Method for manufacturing a light-emitting element and a light-emitting element

Abstract

The present invention provides a method for producing a light emitting element which is composed of a GaN semiconductor, the method comprising: a step in which a light emitting layer 12 that has a quantum well structure is formed on a substrate 10; a step in which a cap layer 13 that is formed of GaN is formed on the light emitting layer; and a step in which an oxide film 14 is formed on the cap layer. With respect to this method for producing a light emitting element, the oxide film is formed of an oxide of an element which can be diffused and infiltrated into Ga vacancies that are present within the cap layer that is configured from GaN.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a light-emitting device made of a GaN-based semiconductor and a light-emitting device.

Background Art

[0002] As a light-emitting device such as a light-emitting diode made of a GaN-based semiconductor, a light-emitting device including a light-emitting layer composed of InGa N and having a quantum well structure is known.

[0003] InGaN is a mixed crystal of GaN and InN, and by adjusting its composition ratio, the bandgap energy can be changed, and thereby the emission wavelength can be controlled. However, in the blue region, high luminous efficiency has been achieved, but in other regions, the current situation is that the luminous efficiency is extremely low.

[0004] As an approach for improving the luminous efficiency, a method using surface plasmon resonance has been proposed (Non-Patent Document 1). In this method, a metal thin film is formed near the InGaN light-emitting layer with a GaN layer (cap layer) interposed therebetween. When electron-hole pairs generated in the InGaN light-emitting layer emit light by recombination, they resonate with surface plasmons generated at the interface between the metal thin film and the GaN layer, thereby increasing the emission speed and improving the luminous efficiency.

Prior Art Documents

Non-Patent Documents

[0005]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Methods utilizing surface plasmon resonance suffer from significant light loss because light from the light-emitting layer is absorbed by a thin metal film, and there is also the problem of the lack of suitable metal materials for the green region.

[0007] The present invention has been made in view of the above, and aims to provide a method for manufacturing a light-emitting element and a light-emitting element that can improve the luminous efficiency of a light-emitting element composed of a GaN-based semiconductor. [Means for solving the problem]

[0008] The present invention relates to a method for manufacturing a light-emitting element composed of a GaN-based semiconductor, comprising the steps of: forming a light-emitting layer having a quantum well structure on a substrate; forming a cap layer made of GaN on the light-emitting layer; and forming an oxide film on the cap layer, wherein the oxide film consists of an oxide of an element that can diffusely penetrate into Ga vacancies present in the cap layer made of GaN.

[0009] The light-emitting element according to the present invention is a light-emitting element composed of a GaN-based semiconductor, comprising a light-emitting layer having a quantum well structure, a cap layer made of GaN formed on the light-emitting layer, and a ZnO film formed on the cap layer. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a method for manufacturing a light-emitting element that can improve the luminous efficiency of a light-emitting element composed of a GaN-based semiconductor, and a light-emitting element itself. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic cross-sectional view showing the structure of a sample prepared to illustrate the present invention. [Figure 2] This graph shows the results of measuring photoluminescence (PL) in a sample in which an SiO2 film was formed on a GaN layer (cap layer) after irradiation with excitation light. [Figure 3]This graph shows the temperature dependence of the emission intensity measured for a sample that emits yellow-green light. [Figure 4] This graph shows the results of measuring the change in emission intensity when the laser irradiation time was varied for a sample that emits yellow-green light. [Figure 5] This graph plots the emission intensity against the laser irradiation time. [Figure 6] This graph shows the results of measuring photoluminescence (PL) on a sample after the SiO2 film surface was irradiated with a laser and then the SiO2 film was removed. [Figure 7] This graph shows the results of measuring photoluminescence (PL) in a sample in which a ZnO film was formed on a GaN layer (cap layer) after irradiation with excitation light. [Figure 8] This graph shows the results of measuring the change in emission intensity when the laser irradiation time is varied. [Figure 9] This graph plots the emission intensity against the laser irradiation time. [Figure 10] This graph shows the time-resolved emission profile measured for a sample in which an SiO2 film was formed on a GaN layer (cap layer). [Figure 11] This graph shows the results of measuring the Si concentration in the GaN layer (cap layer). [Figure 12] Figures (A) to (C) are graphs plotting the emission intensity against the laser irradiation time when the thickness of the GaN layer (cap layer) is changed. [Figure 13] This graph shows the ratio of luminescence intensity when an SiO2 film is formed on the GaN layer (cap layer) and when the SiO2 film 14 is not formed, measured for samples with varying GaN layer (cap layer) thicknesses. [Figure 14] This is a schematic cross-sectional view showing the configuration of the light-emitting element of the present invention. [Figure 15] This is a schematic cross-sectional view showing another configuration of the light-emitting element of the present invention. [Figure 16] This is a cross-sectional view showing a modified example of the light-emitting element of the present invention.

