, 3×10 20 cm -3 The thickness of the first electron blocking layer is, for example, 1 to 10 nm.

[0038] The second electron block layer is made of AlGaN with a lower Al composition than the first electron block layer, and the Al composition is, for example, 80 to 99%. By providing the second electron block layer, the difference in Al composition with the composition gradient layer is adjusted. If the first electron block layer is made of AlN alone, the resistance will be high, and if the first electron block layer is made thin, the performance of the electron block will decrease. Therefore, by providing the second electron block layer, it is possible to achieve both low resistance and electron blocking function. In addition, the second electron block layer may be doped with p-type impurities, or may be undoped. In the case of Mg doping, the Mg concentration is, for example, 3×10 20 cm -3 The second electron blocking layer has a thickness of, for example, 1 to 10 nm.

[0039] The compositionally graded layer is located on the electron blocking layer and has a two-layer structure in which a first compositionally graded layer and a second compositionally graded layer are laminated in this order from the electron blocking layer side.

[0040] The compositionally graded layer is a layer that has been made p-type by a method called polarization doping. That is, the compositionally graded layer is a layer in which the Al composition changes in the thickness direction, and is set so that the Al composition decreases with increasing distance from the electron blocking layer. It was difficult to increase the hole concentration of AlGaN with a high Al composition by Mg doping, but polarization doping can improve the hole concentration and increase the efficiency of hole injection into the active layer 12. In addition, polarization doping does not require Mg doping, so crystallinity can be improved.

[0041] When the Al composition of the compositionally graded layer is set as above, polarization due to crystal distortion occurs continuously in the compositionally graded layer in the thickness direction. Holes are generated in the compositionally graded layer to cancel out the fixed charge caused by this polarization. The generated holes are distributed in the compositionally graded layer. Therefore, the holes are widely distributed in the thickness direction from the electron block layer side in the compositionally graded layer, and the layer becomes p-type overall. In this p-type region, the hole concentration is 1×10 16 ~1×10 20 cm -3 and the hole concentration decreases with increasing distance from the electron blocking layer.

[0042] The maximum value of the Al composition of the first composition gradient layer (the Al composition at the interface with the electron blocking layer) is preferably 1 to 20% lower than the Al composition of the electron blocking layer. The hole concentration can be further increased by polarization due to strain. For example, the maximum value of the Al composition is 65 to 95%.

[0043] In addition, the minimum value of the Al composition of the first composition gradient layer (the Al composition at the interface with the second composition gradient layer) is preferably 3 to 30% lower than the maximum value of the Al composition of the first composition gradient layer. The hole concentration can be further increased by polarization due to strain. In addition, the Al composition is preferably one having a band energy that does not absorb the emission wavelength.

[0044] The decrease rate of the Al composition of the first composition gradient layer is preferably 0.1 to 0.3% / nm. By setting the decrease rate in this range, the hole concentration of the first composition gradient layer can be further increased. The decrease rate of the Al composition may be constant, that is, may change linearly, or may not be constant.

[0045] The first composition gradient layer is undoped. However, it may be doped with Mg. This is expected to further increase the hole concentration by the p-type impurity. In this case, the Mg concentration is, for example, 1×10 20 cm -3 The following applies.

[0046] The second compositional gradient layer is a layer with a higher Mg concentration than the first compositional gradient layer, and the rest of the layer has the same Al composition as the first compositional gradient layer. In other words, the Al composition changes in the thickness direction, and the Al composition decreases with increasing distance from the electron blocking layer. Doping the second compositional gradient layer with Mg enables good connection to the p-type contact layer.

[0047] The difference between the maximum value of the Al composition of the second composition gradient layer (the Al composition at the interface with the first composition gradient layer) and the minimum value of the Al composition of the first composition gradient layer is 0 to 5%, and is preferably the same as the minimum value of the Al composition of the first composition gradient layer. In other words, it is preferable that the Al composition is continuous from the first composition gradient layer to the second composition gradient layer.

[0048] Moreover, the minimum value of the Al composition of the second composition gradient layer (the Al composition at the interface with the p-type contact layer) is preferably 3 to 30% lower than the maximum value of the Al composition of the second composition gradient layer.

