Semiconductor light-emitting element and manufacturing method for semiconductor light-emitting element

Abstract

To provide a semiconductor light-emitting element including a reflection electrode that can suppress corrosion between an ITO layer and an aluminum layer while having high reflectance.SOLUTION: A semiconductor light-emitting element 1 includes: a semiconductor structure 10 including a multilayer structure in which an n-type semiconductor layer 12, an active layer 13, and a p-type semiconductor layer 15 are stacked in order, and a pair of planes facing each other in a stacking direction, which are formed by the n-type semiconductor layer and the p-type semiconductor layer; a light-transmitting substrate 11 provided on one plane of the semiconductor structure, a first ITO layer 21 formed on the other plane of the semiconductor structure, an aluminum layer 22 formed on the first ITO layer, and a second ITO layer 23 formed on the aluminum layer. The aluminum layer is sealed by the first ITO layer and the second ITO layer, or the first ITO layer, the other plane of the semiconductor structure, and the second ITO layer.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a semiconductor light-emitting device and a method for manufacturing the semiconductor light-emitting device. [Background technology]

[0002] Semiconductor light-emitting elements are used as various light sources because they have excellent properties such as being small, emitting light with good power efficiency, having a long life, excellent initial driving characteristics, and being resistant to vibration and repeated on-off lighting.

[0003] In GaN-based light-emitting devices, a reflective electrode is used that combines a transparent electrode such as ITO with a dielectric reflective film. Recently, research has been conducted into structures that can increase the output efficiency, and a structure that combines ITO with a metal reflective layer has been proposed to improve reflectivity.

[0004] For example, Patent Document 1 discloses a nitride semiconductor light-emitting element having a reflective electrode structure composed of a light-transmitting conductive layer made of ITO, a metal reflective layer made of aluminum, and a multi-layered dielectric film, with the aim of improving light extraction efficiency. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2014-044971 A Summary of the Invention [Problem to be solved by the invention]

[0006] When a laminated structure of ITO and aluminum is immersed in an alkaline solution, a local cell is formed between the aluminum / alkaline solution / ITO, dissolution of the aluminum occurs, and a reduction reaction of the ITO occurs, resulting in corrosion of both the ITO and aluminum. In a pattern exposure process using a photoresist, it is necessary to use an alkaline solution as a developer, so if patterning is performed by the pattern exposure process after forming an electrode made of laminated ITO and aluminum, there is a problem that the electrode is corroded by the developer in the development step.

[0007] To address the above-mentioned problems, in Patent Document 1, a metal barrier layer made of a group consisting of Au, Ag, Pt, Pd, Rh, Ir, Ru, and Os is provided between a translucent conductive layer made of ITO and a metal reflective layer made of aluminum to prevent corrosion.

[0008] However, when a metal barrier layer is provided between the ITO layer and the aluminum layer as described above, there is a problem that the reflectance of the reflective electrode decreases due to light absorption in the metal barrier layer. Furthermore, there is a problem that alloying and interdiffusion between aluminum and the metal barrier layer occurs due to the thermal load generated during the processing of the semiconductor light-emitting element and the heat generated during use of the semiconductor light-emitting element, resulting in a decrease in reflectance and an increase in electrical resistance.

[0009] Therefore, an object of the present invention is to provide a semiconductor light-emitting element having a reflective electrode that has high reflectivity without using a metal barrier layer and can suppress corrosion of the ITO layer and the aluminum layer, and a manufacturing method thereof. [Means for solving the problem]

[0010] A semiconductor light-emitting element according to one embodiment of the present invention is a semiconductor light-emitting element comprising: a stacked structure in which an n-type semiconductor layer, an active layer, and a p-type semiconductor layer are stacked in this order; a semiconductor structure having a pair of planes facing each other in the stacking direction formed by the n-type semiconductor layer and the p-type semiconductor layer; a light-transmitting substrate provided on one plane of the semiconductor structure; a first ITO layer formed on the other plane of the semiconductor structure; an aluminum layer formed on the first ITO layer; and a second ITO layer formed on the aluminum layer, wherein the aluminum layer is sealed by the first ITO layer and the second ITO layer, or by the first ITO layer, the other plane of the semiconductor structure, and the second ITO layer.