Mode for Carrying Out the Invention

[0012] The inventors of the present application have found a surprising phenomenon that the luminous efficiency is remarkably improved by forming an oxide film made of a specific material on the surface of a GaN layer formed on the surface of an InGaN light-emitting layer, instead of forming a metal thin film.

[0013] (Enhanced Light Emission Using SiO2 Film) FIG. 1 is a cross-sectional view schematically showing the structure of a sample fabricated to verify the above phenomenon.

[0014] As shown in FIG. 1, a GaN layer 11 with a thickness of 3 μm was formed on a sapphire substrate 1 0 above On the GaN layer 11, an InGaN layer (light-emitting layer) 12 having a quantum well structure with a thickness of 3 nm was formed. Further, a GaN layer (cap layer) 13 with a thickness of 10 nm was formed on the InGaN layer 12, and a SiO2 film 14 with a thickness of 5 nm was formed on the GaN layer 13. Further, the surface of the SiO2 film 14 was irradiated with a He-Cd laser (wavelength: 325 nm; intensity: 200 mW) for 10 minutes. In the fabricated sample, the GaN layer 11 and the GaN layer (cap layer) 13 were made non-doped in order to examine the light emission of the sample by photoluminescence (PL) described later. When forming a light-emitting element such as an LED, the GaN layer 11 may be made n-type and the GaN layer (cap layer) 13 may be made p-type.

[0015] Here, the In composition ratio of the InGaN layer (light-emitting layer) 12 was adjusted so that light of blue (470 nm), green (510 nm), and yellow-green (540 nm) would be emitted. Also, the GaN layer 11, the InGaN layer 12, and the GaN layer 13 were each formed using metalorganic vapor phase epitaxy, and the SiO2 film 14 was formed using sputtering.

[0016] Figure 2 is a graph showing the results of measuring photoluminescence (PL) when a sample with an SiO2 film 14 formed on a GaN layer (cap layer) 13 and a sample without an SiO2 film 14 were irradiated with excitation light from a He-Cd laser (wavelength: 325 nm; intensity: 200 mW). Here, the graphs shown by the solid lines A, B, and C represent the samples with the SiO2 film 14 formed, which emitted blue, green, and yellow-green light, respectively. The graphs shown by the dashed lines A', B', and C' represent the samples without the SiO2 film 14 formed, which emitted blue, green, and yellow-green light, respectively.

[0017] As shown in Figure 2, the luminescence intensity of the sample with the SiO2 film 14 formed on it is increased by approximately 1.5 times for the blue-emitting sample, approximately 2.5 times for the green-emitting sample, and approximately 13 times for the yellow-green-emitting sample compared to the sample without the SiO2 film 14 formed on it.

[0018] Figure 3 is a graph showing the temperature dependence of emission intensity for the yellow-green emission sample that showed the greatest increase in emission intensity. Here, the graphs shown with black circles represent samples with the SiO2 film 14 formed, and the graphs shown with black squares represent samples without the SiO2 film 14 formed.

[0019] As shown in Figure 3, the luminescence intensity increases with decreasing temperature and remains constant at extremely low temperatures. This is because, as temperatures decrease, the thermal motion of excitons decreases, making it less likely for excitons to be trapped at non-luminescent sites such as impurities, dislocations, and defects, thus suppressing thermal deactivation that causes a decrease in luminescence efficiency. Therefore, when the luminescence intensity becomes constant at extremely low temperatures, the internal quantum efficiency of the luminescence is considered to be approximately 100%, and by comparing this value, the internal quantum efficiency of the luminescence at each temperature can be estimated. This shows that the internal quantum efficiency was 1.3% in the sample without the SiO2 film 14, while it increased to 22% in the sample with the SiO2 film 14.

