Method for manufacturing gallium nitride light-emitting element and lighting device

Abstract

Provided is a method for manufacturing a GaN light-emitting element capable of adjusting directional characteristics. The method includes: forming an epitaxial structure by epitaxially growing an n-type GaN layer (12), an MQW layer (14), and a p-type GaN layer (16) in this order on a sapphire substrate (10); forming a p-type electrode, a metal reflective film, a metal substrate, and a support substrate on the p-type GaN layer (16); overturning the epitaxial structure up and down; peeling off the sapphire substrate (10) to expose the n-type GaN layer (12) on the surface; etching the n-type GaN layer (12) exposed on the surface to adjust the length of a resonator formed between the surface of the metal reflective film and the surface of the n-type GaN layer (12); and forming an n-electrode (24).

Description

Technical Field

[0001] This invention relates to a method for manufacturing a gallium nitride light-emitting element and an illumination device. Background Technology

[0002] The following research is underway: to limit the pointing angle by incorporating lenses in LED devices to focus light while reducing the pointing angle of light emitted from gallium nitride (GaN) light-emitting element (LED) chips.

[0003] However, in the case of lenses, even slight changes in directionality require modifications to the mold, leading to increased costs. Furthermore, in ultraviolet and deep ultraviolet light, quartz lenses are used to account for absorption, which also makes the lenses more expensive.

[0004] Therefore, as a method to reduce the directivity of LED devices by focusing light without using lenses, research is being conducted on forming photonic crystals by creating apertures on the surface of LED chips with a spacing of hundreds of nanometers.

[0005] Patent Document 1 discloses an invention related to gallium nitride-based photonic crystals and their manufacturing methods. Specifically, it describes an invention aimed at obtaining a nitride semiconductor with reduced dislocation density and good crystallinity over a wide region during epitaxial growth to provide high-performance gallium nitride-based semiconductor devices, gallium nitride-based semiconductor substrates, and gallium nitride-based photonic crystals with high yield. The invention comprises the following steps: forming a gallium nitride-based semiconductor layer on a substrate; arranging and forming a plurality of trenches in the gallium nitride-based semiconductor layer; and performing heat treatment in a nitrogen-containing atmosphere to deform at least two adjacent trenches among the plurality of trenches, forming continuous voids inside the gallium nitride-based semiconductor layer corresponding to the positions of the deformed trenches, and forming a gallium nitride-based semiconductor device on the gallium nitride-based semiconductor layer having the voids.

[0006] In addition, Patent Document 2 describes a photonic crystal light-emitting diode with the goal of providing a photonic crystal light-emitting diode that is resistant to degradation over a long period of time and has high energy efficiency and luminous efficiency. The photonic crystal light-emitting diode is described as follows: In a light-emitting diode having a structure in which a first semiconductor layer, an active layer, and a second semiconductor layer are stacked in this order, and a first electrode is electrically connected to the first semiconductor layer and a second electrode is electrically connected to the second semiconductor layer, the apertures penetrating at least the first semiconductor layer and the active layer are arranged in a two-dimensional periodic manner to form a photonic crystal structure, and the first electrode covers the area of ​​the first semiconductor layer except for the apertures and the first non-current injection region surrounding the apertures.

[0007] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2004-111766 Patent document 2: Japanese Patent Application Publication No. 2011-54828. Summary of the Invention

[0008] The problem the invention aims to solve However, in the case of light-emitting elements such as LEDs made of gallium nitride (GaN), the technology for adjusting their pointing characteristics has not yet been established.

[0009] The purpose of this invention is to provide a method for manufacturing a GaN light-emitting element with adjustable pointing characteristics.

[0010] Solution for solving the problem The present invention discloses a method for manufacturing a gallium nitride light-emitting element, comprising the following steps: sequentially stacking a metal reflective film, a p-type gallium nitride layer, a multiple quantum well layer, and an n-type gallium nitride layer on a substrate; and adjusting the directional characteristics of the emitted light by adjusting the length of a resonator formed between the surface of the metal reflective film and the surface of the n-type gallium nitride layer.