[0011] Furthermore, a method for manufacturing a semiconductor light-emitting element according to one embodiment of the present invention is a method for manufacturing a semiconductor light-emitting element comprising a semiconductor structure having a stacked structure in which an n-type semiconductor layer, an active layer, and a p-type semiconductor layer are stacked in this order, and a pair of planes facing each other in the stacking direction formed by the n-type semiconductor layer and the p-type semiconductor layer, the method including the steps of forming a first ITO layer on one plane of the semiconductor structure, forming an aluminum layer on the first ITO layer, and forming a second ITO layer on the aluminum layer, and the aluminum layer is sealed by the first ITO layer and the second ITO layer, or the first ITO layer, the other plane of the semiconductor structure, and the second ITO layer. [Brief description of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view illustrating a schematic structure of a semiconductor light-emitting device according to one embodiment of the present invention. [Diagram 2] FIG. 1 is a flow diagram showing steps of a method for manufacturing a semiconductor light-emitting device according to one embodiment of the present invention. [Diagram 3] FIG. 2 is a cross-sectional view showing a schematic structure of Comparative Example 1 having no second ITO layer, Comparative Example 2 having no side surface of the aluminum layer, and Example 1 having a second ITO layer. [Figure 4]FIG. 1 shows the state of corrosion when Comparative Example 1 having no second ITO layer, Comparative Example 2 having no covering of the side surface of the aluminum layer, and Example 1 having a second ITO layer are immersed in an alkaline solution. [Diagram 5] 1 is a graph showing reflectance versus the type of metal layer and the presence or absence of a metal layer. [Figure 6] 1 is a graph showing reflectance versus thickness of a first ITO layer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] In the following, preferred embodiments of the present invention will be described, which may be modified and combined as appropriate. In the following description and accompanying drawings, substantially the same or equivalent parts are designated by the same reference numerals.

[0014] [Structure of semiconductor light-emitting element] 1 is a cross-sectional view showing a schematic structure of a semiconductor light-emitting element 1 according to one embodiment of the present invention. The semiconductor light-emitting element 1 is a deep ultraviolet light-emitting diode (deep ultraviolet LED), and has a semiconductor structure 10, a substrate 11, and a reflective electrode structure 20. The semiconductor structure 10 is formed by epitaxially growing an n-type cladding layer 12, an active layer 13, an electron blocking layer 14, a p-type cladding layer 15, and a p-type contact layer 16 on the substrate 11 in that order.

[0015] Here, the deep ultraviolet LED is a semiconductor light emitting element that emits light in the deep ultraviolet region (approximately 200 nm to 300 nm) and has been attracting attention in recent years as a light source that has an inactivating effect and a sterilizing effect on bacteria and viruses.

[0016] The substrate 11 is a light-transmitting substrate on which the semiconductor structure 10 can be epitaxially grown, and the size, thickness, etc. of the substrate are not particularly limited. For example, an AlN template substrate in which an AlN film is laminated on a sapphire substrate, or a single crystal AlN substrate can be used.

[0017] In addition, if the absorption coefficient of the substrate for the deep ultraviolet light emitted from the active layer 13 is large, the total amount of deep ultraviolet light that can be extracted to the outside is reduced, which may lead to a decrease in the light emission efficiency. Therefore, the absorption coefficient of the substrate is preferably 20 cm -1 Less than 10 cm, more preferably -1 The following is the result.

[0018] The n-type cladding layer 12 is an n-type semiconductor layer doped with Si (silicon). The n-type cladding layer 12 is, for example, AlGaN, and the Al composition can be appropriately determined so as to obtain sufficient transparency for the desired emission wavelength of ultraviolet light.

[0019] The n-type cladding layer 12 may be formed of multiple layers having different Al compositions, and may be a compositionally graded layer in which the Al composition is graded in the stacking direction. For example, the n-type cladding layer 12 in FIG. X1 Ga 1-X1 The first n-type cladding layer 12A is made of N and the second n-type cladding layer 12B is made of Al X2 Ga 1-X2 The second n-type cladding layer 12B is made of AlN. X1 Ga 1-X1 The first n-type cladding layer 12A made of N is a composition gradient layer in which the Al composition X1 decreases from 1.0 to 0.75 in the stacking direction. X2 Ga 1-X2 The second n-type cladding layer 12B made of N may be a compositionally graded layer in which the Al composition X2 decreases from 0.75 to 0.70.