[0020] Figure 4 is a graph showing the change in emission intensity when the laser irradiation time is varied for a yellow-green emitting sample. Here, the graphs labeled A0, A1, A2, A3, and A4 show the emission intensity when the laser irradiation time is 0 minutes (no irradiation), 1 minute, 3 minutes, 5 minutes, and 8 minutes, respectively. Note that the graph labeled B is for a sample in which the SiO2 film 14 was not formed. Figure 5 is a graph plotting the emission intensity against the laser irradiation time.

[0021] As shown in Figure 4, the emission intensity increases with increasing laser irradiation time. Furthermore, as shown in Figure 5, the emission intensity saturates after a certain period of laser irradiation. Even without laser irradiation (graph A0), the emission intensity was approximately five times higher compared to the sample without the SiO2 film 14.

[0022] Figure 6 is a graph showing the results of photoluminescence (PL) measurements on samples in which the SiO2 film 14 surface was irradiated with a laser, and then the SiO2 film 14 was removed from the GaN layer (cap layer) 13 using hydrofluoric acid. Here, graph A represents the sample from which the SiO2 film 14 was removed, and graph B represents the sample from which the SiO2 film 14 was not originally formed.

[0023] As shown in Figure 6, it can be seen that even in the sample from which the SiO2 film 14 was removed, a high emission intensity comparable to that of the sample from which the surface of the SiO2 film 14 was laser-irradiated was maintained.

[0024] (Luminescence enhancement using ZnO film) A sample was prepared in which a 5 nm thick ZnO film was formed as the oxide film 14 on the GaN layer (cap layer) 13 instead of the SiO2 film. The ZnO film was formed by sputtering, and the composition was the same as the sample shown in Figure 1, except for the ZnO film. The In composition ratio of the InGaN layer (emissive layer) 12 was adjusted so that it emitted yellow-green light (540 nm). In addition, the surface of the ZnO film was irradiated with a He-Cd laser (wavelength: 325 nm; intensity: 200 mW) for 10 minutes.

[0025] Figure 7 is a graph showing the results of measuring photoluminescence (PL) after irradiating samples with excitation light from a He-Cd laser (wavelength: 325 nm; intensity: 200 mW) with a ZnO film formed on a GaN layer (cap layer) 13, and samples without a ZnO film. Here, the graph labeled A0 represents the sample where laser irradiation was not performed after the ZnO film was formed, the graph labeled A1 represents the sample where laser irradiation was performed after the ZnO film was formed, and the graph labeled B represents the sample where no ZnO film was formed.

[0026] As shown in Figure 7, the emission intensity of the sample that was laser-irradiated after forming a ZnO film was increased by approximately seven times compared to the emission intensity of the sample that was not formed with a ZnO film.

[0027] Figure 8 is a graph showing the change in emission intensity when the laser irradiation time is varied. Here, the graphs labeled A0, A1, A2, and A3 show the emission intensity when the laser irradiation time is 0 minutes (no irradiation), 1 minute, 3 minutes, 5 minutes, and 8 minutes, respectively. Note that the graph labeled B is for a sample in which no ZnO film was formed. Figure 9 is a graph plotting the emission intensity against the laser irradiation time.

[0028] As shown in Figure 8, the emission intensity increases with increasing laser irradiation time. Furthermore, as shown in Figure 9, the emission intensity saturates after a certain period of laser irradiation. Even without laser irradiation (graph A0), the emission intensity is approximately three times higher compared to the sample without a ZnO film.

[0029] Furthermore, even in samples where the ZnO film was removed after laser irradiation, the luminescence intensity remained at a level comparable to that of samples where the ZnO film surface was laser-irradiated.

[0030] From these results, it was found that forming a specific oxide film (SiO2 film or ZnO film) 14 on the GaN layer (cap layer) 13 improves the luminous efficiency, and that irradiating the surface of the oxide film (SiO2 film or ZnO film) 14 with a laser significantly improves the luminous efficiency. Furthermore, it was found that high luminous efficiency is maintained even after removing the oxide film (SiO2 film or ZnO film) 14 after laser irradiation.