[0011] In one embodiment of the present invention, in the step of adjusting the resonator length, when the film thickness between the surface of the metal reflective film and the surface of the n-type gallium nitride layer is set to d, the refractive index is set to n, the wavelength of the emitted light is set to λ, and the integer is set to m, the film thickness d is adjusted to... .

[0012] In another embodiment of the invention, the directionality of the emitted light is reduced by setting the value of m to a small value.

[0013] In addition, the present invention provides a method for manufacturing a gallium nitride (GaN) light-emitting element, comprising the following steps: epitaxially growing an n-type GaN layer, a multiple quantum well layer, and a p-type GaN layer sequentially on a sapphire substrate to form an epitaxial structure; forming a p-type electrode on the p-type GaN layer; forming a metal reflective film, a metal substrate, and a support substrate on the p-type electrode; flipping the epitaxial structure so that the support substrate is below and the sapphire substrate is above; peeling off the sapphire substrate, which is located at the top through the flipping step, to expose the n-type GaN layer on the surface; etching the n-type GaN layer to adjust the resonator length formed between the surface of the metal reflective film and the surface of the n-type GaN layer; forming an n-type electrode on the n-type GaN layer; and peeling off the support substrate.

[0014] In one embodiment of the present invention, in the step of etching the n-type gallium nitride layer, when the film thickness between the surface of the metal reflective film and the surface of the n-type gallium nitride layer is set to d, the refractive index is set to n, the wavelength of the emitted light is set to λ, and the integer is set to m, it becomes... Etching is performed in this manner.

[0015] In another embodiment of the present invention, the emission wavelength of the gallium nitride light-emitting element is 380nm~390nm.

[0016] In addition, the present invention is a lighting device comprising: a gallium nitride light-emitting element manufactured by the above method; and an illumination optical system that illuminates an object with light from the gallium nitride light-emitting element.

[0017] The effects of the invention According to the present invention, the pointing characteristics of a GaN light-emitting element can be adjusted. In particular, the pointing characteristics of the emitted light can be adjusted by adjusting the film thickness during the manufacturing process of the GaN light-emitting element. Attached Figure Description

[0018] FIG. 1A This is a schematic cross-sectional view (one of the embodiments) illustrating the manufacturing method.

[0019] FIG. 1B This is a schematic cross-sectional view (second one) illustrating the manufacturing method of the embodiment.

[0020] FIG. 1C This is a schematic cross-sectional view (third one) illustrating the manufacturing method of the embodiment.

[0021] FIG. 1D This is a schematic cross-sectional view (fourth) illustrating the manufacturing method of the embodiment.

[0022] FIG. 1E This is a schematic cross-sectional view (fifth) illustrating the manufacturing method of the embodiment.

[0023] FIG. 1F This is a schematic cross-sectional view (sixth) illustrating the manufacturing method of the embodiment.

[0024] FIG. 1G This is a schematic cross-sectional view (seventh) illustrating the manufacturing method of the embodiment.

[0025] FIG. 1H This is a schematic cross-sectional view (eighth) illustrating the manufacturing method of the embodiment.

[0026] FIG. 1I This is a schematic cross-sectional view (nine) illustrating the manufacturing method of the embodiment.

[0027] FIG. 2 This is a schematic cross-sectional view of a GaN light-emitting element according to an embodiment.

[0028] FIG. 3This is a diagram showing the structure of the lighting device and the exposure device according to the embodiment.

[0029] FIG. 4 This is a diagram showing the structure of the light source unit.

[0030] FIG. 5 This is a top view showing the position of the V-chip sample in the embodiment.

[0031] FIG. 6 This is a graph showing the results of the integrating sphere measurement in an embodiment.

[0032] FIG. 7 This is the emission spectrum of an embodiment.

[0033] FIG. 8 This is an IL characteristic diagram of an embodiment.

[0034] FIG. 9 This is the IV characteristic diagram of the embodiment.

[0035] FIG. 10 This is a graph showing the results of the directional characteristic measurement for a reference in the embodiment.

[0036] FIG. 11 This is a graph showing the measurement results of the directional characteristics of the GaN light-emitting element after film thickness adjustment in the embodiment. Detailed Implementation

[0037] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0038] The basic principle of this embodiment is that, considering that the directional characteristics of light emitted from the GaN light-emitting element can be changed by adjusting the resonator length of the resonator structure included in the GaN stacked structure constituting the GaN light-emitting element, the GaN light-emitting element is manufactured by adjusting the resonator length and its directional characteristics are controlled to the desired characteristics.