[0020] The Si concentration to be doped into the n-type cladding layer 12 may be appropriately determined so as to obtain a desired n-type conductivity. The Si doping concentration may be constant in the thickness direction of the n-type cladding layer 12, or it may be modulated so that the Si concentration varies in the thickness direction.

[0021] The active layer (ACT) 13 is, for example, Al A1 Ga 1-A1 A barrier layer made of N layers and Al A2 Ga 1-A2The active layer 13 has a quantum well structure composed of a well layer made of N layers. The emission peak wavelength of the active layer 13 is in the range of 200 to 300 nm. Since the wavelength of the light emitted from the active layer 13 is determined by the Al composition and film thickness of the well layer, the Al composition and film thickness can be appropriately determined so as to obtain a desired emission wavelength in the above wavelength range.

[0022] The well layer and barrier layer may be n-type layers doped with Si. Both the well layer and the barrier layer may be Si-doped layers, or only the well layer or only the barrier layer may be doped with Si. The number of quantum well layers is not particularly limited, and may be a multi-quantum well (MQW) structure in which multiple well layers are formed, or a single quantum well (SQW). The number of well layers is preferably determined appropriately within the range of 1 to 5.

[0023] The electron blocking layer 14 is a layer provided adjacent to the active layer 13. The electron blocking layer 14 is made of, for example, AlN, and has a function of suppressing the overflow of electrons injected into the active layer 13 into the p-type cladding layer 15. Therefore, the electron blocking layer 14 has a larger band gap than the active layer 13 and the p-type cladding layer 15 described later.

[0024] In addition, the electron blocking layer 14 may be an undoped layer or may be doped with a p-type dopant as long as it can function as an electron blocking layer. Examples of p-type dopant materials that can be used in the electron blocking layer 14 include Mg (magnesium), Zn (zinc), Be (beryllium), and C (carbon).

[0025] The p-type cladding layer 15 is, for example, AlGaN, and is a p-type semiconductor layer co-doped with a p-type impurity acting as an acceptor and an n-type impurity acting as a donor. The p-type impurity may be Mg (magnesium), Zn (zinc), Be (beryllium), C (carbon), or the like. Of these, it is preferable to use Mg, which is generally used as a p-type dopant material for AlGaN semiconductors. The n-type impurity may be Si, Ge (germanium), Se (selenium), S (sulfur), O (oxygen), or the like. Of these, it is preferable to use Si, which is generally used as an n-type dopant material.

[0026] The amounts of p-type impurities and n-type impurities doped into the p-type cladding layer 15 may be appropriately determined so as to obtain a desired p-type conductivity. The concentrations of the p-type impurities and n-type impurities doped into the p-type cladding layer 15 may be constant within the layer, or may vary in the stacking direction.

[0027] The Al composition of the p-type cladding layer 15 can be determined appropriately, and may be a constant value in the stacking direction, or may be a compositionally graded layer that changes in the stacking direction.

[0028] The p-type contact layer 16 is a GaN layer doped with a p-type dopant and has the function of reducing the contact resistance with the electrode. As the p-type dopant material, the above-mentioned known p-type dopant materials can be used, but for the same reason, it is preferable to use Mg.

[0029] The thicknesses of the n-type cladding layer 12, active layer 13, electron blocking layer 14, p-type cladding layer 15, and p-type contact layer 16 are not particularly limited and can be set appropriately. In order to improve the reflectance of the semiconductor light emitting element 1, it is preferable that the thickness of the p-type contact layer 16 is as thin as possible. It is also preferable that the total thickness of the p-type contact layer 16 and the first ITO layer 21 described below is as thin as possible.

[0030] As shown in FIG. 1, the reflective electrode structure 20 of the present invention is formed on the p-type contact layer 16, which is one of the planes in the stacking direction of the semiconductor structure 10, and is composed of a first ITO layer 21, an aluminum layer 22, and a second ITO layer 23.

[0031] The first ITO layer 21 is a light-transmitting conductive layer made of ITO (indium tin oxide), and is in contact with the p-type contact layer 16 to provide good ohmic contact.