[0031] (Mechanism for improving luminous efficiency) The reason why forming an SiO2 or ZnO film on the GaN layer (cap layer) 13 improves the luminous efficiency to a certain extent, and why irradiating the surface of the SiO2 or ZnO film with a laser further significantly improves the luminous efficiency, is not entirely clear, but it is thought that this phenomenon occurs through the following mechanism.

[0032] Figure 10 is a graph showing the time-resolved emission profiles of a sample with an SiO2 film 14 formed on a GaN layer (cap layer) 13 and a sample without an SiO2 film 14. Here, graph A represents the sample with the SiO2 film 14, and graph B represents the sample without the SiO2 film 14.

[0033] As shown in Figure 10, the luminescence lifetime is shorter in the sample with the SiO2 film 14 formed on it, which means that the recombination rate of electron-hole pairs generated in the InGaN layer (luminescent layer) 12 has increased. One possible reason for this increased recombination rate is the improved crystallinity of the GaN layer (cap layer) 13 formed on the InGaN layer (luminescent layer) 12.

[0034] As described above, by forming an SiO2 film or a ZnO film as an oxide film 14 on the GaN layer (cap layer) 13, a certain improvement in luminous efficiency was obtained. Furthermore, by irradiating the surface of the SiO2 film or ZnO film with a laser with a wavelength of 325 nm, a significant improvement in luminous efficiency was obtained. In contrast, when an Al2O3 film was formed as another oxide film on the GaN layer (cap layer) 13, no improvement in luminous efficiency was obtained.

[0035] Normally, Ga vacancies exist in the GaN layer 13, and these Ga vacancies affect the luminescence efficiency of the InGaN layer (emissive layer) 12. However, as shown in Table 1, the covalent bonding radii of Si, Zn, and Al are less than or equal to the covalent bonding radius of Ga. Therefore, Si, Zn, and Al present in the SiO2 film, ZnO film, and Al2O3 film can diffuse into the Ga vacancies present in the GaN layer 13.

[0036] [Table 1]

[0037] On the other hand, a significant improvement in luminous efficiency can be achieved by irradiating with a laser with a wavelength of 325 nm. This wavelength corresponds to an energy of 3.8 eV, which, as shown in Table 2, is higher than the bond energy between Si and O (oxygen) (3.1 eV) and between Zn and O (oxygen) (2.2 eV), and lower than the bond energy between Al and O (oxygen) (5.3 eV).

[0038] [Table 2]

[0039] From this, it is thought that irradiating the surface of the SiO2 film or ZnO film with a laser with a wavelength of 325 nm breaks the bonds between Si or Zn and O, allowing Si or Zn to diffuse into the Ga vacancies present in the crystal of the GaN layer (cap layer) 13, thereby improving the crystallinity of the GaN layer (cap layer) 13. As a result, the internal quantum efficiency of the InGaN layer (emissive layer) 12 is improved, leading to an improvement in luminous efficiency.

[0040] In addition, since the wavelength corresponding to the band gap of GaN is 365 nm, when a laser with a shorter wavelength of 325 nm is irradiated onto the surface of an SiO2 or ZnO film, the light that passes through the SiO2 or ZnO film is absorbed by the GaN layer (cap layer) 13, causing the GaN layer (cap layer) 13 to heat up and its temperature to rise. As a result, the Si or Zn that has diffused from the SiO2 or ZnO film is promoted to diffuse within the crystal of the GaN layer (cap layer) 13, and thus its penetration into the Ga vacancies present in the crystal of the GaN layer (cap layer) 13 is further promoted. As a result, the crystallinity of the GaN layer (cap layer) 13 is further improved, the internal quantum efficiency of the InGaN layer (emissive layer) 12 is improved, and the luminous efficiency is improved.

[0041] To verify the mechanism described above, a SiO2 film (thickness: 5 nm) was formed on a GaN layer (thickness: 10 nm) 13. After irradiating the surface of the SiO2 film with a laser, the elements present in the GaN layer (cap layer) were measured using secondary ion mass spectrometry (SIMS). The measurement was performed after removing the SiO2 film from the GaN layer 13.

[0042] Figure 11 is a graph showing the results, where, from the surface of the GaN layer, in the depth direction, up to 20 nm where the quantum well related to light emission is located, 10 18 ~10 19 atoms / cm 3 It was confirmed that Si was distributed at the specified concentration.