[0039] The inventors of this application discovered that in a GaN layer stack structure sequentially grown on a substrate, the directional characteristics of light emitted from a GaN light-emitting element can be altered by adjusting the length of the resonator formed between the surface of the GaN layer and the surface of the underlying metal reflective film, specifically by adjusting the film thickness of the n-type GaN layer and the p-type GaN layer constituting the resonator length. When the emission wavelength is set to λ, the refractive index is set to n, and m is set to an integer (m=1, 2, 3, ...), the directional characteristics of light emitted from the GaN light-emitting element can be changed. Resonator length = m·λ / n Given the resonator length, it was found that the directivity could be controlled by adjusting the resonator length.

[0040] Furthermore, the inventors of this application have discovered that the thinner the film thickness of the resonator, the narrower the directivity. This means that in the above formula, the smaller m is set, the greater the effect of reducing the directivity of light.

[0041] FIGS. 1A-1I This is a cross-sectional view schematically illustrating a method for manufacturing the GaN light-emitting element (LED) in this embodiment.

[0042] like FIG. 1A As shown, a low-temperature buffer layer (not shown) and an undoped GaN (u-GaN) layer (not shown) are stacked on a sapphire substrate 10 using a metal-organic vapor deposition (MOCVD) apparatus, and an n-GaN layer (n-type GaN layer) 12, a multiple quantum well (MQW) layer 14 and a p-GaN layer (p-type GaN layer) 16 are sequentially stacked on it to grow an epitaxial structure that emits light at 385 nm (380 nm~390 nm).

[0043] More specifically, the n-GaN layer 12 is composed of an n-GaN contact layer, a (AlInGaN) / (InGaN;Si)n-SLS (superlattice structure) layer, and a (AlGaN;Si) layer. Here, for example, (GaN;Si) represents GaN doped with Si.

[0044] In addition, the multiple quantum well (MQW) layer 14 is composed of a total of six MQW layers (InGaN / AlGaN).

[0045] In addition, more specifically, the p-GaN layer 16 is composed of a p-GaN (GaN; Mg) contact layer and a (AlGaN; Mg / GaN; Mg) p-SLS (superlattice structure) layer.

[0046] In this embodiment, "GaN layer" does not necessarily refer to a single layer composed of GaN, but rather to a single layer or multiple layers composed of GaN, such as AlInGaN, InGaN, and AlGaN. In short, it refers to a single layer or multiple layers with GaN as the main component.

[0047] Furthermore, the emission wavelength of the epitaxial layer in this embodiment is 385 nm. However, when the wavelength is set to be greater than 385 nm, the basic epitaxial structure is the same. However, due to the band gap energy, compared with the wavelength greater than 385 nm, the Al content of the (InGaN / AlInGaN)MQW emission layer 14 is increased and the In content is decreased at a wavelength of 385 nm.

[0048] Next, as FIG. 1B As shown, a p-electrode (p-type electrode: ITO, etc.) and a metal reflective film (Ag, etc.) are deposited on an epitaxial structure layer emitting light at 385 nm. FIG. 1BIn the text, the p-electrode and the metal reflective film are represented together as p-electrode and reflective film 18.

[0049] Next, as FIG. 1C As shown, a metal substrate (CuW, CuMo, etc.) 20 is bonded to the p-electrode and the metal reflective film 18.

[0050] Next, as FIG. 1D As shown, a support substrate (sapphire, Si substrate, etc.) 22 is bonded to a metal substrate 20. FIG. 1D The stacked structure shown, from bottom to top, consists of a sapphire substrate 10, an n-GaN layer 12, an MQW layer 14, a p-GaN layer 16, a p-electrode and reflective film 18, a metal substrate 20, and a support substrate 22.