[0049] The decrease rate of the Al composition of the second composition gradient layer is in the same range as the decrease rate of the Al composition of the first composition gradient layer, and may be the same as the decrease rate of the Al composition of the first composition gradient layer.

[0050] The Mg concentration of the second composition gradient layer is arbitrary as long as it is higher than the Mg concentration of the first composition gradient layer. 20 cm -3 It is preferable that the number of the electrodes is less than or equal to 100 in order to suppress the series resistance.

[0051] In the first embodiment, the Al composition of the composition gradient layer is decreased continuously, but it may be decreased stepwise. However, it is preferable that the region where the Al composition is constant is as small as possible.

[0052] The ratio of the thickness of the first composition gradient layer to the composition gradient layer is preferably 0.4 to 0.7. This range ensures sufficient improvement in hole concentration by polarization doping while also providing good contact between the composition gradient layer and the p-type contact layer. The ratio is more preferably 0.4 to 0.6.

[0053] The composition gradient layer does not necessarily have to have a two-layer structure of the first composition gradient layer and the second composition gradient layer, but may have only the first composition gradient layer.Furthermore, it may have a structure of three or more layers with different Al composition change rates, Mg concentrations, etc.

[0054] The ratio of the thickness of the composition gradient layer to the total thickness of the electron blocking layer, the composition gradient layer, and the p-type contact layer is preferably 50% or more and 90% or less. Within this range, the function as the p-type layer can be sufficiently improved.

[0055] Instead of the compositionally graded layer, a layer made of Mg-doped p-type AlGaN may be provided. In this case, the Mg concentration is, for example, 1×10 17 ~1×10 19 cm -3 The Al composition is, for example, 40 to 80%.

[0056] The p-type contact layer is located on the compositionally graded layer. The p-type contact layer is made of Mg-doped p-GaN. It may be p-AlGaN with an Al composition of 50% or less. More preferably, the Al composition is 30% or less.

[0057] When the p-type contact layer is made of GaN, the thickness is preferably 1 nm or more and 50 nm or less. GaN absorbs the ultraviolet light emitted from the active layer 12, but by making it sufficiently thin, it is possible to transmit the ultraviolet light. Therefore, a large decrease in the external quantum efficiency can be avoided. The thickness is preferably 1 nm or more and 10 nm or less. The Mg concentration of the p-type contact layer is, for example, 1×10 20 ~1×10 22 cm -3 It is.

[0058] When the p-type contact layer is AlGaN, it may be composed of multiple layers with different Al compositions and Mg concentrations. In this case, the thickness of the p-type contact layer is preferably 20 nm or less. By making it sufficiently thin, it is possible to transmit ultraviolet light. The Mg concentration is the same as in the case of GaN.

[0059] A groove 22 having a depth reaching the n-type layer 11 is provided in a partial region of the surface of the p-type layer 13. This groove 22 is for exposing the n-type layer 11 to provide the n-side contact electrode 16 and the n-side electrode 17. Therefore, the planar pattern of the groove 22 is a slightly enlarged pattern of the planar patterns of the n-side contact electrode 16 and the n-side electrode 17. The planar patterns of the n-side contact electrode 16 and the n-side electrode 17 will be described later.

[0060] The p-side contact electrode 14 is provided on and in contact with the p-type layer 13. The p-side contact electrode 14 is provided over the entire surface of the p-type layer 13 except for the ends. The p-side contact electrode 14 diffuses the current widely within the surface, increasing the light-emitting area and improving the light output.

[0061] The p-side contact electrode 14 is made of ITO. Other materials that can make good contact with the p-type contact layer and transmit ultraviolet light of the emission wavelength can be used. For example, conductive oxides such as IZO, Ru, Rh, Mg, alloys containing these as main components, and metals such as Ni / Au can be used. It is preferable to set the thickness so that the transmittance of ultraviolet light of the emission wavelength is 50% or more. When a conductive oxide is used, the thickness of the p-side contact electrode 14 is preferably 40 nm or less. When a metal is used, the thickness of the p-side contact electrode 14 is preferably 10 nm or less.