[0032] The thickness of the first ITO layer 21 can be appropriately selected taking into consideration the light absorption and electrical resistance, but here, when a deep ultraviolet semiconductor light emitting element is used as the semiconductor light emitting element 1, the light absorption of ITO is large in the deep ultraviolet region, so the thickness of the first ITO layer 21 is preferably thinner, more preferably 1 nm to 15 nm, even more preferably 1 nm to 7 nm, and most preferably 2 nm to 4 nm. If the thickness of the first ITO layer 21 is less than 1 nm, it is difficult to form the layer in the manufacturing process, and if the thickness of the first ITO layer 21 is more than 15 nm, the light absorption is large in the deep ultraviolet region, and the extraction efficiency of the semiconductor light emitting element 1 is reduced.

[0033] The first ITO layer 21 can be formed by a known method such as sputtering or electron beam evaporation, but in order to increase the transparency of the ITO after formation, it is preferable to use the sputtering method.

[0034] The sputtering method involves placing a target (film material) used to form a thin film in a vacuum chamber, applying high voltage to ionize rare gas (mainly argon) and colliding it with the target, scattering atoms on the target surface and forming a high-density film of the film material on the substrate. In addition, by introducing reactive gases (oxygen and nitrogen) together with the rare gas, metal oxides and metal nitrides can also be formed.

[0035] As the sputtering method applicable to the present invention, known sputtering methods such as two-pole sputtering, magnetron sputtering, DC sputtering, DC pulse sputtering, RF (radio frequency) sputtering, dual magnetron sputtering, reactive sputtering, ion beam sputtering, bias sputtering, and facing target sputtering can be appropriately used.

[0036] The aluminum layer 22 is made of aluminum or an alloy thereof, and functions as an electrode by being electrically connected to the p-type contact layer 16 via the first ITO layer 21. The aluminum layer 22 also functions as a reflective layer that reflects light from the active layer 13, thereby improving the extraction efficiency of the semiconductor light emitting element 1.

[0037] Aluminum has a higher reflectance than other metals such as Au, Ag, Pt, Pd, Rh, Ir, Ru, and Os, and therefore can be suitably used as the reflective layer described above.

[0038] The aluminum layer 22 can be formed by a known method such as sputtering or vacuum deposition. In order to form the aluminum layer more simply, it is preferable to use the vacuum deposition method.

[0039] The vacuum deposition method is a method in which the material to be deposited is heated in a vacuum chamber to melt and vaporize it, and the vaporized material is deposited on the surface of the substrate. The vacuum deposition method has the advantage that it can form a layer with fewer impurities because the material can be easily vaporized by using a vacuum chamber and the impact of collisions with residual gases such as air and steam can be reduced.

[0040] The thickness of the aluminum layer 22 may be any thickness that can effectively reflect light from the active layer 13, and may be selected, for example, in the range of 200 nm or less.

[0041] The second ITO layer 23 is a cover layer that covers the aluminum layer 22, and is formed so as to cover a surface (hereinafter referred to as an upper surface) of the aluminum layer 22 that faces a surface (hereinafter referred to as a lower surface) that abuts against the first ITO layer 21, and a surface (hereinafter referred to as a side surface) that connects the lower surface and the upper surface. As a result, the aluminum layer 22 is sealed by two layers, the second ITO layer 23 and the first ITO layer 21, or by three layers including the p-type contact layer 16. By sealing the aluminum layer 22 as described above, it is possible to prevent the aluminum layer 22 from coming into contact with an alkaline solution when immersed in the alkaline solution, and corrosion can be suppressed.

[0042] Here, when the aluminum layer 22 has its entire lower surface in contact with the first ITO layer 21, it is sealed by the second ITO layer 23 and the first ITO layer 21, and when a portion of its lower surface is not in contact with the first ITO layer 21, it is sealed by the second ITO layer 23, the first ITO layer 21, and the p-type contact layer 16. However, in order to more reliably suppress corrosion of the aluminum layer 22, it is preferable that its entire lower surface is in contact with the first ITO layer 21 and is sealed by the second ITO layer 23 and the first ITO layer 21.