[0043] In contrast, even when the surface of the Al2O3 film is irradiated with a laser with a wavelength of 325 nm, the bond between Al and O does not break. Therefore, the crystallinity of the GaN layer (cap layer) 13 is not improved, and it is thought that no improvement in luminous efficiency was obtained.

[0044] Furthermore, in order to obtain the effect of improving luminescence efficiency by laser irradiation, it is preferable to irradiate the surface of the SiO2 film or ZnO film formed on the GaN layer (cap layer) 13 with a laser having a wavelength with energy greater than the bonding energy between Si or Zn and O (oxygen). In addition, it is preferable to irradiate the surface of the SiO2 film or ZnO film formed on the GaN layer (cap layer) 13 with a laser having a wavelength with energy greater than the bandgap energy of GaN.

[0045] Furthermore, since not only Ga vacancies but also N vacancies exist near the surface of the GaN layer (cap layer) 13, it is conceivable that the crystallinity of the GaN layer (cap layer) 13 may be improved by the diffusion of O, whose bonds with Si and Zn have been broken, into these N vacancies.

[0046] Furthermore, the fact that a certain improvement in luminous efficiency was obtained simply by forming an SiO2 film or a ZnO film on the GaN layer (cap layer) using the sputtering method suggests that when the SiO2 film or ZnO film is formed, a certain number of Si and Zn particles diffuse into the Ga vacancies near the surface of the GaN layer (cap layer) 13 during sputtering, thereby improving the crystallinity of the GaN layer (cap layer) 13.

[0047] Figures 12(A) to (C) are graphs plotting the emission intensity against laser irradiation time when the thickness of the GaN layer (cap layer) 13 is varied in samples in which a 5 nm thick SiO2 film is formed on the GaN layer (cap layer) 13. (A), (B), and (C) are samples with GaN layer (cap layer) 13 thicknesses of 5 nm, 25 nm, and 40 nm, respectively.

[0048] As shown in Figures 12(A) to (C), it can be seen that the time it takes for the luminescence intensity to saturate increases as the thickness of the GaN layer (cap layer) increases. This is thought to be because the time it takes for Si diffused into the GaN layer (cap layer) 13 by laser irradiation to reach the InGaN layer (emissive layer) 12 increases, and as a result, the time it takes for the crystallinity of the GaN layer (cap layer) 13 to improve increases.

[0049] (Thickness of the cap layer) Figure 13 is a graph showing the ratio (luminescence intensity ratio) of the luminescence intensity when an SiO2 film 14 is formed on the GaN layer (cap layer) 13 to the luminescence intensity when the SiO2 film 14 is not formed, for samples with varying thicknesses of the GaN layer (cap layer) 13, as shown in Figure 1.

[0050] As shown in Figure 13, it can be seen that the luminescence intensity ratio improves as the thickness of the GaN layer (cap layer) 13 increases. The thickness of the GaN layer (cap layer) 13 is preferably 5 nm or more. If the thickness of the GaN layer (cap layer) 13 is less than 5 nm, the InGaN layer (emissive layer) 12 will be damaged by sputtering during the formation of the SiO2 film 14, resulting in a lack of improvement in luminescence efficiency, which is undesirable.

[0051] Furthermore, the thickness of the GaN layer (cap layer) 13 is preferably 150 nm or less. If the thickness of the GaN layer (cap layer) 13 exceeds 150 nm, the distance between the InGaN layer (emissive layer) 12 and the SiO2 film 14 becomes too large, and Si does not diffuse close to the InGaN layer (emissive layer) 12, so the effect of improving luminous efficiency cannot be obtained, which is undesirable. Moreover, the thickness of the GaN layer (cap layer) 13 is more preferably 100 nm or less. Since the distance that a laser with a wavelength of 325 nm can penetrate into the GaN layer (cap layer) 13 is approximately 100 nm, if the thickness of the GaN layer (cap layer) 13 exceeds 100 nm, the temperature rise due to the heat generated by the GaN layer (cap layer) 13 cannot be sufficiently obtained, so the effective effect of improving luminous efficiency cannot be obtained, which is undesirable.

[0052] (Thickness of the oxide film) In the present invention, the thickness of the oxide film (SiO2 film, ZnO film) 14 formed on the GaN layer (cap layer) 13 is preferably 1 nm or more, because if it is less than 1 nm, it is difficult to form a thin film.