[0051] Next, as FIG. 1E As shown, FIG. 1D The epitaxial structure is flipped 180° vertically, with the sapphire substrate 10 at the top. The sapphire substrate 10 is then lifted off using a laser, exposing the n-GaN layer 12 to the surface. That is, the n-GaN layer 12 is exposed. FIG. 1D The stacked structure after the epitaxial structure is flipped 180° from bottom to top is as follows: support substrate 22 / metal substrate 20 / p-electrode and reflective film 18 / p-GaN layer 16 / MQW layer 14 / n-GaN layer 12 / sapphire substrate 10. The n-GaN layer 12 is exposed on the top surface by lifting off the topmost sapphire substrate 10 (and buffer layer).

[0052] Next, as FIG. 1F As shown, the n-GaN layer 12 on the surface is etched to adjust the film thickness. The adjustment is made by etching the n-GaN layer 12 so that the total film thickness from the n-GaN layer 12 to the p-GaN layer 16 is a specified film thickness.

[0053] Next, as FIG. 1G As shown, trenches are formed from the surface of the n-GaN layer 12 up to the metal substrate 20 to separate the epitaxial structure.

[0054] Next, as FIG. 1H As shown, n-electrodes (n-type electrodes) 24 are formed on the n-GaN layers 12 in the separated regions.

[0055] Finally, as FIG. 1I As shown, the support substrate 22 is peeled off and cut to manufacture LED chips (V-chip structure LED chip: a vertical LED chip with electrodes arranged in a vertical structure).

[0056] FIG. 2A schematic cross-sectional view of a GaN light-emitting element with a V-chip structure fabricated as described above, and an example of its film thickness, are shown. In the figure, a: The film thickness, including the thickness from the surface of the n-GaN layer 12 to the bottommost quantum well layer 14a in the quantum well layer and quantum barrier layer constituting the MQW layer 14, is 1149.23 nm. b: The film thickness, including the surface of the bottommost quantum barrier layer (the interface between the quantum barrier layer and the quantum well layer 14a) from the quantum well layer and quantum barrier layer constituting the MQW layer 14 to the thickness of the p-GaN layer 16, is 152.56 nm. c: The sum of a and b = 1301.79nm.

[0057] Next, refer to FIG. 3 and FIG. 4 This invention describes an illumination device that includes a GaN light-emitting element manufactured by the manufacturing method described in the above embodiments, and an exposure device that includes the illumination device.

[0058] FIG. 3 This is a schematic diagram showing the structure of an exposure apparatus having an illumination device IU that uses a GaN light-emitting element manufactured by the manufacturing method described in the above embodiments as a light source. FIG. 4 (A) is a top view schematically showing the structure of the light source unit 120 that supplies exposure light to the lighting device IU. FIG. 4 (B) is a diagram that schematically shows the internal structure of the light source unit 120 and the output optical system 130.

[0059] exist FIG. 3 In the illumination device IU, there are: a first focusing optical system 140 that focuses the exposure light from the light source unit 120 that has passed through the output optical system 130; a compound eye lens FEL into which the exposure light from the first focusing optical system 140 is incident; and a second focusing optical system 160 that focuses the exposure light from the compound eye lens FEL to illuminate the mask REI, which is the surface to be illuminated.

[0060] In addition, the exposure apparatus includes an illumination device IU and a projection optical system PO, the projection optical system PO forming a pattern image on a mask illuminated by the illumination device IU on the wafer, which is the substrate to be exposed.

[0061] Next, refer to FIG. 4 Explain the light source unit 120 and the output optical system 130.

[0062] exist FIG. 4 In (A), the light source unit 120 includes, for example, a plurality of (in) arranged on the substrate 121. FIG. 3(A) shows 5×5 LED (Light Emitting Diode) chips 123. These LED chips are GaN light-emitting elements manufactured by the manufacturing method of the above embodiment. Furthermore, the number of LED chips 123 can be appropriately varied as needed. Each of the plurality of LED chips 123 has a light-emitting portion 231, and the peak wavelength of the light emitted from the light-emitting portion 231 is in the range of 380nm to 390nm. That is, the light-emitting portion 231 is an ultraviolet LED (UV LED). The peak wavelength of the light emitted from the light-emitting portion 231 is more preferably 385nm. The light-emitting surface of the light-emitting portion 231 can be square, or it can be a rectangle, hexagon, or other polygon. Furthermore, the LED chips 123 can also be arranged on, for example, a heat sink instead of a substrate.

