Light-emitting element and insulating reflection prevention layer for light-emitting element

Abstract

Provided are: a light-emitting element which emits ultraviolet light in a face-up manner and which is capable of improving light extraction efficiency; and an insulating reflection prevention layer for use in the light-emitting element. The light-emitting element (1) is a light-emitting element that emits ultraviolet light in a face-up manner, and is provided with: an n-type layer (21) that is formed from an n-type group III nitride semiconductor; an active layer (22) that is provided on the n-type layer (21) and is formed of a group III nitride semiconductor; a p-type layer (23) that is provided on the active layer (22) and is formed of a p-type group III nitride semiconductor; a p-side electrode (50) provided on a portion of the p-type layer (23); and an insulating reflection prevention layer (60) that is provided on the other portion of the p-type layer (23), is formed of an insulating material, and prevents reflection of ultraviolet light having an emission wavelength.

Description

Technical Field

[0001] The present invention relates to a light emitting element and an insulating antireflection layer used for the light emitting element. Background Art

[0002] The wavelength of ultraviolet light of the solid-state light-emitting element using a group III nitride semiconductor corresponds to a wavelength band in the range of about 200nm to 400nm. In particular, it is known that UVC (wavelength 100nm to 280nm) can efficiently sterilize and disinfect, and the demand for group III nitride semiconductor light-emitting elements that radiate ultraviolet light with a wavelength corresponding to UVC is increasing. The ultraviolet light-emitting element has a structure in which an AlN layer is formed on a sapphire substrate and an n-type layer, an active layer, and a p-type layer formed of AlGaN are stacked on the AlN layer.

[0003] Patent documents 1, 2, and 3 describe face-up (FU) structures of ultraviolet light emitting elements. The ultraviolet light emitting elements described in Patent documents 1 and 2 include: a p-contact electrode disposed on a p-type semiconductor layer and composed of a transparent electrode such as ITO; and a p-electrode disposed on the p-contact electrode and composed of a stack of Ti, Rh, and Ti.

[0004] The ultraviolet light emitting element described in Patent Document 3 comprises: a transparent electrode disposed on a p-type semiconductor layer; and a protective layer disposed on the transparent electrode and formed of an insulating material that is transparent under the emission wavelength of ultraviolet light and protects the transparent electrode. The transparent electrode has a transparent metal layer, and the transparent metal layer is selected from the group consisting of Na, K, Cs, and Rb and has a light absorption coefficient of 5×104cm with respect to ultraviolet light of the emission wavelength. -1 The insulating material of the protective layer is MgF2.

[0005] Patent document 4 describes a face-up structure of a semiconductor light emitting element that emits blue light (wavelength 440nm to 460nm) different from ultraviolet light. The blue light emitting element described in FIG. 12 of Patent document 4 comprises: a transparent electrode film, which is disposed on a p-type semiconductor layer and is formed of ZnO or ITO; and a conductive multilayer antireflection layer, which is disposed on the transparent electrode film. The conductive multilayer antireflection layer is formed by x Ga 1-x The refractive index of InGaO3 is about 1.6, and that of Nb2O5 is about 2.4.

[0006] Patent Document 1: Japanese Patent Application Publication No. 2022-19963

[0007] Patent Document 2: Japanese Patent Application Publication No. 2019-176016

[0008] Patent Document 3: Japanese Patent Application Publication No. 2011-155084

[0009] Patent Document 4: Japanese Patent Application Publication No. 2014-22609

[0010] The light extraction efficiency of ultraviolet light emitting elements is lower than that of blue light emitting elements. In particular, in the face-up ultraviolet light emitting elements described in Patent Documents 1 to 3, the absorption of ultraviolet light by electrodes causes a decrease in light extraction efficiency. Summary of the invention

[0011] The present invention is completed in view of such background, and one of the purposes is to provide a face-up ultraviolet light-emitting element capable of improving light extraction efficiency. Another purpose of the present invention is to provide an insulating anti-reflection layer applied to a face-up ultraviolet light-emitting element and used to improve light extraction efficiency.