[0043] The second ITO layer 23 can be formed by known methods such as sputtering and electron beam deposition, but it is preferable to use the sputtering method because it can simultaneously cover the side surfaces of the aluminum layer 22. If it is not possible to cover not only the top surface but also the side surfaces of the aluminum layer 22, it is not possible to prevent the aluminum layer 22 from coming into contact with an alkaline solution, and therefore it is not possible to obtain the effect of suppressing corrosion.

[0044] In order to more simply obtain a structure in which the aluminum layer 22 is sealed, it is preferable to form the first ITO layer 21 by sputtering, the aluminum layer 22 by vacuum deposition, and the second ITO layer 23 by sputtering.

[0045] In order to more reliably suppress corrosion of the aluminum layer 22, it is preferable that the first ITO layer 21 encompasses the aluminum layer 22 when viewed from the stacking direction of the semiconductor structure 10, and is sealed by the aluminum layer 22, the second ITO layer 23, and the p-type contact layer 16.

[0046] When viewed from the stacking direction of the semiconductor structure 10, if the first ITO layer 21 is formed smaller than the aluminum layer 22 or if the first ITO layer 21 and the aluminum layer 22 are formed out of alignment, and the first ITO layer 21 does not include the aluminum layer 22, the lower surface of the aluminum layer 22 will be partially uncovered. If the second ITO layer 23 is formed continuously in this state, gaps will be formed around the aluminum layer 22, and the alkaline solution may seep into the periphery of the aluminum layer 22 through the gaps.

[0047] When viewed from the stacking direction of the semiconductor structure 10, the first ITO layer 21 encompasses the aluminum layer 22, so that the entire lower surface of the aluminum layer 22 abuts against the first ITO layer 21, and the aluminum layer 22 is sealed by the first ITO layer 21 and the second ITO layer 23. As a result, the aluminum layer 22 is completely covered with no gaps, so corrosion can be more reliably suppressed.

[0048] Furthermore, if the first ITO layer 21 is not sealed by the aluminum layer 22, the second ITO layer 23, and the p-type contact layer 16, the interface between the first ITO layer 21 and the second ITO layer 23 is formed from the periphery of the aluminum layer 22 to the outside of the second ITO layer 23, and there is a possibility that an alkaline solution will seep into the periphery of the aluminum layer 22 through the gaps at the interface. Since the first ITO layer 21 is sealed by the aluminum layer 22, the second ITO layer 23, and the p-type contact layer 16, the interface between the first ITO layer 21 and the second ITO layer 23 is blocked by the p-type contact layer 16, and therefore corrosion can be more reliably suppressed.

[0049] The thickness of the second ITO layer 23 is not particularly limited as long as it is thick enough to cover the aluminum layer 22, and is, for example, 300 nm to 1000 nm.

[0050] It is preferable that after forming the first ITO layer 21, the aluminum layer 22, and the second ITO layer 23, they are subjected to a heat treatment to establish an ohmic contact with the p-type contact layer 16. The heat treatment is not particularly limited, but can be performed, for example, by maintaining the temperature at 200 to 600° C. for 1 to 15 minutes. The timing of the heat treatment is not limited to the above, and after forming the first ITO layer 21, an ohmic contact may be established with the p-type contact layer 16 by subjecting the layer to a heat treatment, and then the aluminum layer 22 and the second ITO layer 23 may be formed.

[0051] Although the reflective electrode structure 20 of the present invention has been described as a p-type electrode formed on the p-type contact layer 16, it can also be used as an n-type electrode. The n-type electrode can be formed on the second n-type clad layer 12B by forming a mask having a predetermined shape on the surface (p-type contact layer 16 side) of the semiconductor structure 10 in a portion not shown in Fig. 1, and etching the active layer 13, the electron blocking layer 14, the p-type clad layer 15, and the p-type contact layer 16 until the second n-type clad layer 12B is exposed.

[0052] Although the semiconductor light emitting element 1 has been described as being a light emitting diode (LED), it may also be configured as a semiconductor laser element (LD: Laser Diode).