[0063] Reference FIG. 4 (B) illustrates the structure of the light source unit 120 and the output optical system 130. FIG. 3 In (B), the two directions in which the LED chips 123 are arranged are designated as the X and Y directions. The X and Y directions are orthogonal. Furthermore, the direction orthogonal to the X and Y directions is designated as the Z direction. The Z direction is approximately aligned with the direction of light propagation emitted from the light-emitting unit 231. Additionally, in FIG. 4 In (B), only four LED chips 123 arranged in a row along the Y direction are shown for clarity.

[0064] like FIG. 4 As shown in (B), the output optical system 130 includes multiple magnifying optical systems for forming magnified images of the light-emitting portions 231 of each LED chip 123. Each magnifying optical system is arranged in a manner corresponding to the arrangement of the LED chips 123, and is a two-sided telecentric optical system that magnifies and projects the light-emitting portions 231 based on magnification. Furthermore, in FIG. 4 In (B), the magnifying optical system of the output optical system 130 is illustrated using two positive lenses, but the number of lenses constituting the magnifying optical system is not limited to two. Furthermore, the magnifying optical system can also be composed of a reflection system or a reflection-refraction system. Moreover, the output optical system 130 can replace the magnifying optical system or, in addition to the magnifying optical system, possess an equal-magnification optical system or a reduction optical system.

[0065] exist FIG. 3 and FIG. 4 In the illustrated embodiment, each magnifying optical system of the output optical system 130 forms a magnified image of the light-emitting portion 231 near the final optical component of the output optical system 130. Thus, multiple densely arranged light source images are located near the final optical component of the output optical system 130.

[0066] return FIG. 3Explain the components of the lighting device IU.

[0067] The first focusing optical system 140 is configured such that the front focal point is located at or near the position of the light source image formed by the light source unit 120 and the output optical system 130, and provides Köhler illumination to the incident surface of the compound eye lens FEL.

[0068] A compound eye lens (FEL) is constructed by arranging, for example, multiple lens elements with positive refractive power in a longitudinal and dense manner, such that their optical axes are parallel to a reference optical axis AX. Each lens element constituting the compound eye lens (FEL) has a rectangular cross-section similar to the shape of the illumination field to be formed on the photomask REI (and consequently the shape of the exposure area to be formed on the wafer W).

[0069] Therefore, the light beam incident on the compound eye lens FEL is wavefront-splitting by multiple lens elements, forming a light source image at or near the back focal plane (emission surface) of each lens element. That is, a substantial surface light source, i.e., a secondary light source, is formed at or near the back focal plane (emission surface) of the compound eye lens FEL, consisting of multiple light source images.

[0070] Here, when focusing on one lens element of the compound eye lens FEL, the images of multiple light source images formed by the light source unit 120 and the output optical system 130 are formed on or near the back focal plane (emission plane) of the lens element, and these multiple light source images are distributed in a region with a shape similar to the region where the multiple LED chips 123 are arranged. Therefore, the region where the multiple LED chips 123 are arranged and the cross-sections of each lens element of the compound eye lens FEL can be similar in shape to each other.

[0071] Furthermore, a light beam from a secondary light source formed on or near the back focal plane (emission surface) of the compound eye lens FEL is incident on an aperture stop 150 disposed nearby. In addition, in this embodiment, the back focal plane (emission surface) of the compound eye lens FEL and the LED chip arrangement surface of the light source unit 120 are optically conjugate.

[0072] The aperture stop 150 is positioned approximately optically conjugate to the entrance pupil plane of the projection optical system PO, and has a variable aperture section for defining a range that facilitates illumination by the secondary light source. Exposure light from the secondary light source, passing through the aperture stop 150, is focused by the second focusing optical system 160 and superimposedly illuminates the mask REI, which forms a predetermined pattern.

[0073] Then, exposure light from the mask REI illuminated by the illumination device IU (exposure light passing through the pattern within the illumination field on the mask REI) is incident on the projection optical system PO, forming a pattern image of the mask REI on the wafer W, which serves as the substrate to be exposed. Thus, the pattern of the mask REI is exposed in the exposure area of ​​the wafer W. Furthermore, the projection magnification of the projection optical system PO can be a reduction magnification, a magnification magnification, or an equal magnification. Additionally, the projection optical system PO can be a refractive optical system, a reflective optical system, or a reflective-refractive optical system. Example

[0074] According to the manufacturing method described above, GaN light-emitting elements were fabricated on a wafer.