[0012] One embodiment of the present invention is a light-emitting element, which is a face-up ultraviolet light-emitting element and comprises: an n-type layer, which is formed of an n-type Group III nitride semiconductor; an active layer, which is arranged on the above-mentioned n-type layer and is formed of a Group III nitride semiconductor; a p-type layer, which is arranged on the above-mentioned active layer and is formed of a p-type Group III nitride semiconductor; a p-side electrode, which is arranged on a part of the above-mentioned p-type layer; and an insulating anti-reflection layer, which is arranged on another part of the above-mentioned p-type layer, is formed of an insulating material, and prevents reflection of ultraviolet light of the emission wavelength.

[0013] Another embodiment of the present invention is an insulating anti-reflection layer, which is used for a face-up ultraviolet light-emitting element and is arranged on a p-type layer and contains at least one selected from the group consisting of Hf oxide, Zr oxide, Si oxide, Al oxide, and Mg fluoride, and prevents reflection of ultraviolet light of the emission wavelength.

[0014] According to one embodiment of the present invention, a p-side electrode is formed in a local area on the p-type layer, and an insulating anti-reflection layer is formed in another local area. The insulating anti-reflection layer has a function of preventing reflection of ultraviolet light of the emission wavelength. Therefore, in the area where the insulating anti-reflection layer is configured, the light extraction efficiency of the ultraviolet light can be improved.

[0015] According to another aspect of the present invention, the insulating antireflection layer includes at least one selected from the group consisting of Hf oxide, Zr oxide, Si oxide, Al oxide, and Mg fluoride, thereby being able to exhibit a good antireflection effect on ultraviolet light of the emission wavelength.

[0016] As described above, according to the above aspect, a face-up ultraviolet light emitting element capable of improving light extraction efficiency can be provided. In addition, a reflection prevention layer for improving light extraction efficiency can be provided for a face-up ultraviolet light emitting element. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a cross-sectional view showing the structure of a light emitting element according to an embodiment.

[0018] Figure 2 Observed from above Figure 1 The light emitting element is shown as seen from above.

[0019] Figure 3 It is the result of Experiment 1 and is a graph showing the relationship between the thickness of the p-side transparent electrode and the transmittance of ultraviolet light with a wavelength of 280 nm.

[0020] Figure 4 It is the result of Experiment 2 and is a coordinate graph showing the relationship between the emission wavelength and the transmittance.

[0021] Description of Reference Numerals

[0022] 1...light-emitting element; 10...substrate; 20...semiconductor layer; 21...n-type layer; 22...active layer; 23...p-type layer; 23a...groove; 30...n-side electrode; 30a...wire-bonding portion; 30b...wiring portion; 31...first n-side electrode; 32...second n-side electrode; 40...p-side transparent electrode; 50...p-side electrode; 50a...wire-bonding portion; 50b...wiring portion; 60...insulating anti-reflection layer; 70...protective layer; 80...reflective layer. DETAILED DESCRIPTION

[0023] The light-emitting element is a face-up ultraviolet light-emitting element as described above, and comprises: an n-type layer, which is formed of an n-type Group III nitride semiconductor; an active layer, which is arranged on the above-mentioned n-type layer and is formed of a Group III nitride semiconductor; a p-type layer, which is arranged on the above-mentioned active layer and is formed of a p-type Group III nitride semiconductor; a p-side electrode, which is arranged on a part of the above-mentioned p-type layer; and an insulating anti-reflection layer, which is arranged on another part of the above-mentioned p-type layer, is formed of an insulating material, and prevents reflection of ultraviolet light of the emission wavelength.

[0024] Alternatively, the light emitting element further comprises a p-side transparent electrode, the p-side transparent electrode is disposed on the p-type layer in contact with the p-type layer and transmits ultraviolet light of the emission wavelength, the p-side electrode is disposed on a part of the p-side transparent electrode, and the insulating anti-reflection layer is disposed on another part of the p-side transparent electrode. By disposing the p-side transparent electrode on the p-type layer, the contact resistance with the p-type layer can be reduced, and the light emitting efficiency can be improved.

[0025] The refractive index of the insulating antireflection layer may be set between the refractive index of the p-side transparent electrode and the refractive index of air. This can improve light extraction efficiency.

[0026] Furthermore, the insulating antireflection layer may have a multilayer structure in which materials having different refractive indices are stacked. This allows the reflections to be weakened by interference of light, thereby improving light extraction efficiency.