[0053] (How to manufacture hibiscus) The present invention provides a method for manufacturing a light-emitting element, comprising the steps of forming a light-emitting layer 12 having a quantum well structure on a substrate 10, forming a cap layer 13 made of GaN on the light-emitting layer 12, and forming an oxide film 14 on the cap layer 13, wherein the oxide film 14 is made of an oxide of an element that can diffusely penetrate into the Ga vacancies present in the GaN-composed cap layer 13.

[0054] The oxide film 14 is preferably made of an SiO2 film or a ZnO film and formed by sputtering.

[0055] Furthermore, it is preferable to further include a step of irradiating the surface of the oxide film 14 formed on the cap layer 13 with light having a wavelength with energy greater than the bond energy between the elements constituting the oxide film 14 (Si in the case of an SiO2 film, and Zn in the case of a ZnO film) and oxygen.

[0056] The method may further include a step of removing the oxide film 14 formed on the cap layer 13.

[0057] Furthermore, at least one or both of the elements that constitute the oxide film 14, or oxygen, are present within the cap layer 13.

[0058] According to the method for manufacturing a light-emitting element in the present invention, a light-emitting element with improved luminous efficiency can be obtained in a light-emitting element composed of a GaN-based semiconductor. In particular, a light-emitting element with high luminous efficiency can be realized in the green (510 nm) and yellow-green (540 nm) wavelength regions.

[0059] (structure of a light-emitting element) Figure 14 is a schematic cross-sectional view showing the configuration of a light-emitting element (light-emitting diode) manufactured by the light-emitting element manufacturing method of the present invention.

[0060] As shown in Figure 14, the light-emitting element 1 comprises an n-type GaN layer 11 formed on a substrate 10, a light-emitting layer 12 having a quantum well structure formed on the n-type GaN layer 11, a cap layer 13 made of p-type GaN formed on the light-emitting layer 12, and a ZnO film 14 formed on the cap layer 13.

[0061] Here, it is preferable that the ZnO film 14 is a film formed by sputtering. Furthermore, it is preferable that the surface of the ZnO film 14 is irradiated with light of a wavelength having energy greater than the bond energy between zinc (Zn) and oxygen (O).

[0062] Since the ZnO film 14 is conductive, by forming a transparent electrode film 15 on the ZnO film 14, and then forming electrodes 20 and 21 on the transparent electrode film 15 and on the n-type GaN layer 11, it is possible to inject current into the light-emitting layer 12 and extract light from the light-emitting layer 12.

[0063] On the other hand, when an SiO2 film is formed on the cap layer 13, since the SiO2 film is an insulating film, as shown in Figure 15, after removing the SiO2 film formed on the cap layer 13, a transparent electrode film 15 is formed on the cap layer 13, and electrodes 20 and 21 are formed on the transparent electrode film 15 and on the n-type GaN layer 11, so that current can be injected into the light-emitting layer 12 and light can be extracted from the light-emitting layer 12. Furthermore, even if the SiO2 film formed on the cap layer 13 is removed, the effect of improving luminous efficiency is maintained, so a light-emitting element with high luminous efficiency can be obtained.

[0064] (A variation of a light-emitting element) Figure 16 is a cross-sectional view showing a modified example of the light-emitting element in the present invention.

[0065] The light-emitting element 1 shown in Figure 16 is an improved version of the light-emitting element 1 shown in Figure 14, in which a plasmon layer 30 is further formed on the ZnO film 14, which resonates with the light emitted from the light-emitting layer 12. Here, the plasmon layer 30 is composed of a thin metal film or metal nanoparticles made of materials such as Ag, Al, Au, or Cu.

[0066] It is known that the luminescence efficiency can be improved by the plasmon effect by forming a plasmon layer 30 on the surface of a p-type GaN layer 13 formed on an InGaN light-emitting layer 12 (Non-Patent Literature 1). However, there is a problem that metal atoms diffuse into the p-type GaN layer 13 from the metal thin film or metal nanoparticles constituting the plasmon layer 30, causing the structure of the plasmon layer 30 to break down over time and reducing the plasmon effect.