[0062] The p-side electrode 15 is provided on a partial region on the p-side contact electrode 14. The material of the p-side electrode 15 is, for example, Ti / Ni / Au / Al.

[0063] As shown in Fig. 2, the p-side electrode 15 has a comb-tooth-shaped planar pattern and includes a p-side extension 15A and a p-side pad 15B. The p-side extension 15A is a region provided for diffusing current in the plane. The p-side pad 15B is a region for providing a p-side pad electrode thereon. The p-side pad electrode is connected to the outside by a wire. The planar pattern of the p-side electrode 15 will be described in detail later.

[0064] The antireflection film 18 is provided in contact with the p-side contact electrode 14 in a region on the p-side contact electrode 14 where the p-side electrode 15 is not provided. The upper surface of the antireflection film 18 is in contact with the protective film 19. By providing the antireflection film 18, reflection between the p-side contact electrode 14 and the protective film 19 can be suppressed, and the light extraction efficiency from the upper surface of the element can be improved. Furthermore, the antireflection film 18 may be provided in contact with the p-side electrode 15 in a region on the p-side electrode 15 except for the p-side pad portion 15B. That is, the antireflection film may also be provided in contact with the p-side extension portion 15A. This can further improve the light extraction efficiency.

[0065] The anti-reflection film 18 is a single layer or a multi-layer in which materials with different refractive indices are alternately laminated, and has a structure in which the thickness of the layers is set to a predetermined value and reflection is reduced by optical interference. When the anti-reflection film 18 is a single layer, the refractive index of the anti-reflection film 18 (value at the emission wavelength) is preferably 1.4 to 1.9. For example, HfO 2 , ZrO 2 , SiO 2 , Al 2 O 3 , MgF 2 etc. can be used.

[0066] The n-side contact electrode 16 is provided on the n-type layer 11 exposed at the bottom surface of the groove 22. The material of the n-side contact electrode 16 is, for example, V / Al / Ti.

[0067] The n-side electrode 17 is provided on the n-side contact electrode 16. The material of the n-side electrode 17 is, for example, Ti / Ni / Au / Al. The p-side electrode 15 and the n-side electrode 17 may be made of the same material.

[0068] As shown in FIG. 2, the n-side contact electrode 16 and the n-side electrode 17 have a comb-like planar pattern and have an n-side extension 17A and an n-side pad 17B. The n-side extension 17A is a region provided for diffusing current in the plane. The n-side pad 17B is a region for providing an n-side pad electrode thereon. The n-side pad electrode is connected to the outside by a wire. Details of the planar patterns of the n-side contact electrode 16 and the n-side electrode 17 will be described later.

[0069] The protective film 19 is provided so as to cover the entire upper surface of the element except for the p-side pad portion 15B and the n-side pad portion 17B. The material of the protective film is SiO 2 And so on.

[0070] 2. Planar electrode pattern Next, the planar patterns of p-side electrode 15, n-side contact electrode 16, and n-side electrode 17 will be described with reference to FIG.

[0071] As shown in Fig. 2, the p-side electrode 15 has a comb-like shape and has five linear p-side extensions 15A and a p-side pad portion 15B connected to the p-side extensions 15A. The light-emitting element in the embodiment is rectangular in plan view, and the p-side extensions 15A extend from the vicinity of a certain edge of the rectangle in a direction perpendicular to the edge. The five p-side extensions 15A are arranged at equal intervals. The p-side pad portions 15B are arranged at the corners at both ends of a certain edge of the rectangle, and the p-side extensions 15A extend from the p-side pad portion 15B.

[0072] 2, the n-side contact electrode 16 and the n-side electrode 17 are comb-shaped and have four linear n-side extensions 17A and an n-side pad portion 17B connected to the n-side extensions 17A. The n-side extensions 17A extend in a direction perpendicular to the edge opposite to the edge where the p-side pad portion 15B is located. The n-side extensions 17A are located in the middle between the adjacent p-side extensions 15A. Two n-side pad portions 17B are located at a predetermined distance away near the edge opposite to the edge where the p-side pad portion 15B is located, and the n-side extensions 17A extend from the n-side pad portion 17B.