[0027] Furthermore, the insulating antireflection layer may include at least one selected from the group consisting of Hf oxide, Zr oxide, Si oxide, Al oxide, and Mg fluoride. Thus, the insulating antireflection layer can be formed to have a desired function.

[0028] In addition, the p-side transparent electrode may be formed to be thinner than the insulating anti-reflection layer. Thus, the transmittance of ultraviolet light at the p-side transparent electrode can be increased, and the anti-reflection function at the insulating anti-reflection layer can be improved. As a result, the light extraction efficiency can be improved.

[0029] In addition, the thickness of the p-side transparent electrode may be less than 40 nm. Thus, the transmittance of ultraviolet light at the p-side transparent electrode can be increased. In addition, the thickness of the insulating anti-reflection layer may be greater than 1 nm and less than 300 nm. In addition, the p-type layer may be GaN or AlGaN.

[0030] (Implementation Method)

[0031] 1. Structure of Light Emitting Element 1

[0032] Reference Figure 1 and Figure 2 The structure of the light emitting element 1 of this embodiment will be described. Figure 1 It is a cross-sectional view in a direction perpendicular to the main surface of the substrate. Figure 2 It is a diagram showing a planar pattern of the light emitting element 1 according to the present embodiment. Figure 1 The cross section and Figure 2 The AA section corresponds to.

[0033] like Figure 1As shown, the light emitting element 1 of this embodiment includes a substrate 10, a semiconductor layer 20, an n-side electrode 30, a p-side transparent electrode 40, a p-side electrode 50, an insulating anti-reflection layer 60, a protective layer 70, and a reflective layer 80. The light emitting element 1 has a face-up type, that is, the surface ( Figure 1 In addition, the light emitting element 1 is a light emitting element that emits ultraviolet light with a wavelength of 100nm to 400nm, and in particular, a light emitting element that emits deep ultraviolet light with a wavelength of 100nm to 280nm (UVC band).

[0034] The substrate 10 is, for example, a substrate formed of sapphire. The plane coordination (Japanese: orientation) of the main surface of the substrate 10 is, for example, an a-plane or a c-plane. In addition, the substrate 10 may have an off-angle of 0.1 to 2 degrees in the m-axis direction. In addition to sapphire, any material may be used for the substrate 10 as long as it has a high transmittance relative to the emission wavelength and can grow a III-nitride semiconductor crystal. For example, the substrate 10 may be an AlN substrate or an AlN template substrate having an AlN layer formed on a sapphire substrate.

[0035] The semiconductor layer 20 is formed on the main surface of the substrate 10 by crystal growth. The semiconductor layer 20 includes a group III nitride semiconductor. The semiconductor layer 20 includes at least an n-type layer 21, an active layer 22, and a p-type layer 23. The semiconductor layer 20 is composed of the n-type layer 21, the active layer 22, and the p-type layer 23 stacked in order from the substrate 10 side.

[0036] The n-type layer 21 is provided on the substrate 10. The n-type layer 21 is formed of an n-type group III nitride semiconductor. The n-type layer 21 is formed of, for example, n-AlGaN. The Al composition of the n-type layer 21 (the molar ratio of Al in the entire group III metal) is, for example, 60% to 90%. The n-type impurity of the n-type layer 21 is Si, and the Si concentration is, for example, 1×10 18 cm -3 ~5×10 19 cm -3 The thickness of the n-type layer 21 is, for example, 0.5 μm to 5 μm. In addition, the C concentration of the n-type layer 21 is 1×10 15 cm -3 ~1×10 19 cm -3 The n-type layer 21 may be composed of a plurality of layers. For example, the n-type layer 21 may be a superlattice layer in which AlGaN with different Al compositions are alternately stacked. In addition, a base layer formed of AlN may be provided between the substrate 10 and the n-type layer 21. In addition, a substance other than Si may be used as an n-type impurity.

[0037] The active layer 22 is provided on the n-type layer 21. The active layer 22 is formed of a group III nitride semiconductor. The active layer 22 is an SQW structure in which a barrier layer, a well layer, and a barrier layer are stacked in order from the n-type layer 21 side. The active layer 22 may also be an MQW structure. In this case, the number of repetitions of the MQW structure is, for example, 2 to 10.