[0075] Furthermore, after the epitaxial structure is grown, the film thickness of the final quantum barrier layer in the p-GaN layer 16 and MQW layer 14 is measured by cross-sectional TEM observation, and the growth rate is calculated based on the film thickness measurement results.

[0076] Subsequently, the growth time of the p-GaN layer 16 is adjusted based on the calculated growth rate, thereby adjusting the film thickness from the last barrier layer in the MQW layer 14 to the p-GaN layer 12 to the specified film thickness.

[0077] The film thicknesses of each layer are as follows.

[0078] n-GaN layer 12: 1098.77nm MQW layer 14 (6 pairs of quantum well layers and quantum barrier layers): 50.46nm The final quantum barrier layer: 30.21nm p-GaN layer 14: 122.35nm Additionally, as a comparative example (reference), a GaN light-emitting element with unadjusted film thickness was fabricated on a wafer. In the reference, both the n-GaN layer 12 and the p-GaN layer 14 were set to have a thicker film thickness compared to the GaN light-emitting element of the embodiment.

[0079] FIG. 5 A top view of an embodiment of the GaN wafer is shown. FIG. 5 In the process, at five positions marked with circled numbers 1 to 5, a reference (without adjusted film thickness) and a V chip with adjusted film thickness are taken out and mounted on an Al substrate. The electrical characteristics, optical output, and wavelength are then measured using an integrating sphere.

[0080] Furthermore, observations of the appearance of the reference (unadjusted film thickness) and the V-chip with adjusted film thickness revealed no difference in their surface conditions.

[0081] FIG. 6The results of measuring the electrical characteristics of a reference (unadjusted film thickness) and a V-chip with adjusted film thickness using an integrating sphere are shown. FIG. 6 (a) shows the current, voltage, total radiated flux, peak wavelength, and FWHM (full width at half maximum) of the V-chip as a reference (unadjusted film thickness) and an adjusted film thickness at IF (forward current) = 350 mA. Additionally, FIG. 6 (b) shows the current, voltage, total radiative flux, peak wavelength, and FWHM of the V chip as a reference (unadjusted film thickness) and with adjusted film thickness at IF (forward current) = 500mA. No significant differences in electrical characteristics were observed between the two.

[0082] FIG. 7 The emission spectra of a reference (unadjusted film thickness) and a V-chip with adjusted thickness are shown. The horizontal axis represents wavelength, and the vertical axis represents relative output power. FIG. 7 (a) is the emission spectrum of the V chip as a reference (without adjusted film thickness). FIG. 7 (b) shows the emission spectrum of the V chip with the film thickness adjusted. No significant differences were observed in the emission spectra of the two.

[0083] FIG. 8 The IL characteristics of a reference (unadjusted film thickness) and a V-chip with adjusted film thickness are shown. The horizontal axis represents IF (forward current), and the vertical axis represents relative luminance. FIG. 8 (a) is the IL characteristic of the reference (unadjusted film thickness) V chip. FIG. 8 (b) shows the IL characteristics of the V chip with adjusted film thickness. No significant difference was observed in the IL characteristics between the two.

[0084] FIG. 9 The diagram shows the IV characteristics of a reference (unadjusted film thickness) and a V-chip with adjusted film thickness. The horizontal axis represents VF (forward voltage), and the vertical axis represents IF (forward current). FIG. 9 (a) is the IV characteristics of the reference (unadjusted film thickness) V chip. FIG. 9 (b) shows the IV characteristics of the V chip with adjusted film thickness. No significant difference was observed in the IV characteristics between the two.

[0085] FIG. 10 and FIG. 11 The results of the pointing characteristics measurements for a reference (unadjusted film thickness) and a V-chip with adjusted film thickness are shown. In both graphs, the horizontal axis represents relative radiation intensity, and the vertical axis represents relative angle. FIG. 10 It is a reference to the pointing characteristics of the V chip, and all five positions with circled numbers 1 to 5 show the same pointing characteristics.