[0073] The distance D1 between the p-side extension 15A and the n-side extension 17A is 140 μm or less. By setting the distance D1 to 140 μm or less, the current can be efficiently diffused in the plane, improving the optical output and reducing the forward voltage. For the same reason, the distance D2 between the center line of the p-side extension 15A and the center line of the n-side extension 17A is preferably 140 μm or less.

[0074] Moreover, the distance D1 is preferably 30 μm or more. If the distance D1 is shorter, the area of ​​the p-side extension 15A increases, and the reflection and absorption of ultraviolet light by the p-side extension 15A inhibits light extraction. The distance D1 is preferably 50 μm or more and 130 μm or less, and more preferably 60 μm or more and 100 μm or less.

[0075] Also, the distance D3 between the p-side pad portion 15B and the n-side extension portion 17A is preferably 150 μm or less in order to efficiently diffuse the current in the plane. For the same reason, the distance D4 between the p-side extension portion 15A and the n-side pad portion 17B is preferably 150 μm or less.

[0076] The width W1 of the p-side extension 15A and the width W2 of the n-side extension 17A are preferably set to 5 μm or more and 20 μm or less. By setting the widths W1 and W2 in this manner, it is possible to achieve a balance between the current diffusion property of the p-side extension 15A and the n-side extension 17A and the reduction in the light-emitting area of ​​the p-side extension 15A and the n-side extension 17A.

[0077] In the embodiment, the p-side extension portion 15A is five and the n-side extension portion 17A is four, but this is not limited thereto. However, it is preferable that the p-side extension portion 15A and the n-side extension portion 17A are three or more, particularly four or more and seven or less. By making them four or more, the in-plane diffusibility of the current can be improved, and the light output can be greatly improved. In addition, the reason for making them seven or less is that the improvement in light output due to the increase in the number of the extension portions reaches a plateau at about seven, and the light output tends to decrease when the number of the extension portions exceeds seven. This is thought to be because, as the number of the extension portions increases, the area of ​​the p-side extension portion 15A and the n-side extension portion 17A increases, and the effect of the light extraction inhibition increases.

[0078] The light emitting element in the embodiment is rectangular in plan view. The length of the short side is, for example, 500 to 1500 μm, and the length of the long side is, for example, 500 to 1500 μm. Within this range, the p-side extension portion 15A and the n-side extension portion 17A can sufficiently improve the in-plane diffusibility of the current. The p-side extension portion 15A and the n-side extension portion 17A may be configured to extend in the long side direction or in the short side direction.

[0079] In the embodiment, two p-side pad portions 15B and two n-side pad portions 17B are provided, but the number is not limited to this and may be 1. However, by providing two or more p-side pad portions 15B and two or more n-side pad portions 17B, it becomes easier to diffuse the current uniformly in the plane.

[0080] 3. Summary In a face-up type light-emitting device with an emission wavelength of 210 to 300 nm, the p-side contact electrode 14 must be designed to transmit ultraviolet light of the emission wavelength. This requires thinning the p-side contact electrode 14. However, this results in poor in-plane current diffusion, leading to a decrease in light output and a deterioration in forward voltage.

[0081] Therefore, in the light-emitting device of the embodiment, the planar patterns of the p-side electrode 15, the n-side contact electrode 16, and the n-side electrode 17 are comb-shaped, the n-side extensions 17A are disposed between the adjacent p-side extensions 15A, and the distance between the p-side extensions 15A and the n-side extensions 17A is set to 140 μm or less. By setting the electrode pattern in this way, the in-plane diffusion of current can be improved, and the light output can be improved and the forward voltage can be reduced.