[0038] The well layer is made of AlGaN, and its Al composition is set according to the desired emission wavelength. The Si concentration of the well layer is, for example, 1×10 18 cm -3 Hereinafter, the well layer may be non-doped. In addition, the thickness of the well layer is, for example, 0.5 nm to 5 nm.

[0039] The barrier layer is AlGaN with a higher Al content than the well layer. The Al content is, for example, 50% to 100%. The Si concentration of the barrier layer is, for example, 2×10 19 cm -3 Hereinafter, the barrier layer may be non-doped. The thickness of the barrier layer is, for example, 3 nm to 30 nm. The barrier layer may be AlGaInN having a larger band gap energy than the well layer.

[0040] Alternatively, a hole blocking layer may be provided between the n-type layer 21 and the active layer 22. The hole blocking layer can prevent holes injected from the p-side electrode 50 from diffusing to the n-type layer 21 side beyond the active layer 22. The hole blocking layer is formed of AlGaN or AlN having a higher Al composition than the barrier layer of the active layer 22. The thickness of the hole blocking layer is, for example, 1 molecular layer to 2 nm. In the case of AlN, 1 molecular layer is approximately 0.26 nm.

[0041] The p-type layer 23 is provided on the active layer 22. The p-type layer 23 is formed of a group III nitride semiconductor. The p-type layer 23 constitutes a layer in contact with the electrode, and therefore is also called a p-type contact layer. The p-type layer 23 may also be Mg-doped p-GaN or p-AlGaN. When the p-type layer 23 is p-AlGaN, the Al component is, for example, less than 50%, preferably less than 30%.

[0042] When the p-type layer 23 is GaN, the thickness of the p-type layer 23 is preferably 1 nm or more and 50 nm or less. GaN may absorb ultraviolet light radiated from the active layer 22, but by being sufficiently thinned, ultraviolet light can be transmitted. Therefore, a significant decrease in external quantum efficiency can be avoided. The thickness of the p-type layer 23 is preferably 1 nm or more and 10 nm or less. The Mg concentration of the p-type layer 23 is, for example, 1×10 20 cm -3 ~1×10 22 cm -3 .

[0043] Alternatively, the p-type layer 23 may be composed of a plurality of layers with different Al components and Mg concentrations. In the case where the p-type layer 23 is composed of a plurality of layers, the uppermost layer in contact with the p-side transparent electrode 40 is preferably p-GaN or AlGaN with a low Al component. This is to reduce the contact resistance with the p-side transparent electrode 40. In this case, the AlGaN with a low Al component is less than 50% of the Al component, preferably less than 30%. In the case where the p-type layer 23 is AlGaN with an Al component of less than 50%, the thickness is preferably less than 20 nm. Sufficient thinning enables ultraviolet light to pass through.

[0044] A groove 23a having a depth reaching the n-type layer 21 is formed in a local region of the surface of the p-type layer 23. The groove 23a is a structure for exposing the n-type layer 21 and providing the n-side electrode 30.

[0045] Alternatively, an electron blocking layer may be provided between the active layer 22 and the p-type layer 23. The electron blocking layer can prevent electrons injected from the n-side electrode 30 from diffusing to the p-type layer 23 side beyond the active layer 22. The electron blocking layer is formed of a group III nitride semiconductor. The electron blocking layer is formed of AlGaN or AlN having a higher Al composition ratio than the barrier layer of the active layer 22. The electron blocking layer may be doped with p-type impurities such as Mg, or may be undoped. The thickness of the electron blocking layer is, for example, 1 nm to 20 nm.

[0046] Alternatively, a composition-gradient layer may be provided between the electron blocking layer and the p-type layer 23. The composition-gradient layer is formed of a group III nitride semiconductor. The composition-gradient layer is a layer that becomes p-type by a method called polarization doping. That is, the composition-gradient layer is a layer in which the Al composition changes in the thickness direction, and is set so that the Al composition decreases as it moves away from the electron blocking layer. The Al composition of the p-type layer 23 is lower than the minimum Al composition of the composition-gradient layer. If AlGaN with a high Al composition is doped with Mg, it is not easy to increase the hole concentration, but the hole concentration can be increased by polarization doping, which can improve the hole injection efficiency for the active layer 22. In addition, if polarization doping is used, Mg may not be doped, and therefore, the crystallinity can be improved.