[0086] on the other hand,FIG. 11 The pointing characteristics of the V-chip with adjusted film thickness are shown to change at five positions marked with circled numbers 1 to 5. When compared with the same position on the wafer with the adjusted film thickness, it is confirmed that the pointing of the chip with the adjusted film thickness becomes narrower.

[0087] Furthermore, in the V-chip with adjusted film thickness, the pointing characteristics change depending on the position on the wafer. This is believed to be because the film thickness, i.e., the resonator length, deviates according to the position on the wafer, and the pointing characteristics change due to this deviation. This means that the pointing characteristics of the V-chip can be precisely controlled by suppressing the deviation in film thickness and precisely controlling the resonator length.

[0088] Furthermore, in the V-chip with adjusted film thickness, it was confirmed that the output within ±30 degrees directly above the overall output was approximately 7% higher than the reference at the position marked with the circled number 5.

[0089] As explained above, according to this embodiment, by adjusting the resonator structure included in the GaN stacked structure constituting the GaN light-emitting element, specifically the resonator length formed between the surface of the GaN layer and the surface of the underlying metal reflective film, the directional characteristics of the light emitted from the GaN light-emitting element can be controlled to the desired characteristics. This reduces the directionality of the light emitted from the GaN light-emitting element, thereby improving the output within a certain angular range directly above the overall output.

[0090] Explanation of symbols 10: Sapphire substrate, 12: n-GaN layer, 14: MQW layer, 16: p-GaN layer, 18: p-electrode and metal reflective film, 20: metal substrate, 22: support substrate, 24: n-electrode.

Claims

1. A method of manufacturing a gallium nitride light emitting element, comprising the steps of: sequentially stacking a metal reflective film, a p-type gallium nitride layer, a multiple quantum well layer, and an n-type gallium nitride layer on a substrate; and adjusting a directivity characteristic of emitted light by adjusting a resonator length formed between a surface of the metal reflective film and a surface of the n-type gallium nitride layer.

2. The method of manufacturing a gallium nitride light emitting element according to claim 1, wherein, in the step of adjusting the resonator length, when a film thickness between the surface of the metal reflective film and the surface of the n-type gallium nitride layer is set as d, a refractive index is set as n, a wavelength of the emitted light is set as λ, and an integer is set as m, the film thickness d is adjusted to d = mλ / 2n.

3. The method of manufacturing a gallium nitride light emitting element according to claim 2, wherein the directivity of the emitted light is narrowed by setting the value of m to be small.

4. A method of manufacturing a gallium nitride light emitting element, comprising the steps of: forming an epitaxial structure by epitaxially growing an n-type gallium nitride layer, a multiple quantum well layer, and a p-type gallium nitride layer on a sapphire substrate in this order; forming a p-type electrode on the p-type gallium nitride layer; forming a metal reflective film, a metal substrate, and a support substrate on the p-type electrode; turning upside down the epitaxial structure with the support substrate on the bottom and the sapphire substrate on the top; peeling off the sapphire substrate located on the top by the step of turning upside down to expose the n-type gallium nitride layer on the surface; etching the n-type gallium nitride layer to adjust a resonator length formed between a surface of the metal reflective film and a surface of the n-type gallium nitride layer; forming an n-type electrode on the n-type gallium nitride layer; and peeling off the support substrate.

5. The method of manufacturing a gallium nitride light emitting element according to claim 4, wherein, in the step of etching the n-type gallium nitride layer, when a film thickness between the surface of the metal reflective film and the surface of the n-type gallium nitride layer is set as d, a refractive index is set as n, a wavelength of the emitted light is set as λ, and an integer is set as m, the etching is performed in such a manner that d = mλ / 2n.

6. The method of manufacturing a gallium nitride light emitting element according to any one of claims 1 to 5, wherein a light emitting wavelength of the gallium nitride light emitting element is 380 nm to 390 nm.

7. An illuminating device, comprising: a gallium nitride light emitting element manufactured by the method of manufacturing according to any one of claims 1 to 5; and an irradiation optical system that irradiates light from the gallium nitride light emitting element toward an object. 。 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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