[0082] 4. Explanation of Experimental Results Experiment 1 A light emitting device (hereinafter referred to as the example light emitting device) was fabricated with a structure in which the anti-reflection film 18 was omitted from the light emitting device in the embodiment, and the light output and current-voltage characteristics were measured. The planar pattern of the electrodes was as shown in Figure 2, with D1 being 101 μm, D2 being 121 μm, D3 being 73 μm, D4 being 100 μm, W1 being 20 μm, and W2 being 20 μm. The area of ​​the p-side contact electrode 14 was 0.80 mm 2 , the area of ​​the n-side contact electrode 16 is 0.11 mm 2 The area of ​​the p-side electrode 15 is 0.13 mm 2 It was decided.

[0083] For comparison, a light-emitting device was fabricated in which the electrode pattern was changed as shown in FIG. 3 (hereinafter referred to as a comparative light-emitting device). The configuration other than the electrode pattern was the same as that of the light-emitting device of the embodiment. As shown in FIG. 3, the electrode pattern of the comparative light-emitting device has one less p-side extension 15A and one less n-side extension 17A compared to FIG. 2, with D1 set to 141 μm. Also, the area of ​​the p-side contact electrode 14 is 0.85 mm 2 The area of ​​the n-side contact electrode 16 is 0.09 mm 2 The area of ​​the p-side electrode 15 is 0.11 mm 2 It was decided.

[0084] Fig. 4 is a graph showing the relationship between forward current and optical output for the light-emitting elements of the Example and Comparative Example. The optical output is a standardized value with the optical output of the light-emitting element of the Example at 350 mA set to 1. As shown in Fig. 4, the light-emitting element of the Example has a higher optical output than the light-emitting element of the Comparative Example, and at 350 mA, the optical output of the light-emitting element of the Comparative Example was 98% of the optical output of the light-emitting element of the Example.

[0085] Fig. 5 is a graph showing the IV characteristics of the light-emitting elements of the Example and Comparative Example. As shown in Fig. 5, the light-emitting element of the Example had a lower forward voltage than the light-emitting element of the Comparative Example. At 350 mA, the forward voltage of the light-emitting element of the Comparative Example was 7.39 V, while the forward voltage of the light-emitting element of the Example was 6.78 V.

[0086] 4 and 5, it was found that the distance between the n-side extending portion 17A and the p-side extending portion 15A is preferably set to 140 μm or less.

[0087] Experiment 2 A simulation was performed to determine the power conversion efficiency (WPE) of a light-emitting device having the same structure as in Experiment 1, varying the number of n-side extensions 17A between 3 and 7. The light-emitting device was square in plan view, with each side measuring 1000 μm. The electrode pattern was the same as in Experiment 1, and the number of p-side extensions 15A was the number of n-side extensions 17A + 1. The width W1 of the p-side extensions 15A and the width W2 of the n-side extensions 17A were 20 μm.

[0088] Furthermore, the distance D1 between the p-side extending portion 15A and the n-side extending portion 17A varies depending on the number of the n-side extending portions 17A, as follows: for three, D1 is 161 μm, for four, D1 is 121 μm, for five, D1 is 97 μm, for six, D1 is 81 μm, and for seven, D1 is 69 μm.

[0089] FIG. 6 is a graph showing the relationship between the number of n-side extensions 17A and WPE (power conversion efficiency). As shown in FIG. 6, when the number of n-side extensions 17A is 4 or more, the power conversion efficiency increases significantly. This is thought to be because the in-plane diffusion of current improves with an increase in the number. In addition, when the number of n-side extensions 17A is increased from 5 to 6, the power conversion efficiency increases slightly, and when the number is 6, the power conversion efficiency reaches a maximum, and when the number is increased from 6 to 7, the power conversion efficiency decreases slightly. From this, it is thought that the power conversion efficiency will further decrease when the number is 8 or more. The reason why the power conversion efficiency decreases when the number of n-side extensions 17A is 7 or more is thought to be because the area of ​​the n-side extensions 17A and the p-side extensions 15A increases due to an increase in the number of n-side extensions 17A and the p-side extensions 15A, and light extraction deteriorates due to shielding by the electrodes.