[0047] The n-side electrode 30 is provided on the n-type layer 21 exposed at the bottom surface of the groove 23a and is in contact with the n-type layer 21. Figure 2 As shown in FIG. 1 , when the light emitting element 1 is viewed from above, the n-side electrode 30 is composed of a wire bonding portion 30a and a wiring portion 30b. The wire bonding portion 30a is provided on one side ( Figure 2 The wire connecting portion 30a is connected to a wire material not shown in the figure. The wire connecting portion 30a is formed in any shape such as a bowl, a rectangle, or a circle.

[0048] The wiring portion 30b extends from the wire bonding portion 30a. The width of the wiring portion 30b is smaller than the diameter of the wire bonding portion 30a. The wiring portion 30b extends, for example, along an edge of the substrate 10 adjacent to an edge where the wire bonding portion 30a is formed. In this embodiment, a plurality of (for example, two) wiring portions 30b extend from the wire bonding portion 30a in a fork shape. However, it is also possible that only one wiring portion 30b extends from the wire bonding portion 30a.

[0049] In addition, if Figure 1 As shown, the n-side electrode 30 has a first n-side electrode 31 and a second n-side electrode 32 in a direction perpendicular to the main surface of the substrate 10. The first n-side electrode 31 is provided on the n-type layer 21 exposed at the bottom surface of the groove 23a and is in contact with the n-type layer 21. The first n-side electrode 31 is formed of V / Al / Ti, Ti / Al, V / Al, etc. Here, A / B means that A and B are stacked in order from the n-type layer 21 side. The thickness of the first n-side electrode 31 is 100nm to 300nm.

[0050] The second n-side electrode 32 is provided on the first n-side electrode 31 so as to be in contact with the first n-side electrode 31. The second n-side electrode 32 is formed of Ti / Ni / Au / Al, Ti / Pt / Au / Al, etc. The thickness of the second n-side electrode 32 is 300 nm to 600 nm.

[0051] The p-side transparent electrode 40 is in contact with the p-type layer 23 and is disposed on the p-type layer 23. The p-side transparent electrode 40 is disposed on the entire surface of the substrate 10 except for the periphery and the groove 23a. The p-side transparent electrode 40 transmits ultraviolet light of the emission wavelength. The p-side transparent electrode 40 is formed of ITO, IZO, NiAu, Rh, Ru, Mg, etc. These materials can achieve good contact with the p-type layer 23. When the p-side transparent electrode 40 is ITO, the refractive index of the p-side transparent electrode 40 is 2 to 2.5.

[0052] The thickness of the p-side transparent electrode 40 is 40 nm or less, preferably 20 nm or less. By setting the thickness of the p-side transparent electrode 40 as described above, the transmittance of ultraviolet light can be improved. In addition, the p-side transparent electrode 40 is 1 nm or more, preferably 3 nm or more. By setting the thickness of the p-side transparent electrode 40 as described above, good contact can be achieved with respect to the p-type layer 23.

[0053] The p-side transparent electrode 40 is configured to have a transmittance of 30% or more for ultraviolet light of a predetermined emission wavelength, preferably a transmittance of 50% or more for ultraviolet light of a predetermined emission wavelength. For example, the p-side transparent electrode 40 may also be configured to have a transmittance of 30% or more for ultraviolet light of a wavelength of 280 nm, preferably a transmittance of 50% or more for ultraviolet light of a wavelength of 280 nm. By making the thickness of the p-side transparent electrode 40 less than 40 nm as described above, the transmittance of ultraviolet light of a wavelength of 280 nm can be made more than 30%. In addition, by making the thickness of the p-side transparent electrode 40 less than 20 nm, the transmittance of ultraviolet light of a wavelength of 280 nm can be made more than 50%.

[0054] The p-side electrode 50 is provided on a portion of the p-side transparent electrode 40 and is in contact with a portion of the p-side transparent electrode 40 . Therefore, the p-side electrode 50 is provided on a portion of the p-type layer 23 .

[0055] like Figure 2 As shown, in a plan view of the light emitting element 1, the p-side electrode 50 is composed of a wire bonding portion 50a and a wiring portion 50b. The wire bonding portion 50a is provided on the side opposite to the wire bonding portion 30a of the n-side electrode 30 among the four sides of the rectangular substrate 10 ( Figure 2 The wire connecting portion 50a is connected to a wire material not shown in the figure. The wire connecting portion 50a is formed in any shape such as a circle, a rectangle, or a bowl.