[0053] [Method of manufacturing semiconductor light-emitting device] Next, a method for manufacturing the semiconductor light-emitting device 1 according to an embodiment of the present invention will be described. Fig. 2 is a flow chart showing an example of the procedure of the method for manufacturing the semiconductor light-emitting device 1 according to an embodiment of the present invention. The method for manufacturing the semiconductor light-emitting device 1 according to an embodiment of the present invention includes a step (STEP 1) of forming a semiconductor structure 10 on a substrate, a step (STEP 2) of forming a first ITO layer 21 on the semiconductor structure 10, a step (STEP 3) of forming an aluminum layer 22 on the first ITO layer 21, a step (STEP 4) of forming a second ITO layer 23 on the aluminum layer 22, and a heat treatment step (STEP 5). Although not shown in Fig. 2, a step of heat treatment may be added between STEP 2 and STEP 3.

[0054] The step of forming semiconductor structure 10 on a substrate (STEP 1) is, as described above, a step of forming an n-type cladding layer 12, an active layer 13, an electron blocking layer 14, a p-type cladding layer 15 and a p-type contact layer 16 on a substrate 11 by epitaxial growth.

[0055] The step (STEP 2) of forming the first ITO layer 21 on the semiconductor structure 10 is a step of forming the first ITO layer 21 on the p-type contact layer 16, which is one of the planes in the stacking direction of the semiconductor structure 10. The method of forming the first ITO layer 21 can be selected from well-known methods such as sputtering and electron beam deposition, but sputtering is preferable.

[0056] The step (STEP 3) of forming the aluminum layer 22 on the first ITO layer 21 can be performed by a method selected from known methods such as sputtering, vapor deposition, etc. As described above, the aluminum layer 22 is preferably formed so as to be included in the first ITO layer 21 when viewed from the stacking direction of the semiconductor structure 10.

[0057] The step (STEP 4) of forming the second ITO layer 23 on the aluminum layer 22 is a step of forming the second ITO layer 23 so as to cover the upper surface and side surfaces of the aluminum layer 22, and in order to cover the side surfaces at once, it is preferable to perform this by a sputtering method.

[0058] By forming the second ITO layer 23 to cover the upper and side surfaces of the aluminum layer 22, the aluminum layer 22 is sealed by the first ITO layer 21 and the second ITO layer 23, or the first ITO layer 21, the p-type contact layer 16, and the second ITO layer.

[0059] The heat treatment step (STEP 5) is a step of performing heat treatment to establish ohmic contact between the reflective electrode structure 20 consisting of the first ITO layer 21, the aluminum layer 22, and the second ITO layer and the p-type contact layer 16, and can be performed, for example, by maintaining the temperature at 200 to 600°C for 1 to 15 minutes.

[0060] Through the above steps, the semiconductor light emitting device 1 shown in Fig. 1 is obtained. The manufacturing method of the present invention only needs to include the above steps 1 to 5, and other steps may be performed before, after, or between the steps as necessary. For example, a step of exposing the second n-type cladding layer 12B by etching, or a step of dividing the semiconductor light emitting devices 1 into individual devices when multiple semiconductor light emitting devices 1 are formed on one substrate 11 may be performed. EXAMPLES

[0061] [Test 1. Corrosion inhibition] (1) Fabrication of semiconductor structures As a semiconductor structure for a deep-ultraviolet semiconductor light-emitting element (deep-ultraviolet LED), a first n-type cladding layer (200 nm), a second n-type cladding layer (1000 nm), and an active layer (40 nm) made of AlGaN, an electron blocking layer (9 nm) made of AlN, a p-type cladding layer (60 nm) made of AlGaN, and a p-type contact layer (270 nm) made of GaN were sequentially grown on an AlN single crystal substrate prepared by the method described in Applied Physics Express 5 (2012) 122101 using an MOCVD apparatus.

[0062] The first n-type cladding layer and the second n-type cladding layer are both compositionally graded layers, and in the first n-type cladding layer, the Al composition decreases from 1.0 to 0.75 from the side in contact with the AlN layer, and in the second n-type cladding layer, the Al composition decreases from 0.75 to 0.70 from the side in contact with the first n-type cladding layer.

[0063] The p-type cladding layer is a compositionally graded layer in which the Al composition decreases from 0.98 to 0.8 from the side in contact with the electron blocking layer.