[0090] 6, it was found that the number of n-side extending portions 17A is preferably 4 to 7, and more preferably 5 to 7. It was also found that the distance D1 between the p-side extending portion 15A and the n-side extending portion 17A is preferably 50 to 130 nm, and more preferably 60 to 100 nm. [Explanation of symbols]

[0091] 10: Substrate 11:n-type layer 12:Active layer 13:p-type layer 14: p-side contact electrode 15:p side electrode 15A:p side extension part 15B: p-side pad 16: n-side contact electrode 17:n side electrode 17A: n side extension part 17B: n-side pad 18: Anti-reflection film 19:Protective film 20: Adhesion layer 21: Back reflective film

Claims

1. A face-up type light-emitting device using a Group III nitride semiconductor having an emission wavelength of 210 to 300 nm, an n-type layer formed of an n-type Group III nitride semiconductor; an active layer formed on the n-type layer and made of a Group III nitride semiconductor; a p-type layer provided on the active layer and made of a p-type Group III nitride semiconductor; a comb-shaped n-side electrode provided on the n-type layer; a p-side contact electrode provided on and in contact with the p-type layer and transmitting light having an emission wavelength; a comb-shaped p-side electrode provided on the p-side contact electrode; Equipped with the p-side electrode includes a plurality of p-side extension portions extending in a predetermined direction, the n-side electrode includes a plurality of n-side extension portions extending in the predetermined direction and disposed between adjacent ones of the p-side extension portions; The light-emitting device, wherein the distance between the p-side extension portion and the n-side extension portion is 140 μm or less.

2. The light-emitting device according to claim 1 , wherein the distance between the p-side extension portion and the n-side extension portion is 30 μm or more.

3. the p-side contact electrode is made of one oxide selected from the group consisting of ITO and IZO, The light-emitting device according to claim 1 , wherein the p-side contact electrode has a thickness of 40 nm or less.

4. the p-side contact electrode is made of one metal selected from the group consisting of Ru, Rh, Mg, an alloy containing any of them as a main component, and Ni / Au; The light-emitting device according to claim 1 , wherein the p-side contact electrode has a thickness of 10 nm or less.

5. the p-side electrode includes a p-side pad portion and a plurality of the p-side extension portions extending from the p-side pad portion in the predetermined direction, the n-side electrode includes an n-side pad portion and a plurality of n-side extension portions extending from the n-side pad portion in the predetermined direction and disposed between adjacent p-side extension portions, the distance between the p-side pad portion and the n-side extension portion is 150 μm or less; 5. The light-emitting device according to claim 1, wherein the distance between the p-side extension and the n-side pad is 150 μm or less.

6. the distance between the p-side pad portion and the n-side extension portion is 50 μm or more; The light-emitting device according to claim 5 , wherein the distance between the p-side extension and the n-side pad is 30 μm or more.

7. 5. The light emitting device according to claim 1, wherein the distance between the center line of the p-side extension portion and the center line of the n-side extension portion is 140 μm or less.

8. 5. The light-emitting device according to claim 1, wherein the n-side extension portion and the p-side extension portion have a width of 5 μm or more and 20 μm or less.

9. the p-type layer is in contact with the p-side contact electrode and has a p-type contact layer made of GaN; 5. The light-emitting device according to claim 1, wherein the p-type contact layer has a thickness of 1 nm or more and 50 nm or less.

10. the p-type layer is in contact with the p-side contact electrode and has a p-type contact layer made of AlGaN having an Al composition of 50% or less; 5. The light-emitting device according to claim 1, wherein the p-type contact layer has a thickness of 20 nm or less.

11. 5. The light emitting device according to claim 1, wherein the number of the n-side extension portion and the p-side extension portion is three or more.

12. The light-emitting device according to claim 11 , wherein the number of the n-side extension portion and the p-side extension portion is 4 to 7.

13. 5. The light-emitting device according to claim 1, wherein the distance between the p-side extension portion and the n-side extension portion is 50 μm or more and 130 μm or less.

14. 5. The light-emitting device according to claim 1, further comprising an anti-reflection film provided on said p-side contact electrode in an area where said p-side electrode is not provided.

15. 6. The light-emitting device according to claim 5, further comprising an anti-reflection film provided on said p-side contact electrode, and further comprising an anti-reflection film provided on said p-side electrode except for said p-side pad portion.

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