[0056] The wiring portion 50b extends from the wire bonding portion 50a. The width of the wiring portion 50b is smaller than the diameter of the wire bonding portion 50a. The wiring portion 50b extends, for example, along the side of the substrate 10 adjacent to the side where the wire bonding portion 50a is formed. In this embodiment, one wiring portion 50b extends from the wire bonding portion 30a. The one wiring portion 50b is located between the two wiring portions 30b of the n-side electrode 30. However, the wiring portion 50b of the p-side electrode 50 may extend in a plurality of ways like a fork shape.

[0057] The p-side electrode 50 is formed of Ti / Ni / Au / Al, Ti / Pt / Au / Al, etc. The thickness of the p-side electrode 50 is 300 nm to 600 nm. The p-side electrode 50 is formed thicker than the p-side transparent electrode 40. The p-side electrode 50 can be formed simultaneously with the second n-side electrode 32.

[0058] The insulating anti-reflection layer 60 is provided on another part of the p-side transparent electrode 40. In other words, the insulating anti-reflection layer 60 is provided in a region of the p-side transparent electrode 40 that is different from the region where the p-side electrode 50 is arranged. In particular, the insulating anti-reflection layer 60 is provided entirely on the upper surface of the p-side transparent electrode except for the portion in contact with the p-side electrode 50. Therefore, when the light emitting element 1 is viewed from above, the area of ​​the insulating anti-reflection layer 60 is larger than the area of ​​the portion in contact with the p-side transparent electrode 40 of the p-side electrode 50.

[0059] The insulating anti-reflection layer 60 is formed of an insulating material, prevents reflection of ultraviolet light of the emission wavelength, and allows ultraviolet light of the emission wavelength to pass through. The refractive index of the insulating anti-reflection layer 60 is set between the refractive index of the p-side transparent electrode 40 (n=2 to 2.5) and the refractive index of air (n=about 1). For example, the refractive index of the insulating anti-reflection layer 60 is preferably set to 1.4 to 1.9.

[0060] The insulating antireflection layer 60 includes at least one selected from the group consisting of Hf oxide, Zr oxide, Si oxide, Al oxide, and Mg fluoride. For example, the insulating antireflection layer 60 includes HfO2, ZrO2, SiO2, Al2O3, MgF2, and the like.

[0061] The insulating anti-reflection layer 60 may have a single-layer structure or a multi-layer structure. Alternatively, when the insulating anti-reflection layer 60 has a multi-layer structure, it may be a structure in which materials with different refractive indices are stacked, and the thickness of each layer is set so that reflections are mutually weakened by light interference. For example, the insulating anti-reflection layer 60 is a structure in which a plurality of materials with different refractive indices are stacked.

[0062] The structure of the laminated film of 1.5 to 2.0 / 1.0 to 1.5 / 1.5 to 2.0 or the structure in which these laminated films are laminated multiple times, etc. The number of times of lamination is 1 to 3 times.

[0063] The thickness of the insulating antireflection layer 60 is 1 nm to 300 nm. The insulating antireflection layer 60 is formed thicker than the thickness of the p-side transparent electrode 40. In other words, the p-side transparent electrode 40 is formed thinner than the thickness of the insulating antireflection layer 60. In addition, the insulating antireflection layer 60 has a thickness comparable to that of the p-side electrode 50.

[0064] The protective layer 70 is provided to cover the upper surface side of the light emitting element 1. The protective layer 70 is formed of an insulating material, for example, SiO2, SiN, or the like.

[0065] Specifically, the protective layer 70 covers the exposed surface of the n-type layer 21, the exposed surface of the p-type layer 23, the exposed surface of the wiring portion 30b of the n-side electrode 30, the exposed surface of the p-side transparent electrode 40, the exposed surface of the wiring portion 50b of the p-side electrode 50, and the exposed surface of the insulating anti-reflection layer 60. However, the protective layer 70 is not formed on the upper surface of the wire bonding portion 30a of the n-side electrode 30, and the wire bonding portion 30a is exposed in a manner that allows the wire bonding (not shown). Similarly, the protective layer 70 is not formed on the upper surface of the wire bonding portion 50a of the p-side electrode 50, and the wire bonding portion 50a is exposed in a manner that allows the wire bonding (not shown).