[0064] (2) Preparation of electrodes A first ITO layer was formed to a thickness of 4 nm on the p-type contact layer of the obtained deep ultraviolet semiconductor light-emitting device by a sputtering method, and an aluminum layer was further formed to a thickness of 100 nm on the first ITO layer by a vacuum deposition method. Without forming a second ITO layer, the electrode was produced by heat treatment at 450°C in an oxygen atmosphere, and the semiconductor light-emitting device of Comparative Example 1 was obtained. The structure of the electrode of Comparative Example 1 is shown in FIG. 3A.

[0065] Furthermore, an electrode was prepared in the same manner as in Comparative Example 1, except that a barrier layer made of titanium was formed to a thickness of 300 nm on the first ITO layer by electron beam deposition prior to the heat treatment, to produce a semiconductor light-emitting device of Comparative Example 2. The structure of the electrode of Comparative Example 2 is shown in FIG. 3B. As shown in FIG. 3B, the barrier layer covers only the top surface of the aluminum layer, and does not cover the side surfaces.

[0066] Furthermore, an electrode was prepared in the same manner as in Comparative Example 1, except that a second ITO layer was formed to a thickness of 300 nm on the first ITO layer by sputtering prior to the heat treatment, to produce a semiconductor light-emitting device of Example 1. The structure of the electrode of Example 1 is shown in FIG. 3C. Here, as shown in FIG. 3C, the second ITO layer covers the upper and side surfaces of the aluminum layer and the first ITO layer.

[0067] (3) Electrode corrosion evaluation The semiconductor light-emitting devices of Comparative Examples 1 and 2 and Example 1 described above were immersed in an alkaline solution (AZ600MIF) for 100 seconds, removed, and the shape of the electrodes was observed under a microscope. The results of Comparative Example 1 are shown in FIG. 4A, the results of Comparative Example 2 in FIG. 4B, and the results of Example 1 in FIG. 4C.

[0068] As shown in Figure 4, in Comparative Example 1, which does not have a second ITO layer, and Comparative Example 2, in which a titanium layer is formed on an aluminum layer, the shape of the aluminum layer could not be clearly confirmed, and it was found that there was corrosion. In contrast, in Example 1, in which the first ITO layer and the aluminum layer are covered with a second ITO layer, the shape of the aluminum layer could be clearly confirmed, and it was confirmed that there was no corrosion of the aluminum layer.

[0069] [Test 2. Reflectance with and without metal barrier layer] A 5 nm thick metal layer of nickel or rhodium was formed on an aluminum plate, and the reflectance was simulated (Essential Macleod (Thin Film Center Inc.)) when light of various wavelengths was vertically incident on the aluminum plate from the side with the metal layer. The reflectance was also simulated in the same way when light was vertically incident on an aluminum plate without a metal layer. The results are shown in Figure 5.

[0070] Fig. 5 is a graph showing the change in reflectance between the case where a nickel or rhodium metal layer is present and the case where no metal layer is present, with the horizontal axis representing the wavelength of light incident perpendicularly and the vertical axis representing the reflectance. As shown in Fig. 5, it was found that in the region where the wavelength of light is 300 nm or less, the reflectance is greatly reduced when a nickel or rhodium metal layer is present. In contrast, it was found that in the case where there is no metal layer and only aluminum is present, the reflectance does not decrease even in the wavelength region of 300 nm or less. This is because the reflectance of nickel and rhodium is lower than that of aluminum.

[0071] When using a deep ultraviolet semiconductor light emitting element, since the wavelength of the output light is about 200 nm to 300 nm, it was confirmed that it is preferable not to have a metal layer such as nickel or rhodium from the result of Fig. 5. From this, it was found that the semiconductor light emitting element of this embodiment, which can form a reflective electrode without using a metal barrier layer, has a higher reflectance.

[0072] [Test 3. Reflectance as a function of film thickness] An ITO layer and an aluminum layer were formed on a sapphire substrate, incident light was irradiated from the sapphire substrate side, the spectrum of the reflected light was measured, and the reflectance was calculated from the ratio to the incident light. This was done while changing the thickness of the ITO layer and the wavelength of the incident light. The reflected light spectrum was measured using an n&k analyzer (n&k Technology, Inc.).

[0073] Figure 6 is a graph showing the change in reflectance depending on the ITO film thickness, with the horizontal axis representing the wavelength of incident light and the vertical axis representing the reflectance. As shown in Figure 6, it was found that the reflectance of ITO drops significantly when the wavelength of incident light is 350 nm or less. This is due to the light absorption of ITO.