[0067] In this modified example, as shown in Figure 16, the light-emitting element 1 has a plasmon layer 30 formed on a p-type GaN layer (cap layer) 13 via a ZnO film 14. This prevents metal atoms from diffusing into the p-type GaN layer 13 from the metal thin film or the like that constituting the plasmon layer 30. As a result, the structure of the plasmon layer 30 is stabilized, and the plasmon effect can be maintained.

[0068] In this modified example, the light-emitting element 1 exhibits improved luminous efficiency by forming a ZnO film 14 on the p-type GaN layer 13, and further improved luminous efficiency is achieved by forming a plasmon layer 30 on the ZnO film 14, thereby realizing a light-emitting element 1 with even higher luminous efficiency.

[0069] In this modified example, if the thickness of the ZnO film 14 is too large, the electric field of the plasmon layer 30 will not reach the InGaN light-emitting layer 12, and the plasmon effect will not be exhibited. Therefore, the thickness of the ZnO film 14 is preferably 10 nm or less.

[0070] Although the present invention has been described above with reference to preferred embodiments, this description is not limiting, and various modifications are, of course, possible. For example, in the above embodiments, an oxide film 14 made of an SiO2 film or a ZnO film was formed on the p-type GaN layer (cap layer) 13, but a nitride film such as a Si3N4 film may also be formed. In this case, for example, by irradiating the surface of the Si3N4 film with a laser having a wavelength with energy greater than the bond energy between Si and N (nitrogen), the bond between Si and N is broken, and Si diffuses into the Ga vacancies in the p-type GaN layer (cap layer) 13, thereby improving the crystallinity of the p-type GaN layer (cap layer) 13.

[0071] Furthermore, although an InGaN layer having a single quantum well structure was exemplified as the light-emitting layer 12 in the above embodiment, the invention is not limited to this, and an InGaN layer having a multiple quantum well structure may also be used. In addition, the light-emitting layer 12 is not limited to an InGaN layer, and an AlGaN layer or the like may also be used.

[0072] Furthermore, although a light-emitting diode was used as an example of the light-emitting element 1 in the above embodiment, the invention is not limited to this and can also be applied to semiconductor lasers, for example. [Explanation of Symbols]

[0073] 1 Light-emitting element 10 circuit boards 11 (n-type) GaN layer 12. InGaN layer (light-emitting layer) 13 (p-type) GaN layer (cap layer) 14 Oxide film (SiO2 film, ZnO film) 15 Transparent electrode film 20, 21 electrodes 30 Plasmon layer

Claims

1. A method for manufacturing a light-emitting element composed of a GaN-based semiconductor, A step of forming a light-emitting layer having a quantum well structure on a substrate, The process of forming a cap layer made of GaN on the light-emitting layer, On the aforementioned cap layer, SiO ２ A step of forming a film or a ZnO film, The SiO formed on the cap layer ２ On the surface of the film or ZnO film, the SiO ２ A step of irradiating the film or ZnO film with light having a wavelength having an energy greater than the bonding energy between silicon or zinc and oxygen, The SiO ２ A step of forming a plasmon layer on the surface of a film or ZnO film that resonates with light emitted from the light-emitting layer and causes plasmon resonance. Equipped with, In the process of irradiating with light, the SiO ２ A method for manufacturing an light-emitting element, wherein the silicon or zinc constituting the film or ZnO film breaks its bond with the oxygen upon irradiation with the light and diffuses into the Ga vacancies present in the cap layer.

2. The method for manufacturing a light-emitting element according to claim 1, wherein the plasmon layer is composed of a thin metal film or metal nanoparticles.

3. A method for manufacturing a light-emitting element composed of a GaN-based semiconductor, A step of forming a light-emitting layer having a quantum well structure on a substrate, The process of forming a cap layer made of GaN on the light-emitting layer, The steps include forming a ZnO film on the cap layer, A step of irradiating the surface of the ZnO film formed on the cap layer with light having a wavelength with energy greater than the bonding energy between zinc (Zn) and oxygen (O), The process of forming a transparent electrode on the ZnO film, Equipped with, A method for manufacturing an light-emitting element, wherein, in the step of irradiating with light, the zinc (Zn) constituting the ZnO film has its bond with oxygen (O) broken by the irradiation of light and diffuses into the Ga vacancies present in the cap layer.

Images