[0066] The reflective layer 80 is disposed on the back side of the substrate 10 ( Figure 1 The lower surface of the substrate 10 and the surface on the opposite side to the light extraction side). The reflective layer 80 reflects the ultraviolet light emitted by the active layer 22 in the direction of light extraction. The reflective layer 80 may also have a single-layer structure or a multi-layer structure. The reflective layer 80 includes, for example: a first layer provided in contact with the back side of the substrate 10 and a second layer provided in contact with the back side of the first layer. The first layer is formed of, for example, SiO2, SiN, etc. The second layer is composed of a reflective film formed of, for example, Al, Rh, Ru, Mg, Al, Ti / Ni / Au, etc., and a close-contact layer formed on the back side of the reflective film and in close contact with the metal paste. The reflective film of the second layer can also be applied with materials other than metals. The reflective layer 80 can also use a distributed Bragg reflector (DBR).

[0067] 2. Experiment (Experiment 1)

[0068] As Experiment 1, the transmittance of ultraviolet light with a wavelength of 280 nm was measured using a test body 1 in which ITO corresponding to the p-side transparent electrode 40 was formed on the main surface of a sapphire substrate. As the test body 1, the thickness of ITO was 5 types: 16 nm, 18 nm, 32 nm, 42 nm, and 105 nm.

[0069] When the thickness of ITO is 16 nm, 18 nm, 32 nm, 42 nm, and 105 nm, the transmittance is 56%, 54%, 42%, 36%, and 12%.

[0070] like Figure 3 As shown in FIG. 1 , the results of Experiment 1 show that the transmittance of ITO can be 35% or more by setting the thickness of ITO to 40 nm or less, and can be 50% or more by setting the thickness of ITO to 20 nm or less.

[0071] (Experiment 2)

[0072] Next, as Experiment 2, the relationship between the emission wavelength and the transmittance was measured using test pieces 2A and 2B in which ITO corresponding to the p-side transparent electrode 40 was formed on the main surface of the sapphire substrate, and a layer corresponding to the insulating anti-reflection layer 60 was further formed on the ITO. The thickness of the ITO in test piece 2A was 16 nm, and the thickness of the ITO in test piece 2B was 100 nm. In test pieces 2A and 2B, the layer corresponding to the insulating anti-reflection layer 60 was formed by a laminated film having a refractive index of 1.5 to 2.0 / 1.0 to 1.5 / 1.5 to 2.0, and the thickness of the layer corresponding to the insulating anti-reflection layer 60 was 250 nm.

[0073] As a comparative example, the relationship between the emission wavelength and the transmittance was also measured for test pieces 3A and 3B in which ITO corresponding to the p-side transparent electrode 40 was formed on the main surface of the sapphire substrate. Test pieces 3A and 3B did not have a layer corresponding to the insulating anti-reflection layer 60. The thickness of ITO was 16 nm for test piece 3A, and 100 nm for test piece 3B.

[0074] like Figure 4 As shown, according to the results of Experiment 2, at a wavelength of 280 nm, the transmittance of the test piece 2A is 68.8%, the transmittance of the test piece 2B is 13.1%, the transmittance of the test piece 3A is 56.8%, and the transmittance of the test piece 3B is 11.5%.

[0075] When the test body 2A is compared with the test body 3A of the comparative example, it is found that the transmittance of the test body 2A is increased by 12% compared with the test body 3A of the comparative example. When the test body 2B is compared with the test body 3B of the comparative example, the transmittance of the test body 2B is increased by 1.5% compared with the test body 3B of the comparative example. According to the above content, by providing the insulating anti-reflection layer 60, the transmittance at a wavelength of 280nm can be improved.

[0076] Furthermore, when the test piece 2A is compared with the test piece 2B, it can be seen that the transmittance of the test piece 2A is increased by 55.7% compared with the test piece 2B. Therefore, by making the p-side transparent electrode 40 thinner, the transmittance at a wavelength of 280 nm can be improved.