[0074] When using a deep ultraviolet semiconductor light emitting element, the wavelength of the output light is about 200 nm to 300 nm, so it is required that the reflectance does not decrease even in the wavelength region of 350 nm or less. Looking at Figure 6, it was found that when the ITO film thickness is 15 nm or less, the reflectance at a wavelength of 350 nm is 70% or more, and the decrease in reflectance is small even in the wavelength region of 350 nm or less. From this, it is possible to obtain a higher reflectance when the thickness of the first ITO layer is 1 nm to 15 nm.

[0075] In addition, when the ITO film thickness is 7nm or less, the reflectance at a wavelength of 350nm is 77% or more, and the decrease in reflectance is smaller even in the wavelength region of 350nm or less, when the ITO film thickness is 4nm or less, the reflectance at a wavelength of 350nm is 80% or more, and the decrease in reflectance is even smaller even in the wavelength region of 350nm or less, and when the ITO film thickness is 2nm or less, the reflectance at a wavelength of 350nm is 86% or more, and the decrease in reflectance is particularly small even in the wavelength region of 350nm or less. For ITO film thicknesses of 1nm or less, the reflectance is not lower than when the ITO film thickness is 2nm, and it is difficult to form a layer, so it is not displayed.

[0076] This shows that the reflectance is greater than when the thickness of the first ITO layer is 15 nm, and the decrease in reflectance is smaller even in the wavelength region of 350 nm or less, so that the thickness of the first ITO layer is more preferably 1 nm to 7 nm, and most preferably 2 nm to 4 nm.

[0077] As described above in detail, according to this embodiment, it is possible to provide a semiconductor light-emitting element having a reflective electrode that has high reflectivity and can suppress corrosion of the ITO layer and the aluminum layer. [Explanation of symbols]

[0078] 1: semiconductor light emitting element, 10: semiconductor structure, 11: substrate, 12: n-type cladding layer, 12A: first n-type cladding layer, 12B: second n-type cladding layer, 13: active layer, 14: electron blocking layer, 15: p-type cladding layer, 16: p-type contact layer, 20: reflective electrode structure, 21: first ITO layer, 22: aluminum layer, 23: second ITO layer

Claims

1. a semiconductor structure having a stacked structure in which an n-type semiconductor layer, an active layer, and a p-type semiconductor layer are stacked in this order, and a pair of planes formed by the n-type semiconductor layer and the p-type semiconductor layer and facing each other in the stacking direction; a light-transmitting substrate provided on one surface of the semiconductor structure; a first ITO layer formed on the other planar surface of the semiconductor structure; an aluminum layer formed on the first ITO layer; a second ITO layer formed on the aluminum layer, A semiconductor light-emitting element, characterized in that the aluminum layer is sealed by the first ITO layer and the second ITO layer, or by the first ITO layer, the other plane of the semiconductor structure, and the second ITO layer.

2. 2. The semiconductor light emitting element according to claim 1, wherein the first ITO layer has a thickness of 1 nm to 15 nm.

3. 2. The semiconductor light-emitting element according to claim 1, wherein the first ITO layer encompasses the aluminum layer when viewed from the stacking direction, and is sealed by the aluminum layer, the second ITO layer, and the p-type semiconductor layer.

4. 1. A method for manufacturing a semiconductor light-emitting device comprising a semiconductor structure having a stacked structure in which an n-type semiconductor layer, an active layer, and a p-type semiconductor layer are stacked in this order, and a pair of planes formed by the n-type semiconductor layer and the p-type semiconductor layer and facing each other in the stacking direction, comprising: forming a first ITO layer on one planar surface of the semiconductor structure; forming an aluminum layer on the first ITO layer; forming a second ITO layer on the aluminum layer; a second ITO layer formed on the first ITO layer and a second ITO layer formed on the second ITO layer;

5. 5. The method for producing a semiconductor light emitting device according to claim 4, wherein the second ITO layer is formed by a sputtering method.

6. The first ITO layer is formed by a sputtering method; 6. The method for producing a semiconductor light-emitting device according to claim 5, wherein the aluminum layer is formed by a vacuum deposition method.

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