[0077] In other wavelength bands, such as Figure 4 As shown, it can be seen that the test body 2A has a high transmittance in the wavelength band below 350nm. In particular, the transmittance of the test body 2A in the wavelength band of 200nm to 350nm is generally above 50%. Therefore, by becoming the structure of the test body 2A, the light extraction efficiency of ultraviolet light can be improved.

[0078] 3. Effect

[0079] According to the light-emitting element 1 of this embodiment, a p-side electrode 50 is formed on the p-type layer 23 and in a local area, and an insulating anti-reflection layer 60 is formed in another local area. The insulating anti-reflection layer 60 has a function of preventing reflection of ultraviolet light of the emission wavelength. Therefore, the light extraction efficiency of ultraviolet light in the area where the insulating anti-reflection layer 60 is arranged can be improved. In this way, the light extraction efficiency in the face-up ultraviolet light-emitting element can be improved.

[0080] Alternatively, the refractive index of the insulating anti-reflection layer 60 may be set between the refractive index of the p-side transparent electrode 40 and the refractive index of air. Thus, the light extraction efficiency can be improved. In particular, the insulating anti-reflection layer 60 may have a multilayer structure in which materials with different refractive indices are stacked. Thus, it can be set so that reflections are mutually weakened by interference of light, and as a result, the light extraction efficiency can be improved.

[0081] Furthermore, the insulating antireflection layer 60 may include at least one selected from the group consisting of Hf oxide, Zr oxide, Si oxide, Al oxide, and Mg fluoride. In this way, the insulating antireflection layer 60 can be formed to have a desired function.

[0082] In addition, in the light emitting element 1, by providing the p-side transparent electrode 40 on the p-type layer 23, the contact resistance with the p-type layer 23 can be reduced, and the luminous efficiency can be improved. At this time, the p-side transparent electrode 40 is preferably formed to be thinner than the thickness of the insulating anti-reflection layer 60. In particular, the thickness of the p-side transparent electrode 40 is preferably 40nm or less, preferably 20nm or less. Thus, the transmittance of ultraviolet light of the p-side transparent electrode 40 can be improved, and the anti-reflection function of the insulating anti-reflection layer 60 can be improved. As a result, the light extraction efficiency can be improved.

Claims

1. A light-emitting element, which is a face-up ultraviolet light-emitting element, characterized in that: have: An n-type layer formed of an n-type Group III nitride semiconductor; an active layer disposed on the n-type layer and formed of a Group III nitride semiconductor; a p-type layer disposed on the active layer and formed of a p-type Group III nitride semiconductor; A p-side electrode disposed on a portion of the p-type layer; and The insulating antireflection layer is provided on another part of the p-type layer and is formed of a material having insulating properties and prevents reflection of ultraviolet light of the emission wavelength.

2. The light emitting element according to claim 1, characterized in that It also includes a p-side transparent electrode, which is disposed on the p-type layer and in contact with the p-type layer and transmits ultraviolet light of a light emission wavelength. The p-side electrode is disposed on a portion of the p-side transparent electrode. The insulating antireflection layer is provided on another part of the p-side transparent electrode.

3. The light emitting element according to claim 2, characterized in that The refractive index of the insulating antireflection layer is set between the refractive index of the p-side transparent electrode and the refractive index of air.

4. The light-emitting element according to any one of claims 1 to 3, characterized in that The insulating antireflection layer has a multilayer structure in which materials having different refractive indices are stacked.

5. The light emitting element according to any one of claims 1 to 3, characterized in that The insulating antireflection layer includes at least one selected from the group consisting of Hf oxide, Zr oxide, Si oxide, Al oxide, and Mg fluoride.

6. The light emitting element according to claim 2, characterized in that The p-side transparent electrode is formed to be thinner than the insulating antireflection layer.

7. The light emitting element according to claim 2, characterized in that The thickness of the p-side transparent electrode is less than 20 nm.

8. The light emitting element according to claim 7, characterized in that The insulating antireflection layer has a thickness of 1 nm to 300 nm.

9. The light emitting element according to any one of claims 1 to 3, characterized in that The p-type layer is GaN or AlGaN.

10. An insulating antireflection layer, characterized in that: A light-emitting element for face-up ultraviolet light emission, provided on a p-type layer, comprising at least one selected from the group consisting of Hf oxide, Zr oxide, Si oxide, Al oxide, and Mg fluoride, and preventing reflection of ultraviolet light of emission wavelength.

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