Gallium nitride-based laser with high thermal stability and preparation method thereof

Abstract

The invention provides a gallium nitride-based laser with high thermal stability and a preparation method thereof, and relates to the field of lasers, and the gallium nitride-based laser comprises an n-surface electrode, an n-type substrate layer, an n-type limiting layer, an n-type waveguide layer, a quantum well active region, a p-type waveguide layer, a p-type electron blocking layer, a p-type limiting layer, a p-type contact layer and a p-surface electrode which are sequentially arranged from top to bottom; an epitaxial growth method is adopted, the growth temperature of the quantum well active region is controlled to be 680 DEG C, and the growth temperatures of the p-type electron blocking layer, the p-type limiting layer and the p-type contact layer are all controlled to be 980 DEG C. The gallium nitride-based laser is good in thermal stability and excellent in photoelectric property.

Description

Technical Field

[0001] This invention relates to the field of lasers, and more specifically, to a gallium nitride-based laser with high thermal stability and its fabrication method. Background Technology

[0002] Semiconductor lasers have been widely used due to their small size, long lifespan, and low cost. Among them, gallium nitride (GaN)-based semiconductor lasers, especially blue-green lasers, are widely used in industrial manufacturing, laser displays, underwater communications, and biomedicine. However, the development of green lasers still faces several technical challenges, particularly in epitaxial growth. High-In-content InGaN materials are often used as quantum wells; however, significant lattice and thermal mismatches exist between InGaN and the GaN barrier layer, easily leading to defects and dislocations during epitaxial growth. Furthermore, InGaN materials are prone to phase segregation at higher growth temperatures, which also reduces the thermal stability of the quantum well.

[0003] High-temperature p-type growth is generally considered the main cause of thermal decomposition in quantum wells. To obtain high-quality materials, p-type AlGaN confinement layers and p-type GaN contact layers require growth at temperatures above 1000 degrees Celsius, while the optimal growth temperature for green quantum wells is only around 600-700 degrees Celsius. This high thermal budget leads to the migration and diffusion of In atoms in the InGaN quantum well, resulting in well layer decomposition and a decrease in laser luminescence quality. Summary of the Invention

[0004] The purpose of this invention is to provide a gallium nitride-based laser with high thermal stability, good thermal stability, and excellent optoelectronic properties.

[0005] Another objective of this invention is to provide a method for fabricating a gallium nitride-based laser with high thermal stability, which has a low growth temperature and can suppress the thermal decomposition of the quantum well active region.

[0006] The technical problem solved by this invention is achieved by the following technical solution.

[0007] On one hand, embodiments of the present invention provide a gallium nitride-based laser with high thermal stability, comprising, from top to bottom, an n-face electrode, an n-type substrate layer, an n-type confinement layer, an n-type waveguide layer, a quantum well active region, a p-type waveguide layer, a p-type electron blocking layer, a p-type confinement layer, a p-type contact layer, and a p-face electrode; The n-faceted electrode is a Ti / Au metal electrode, i.e., an alloy of Ti and Au; the n-type substrate layer is unintentionally doped 150-200 μm GaN; the n-type confinement layer is 700-800 nm Al. 0.08 Ga 0.92The N and Si doping concentration is 3×10⁻⁶. 18 cm -3 The n-type waveguide layer is 200-300 nm In. 0.05 Ga 0.95 The N and Si doping concentration is 3×10⁻⁶. 17 cm -3 The active region of the quantum well employs two pairs of unintentionally doped In atoms. 0.24 Ga 0.76 The N and GaN layers have thicknesses of 2-3 nm and 10-12 nm, respectively; the p-type waveguide layer is 100-200 nm thick In. 0.04 Ga 0.96 The N and Mg doping concentration is 3 × 10⁻⁶. 17 cm -3 The p-type electron blocking layer is 10-20 nm Al. 0.20 Ga 0.80 The N and Mg doping concentration is 1×10⁻⁶. 19 cm -3 The p-type confinement layer is an Al₂O₃ with a wavelength of 400-500 nm. 0.08 Ga 0.92 The N and Mg doping concentration is 1×10⁻⁶. 19 cm -3 The p-type contact layer is 100-150 nm GaN with a Mg doping concentration of 2 × 10⁻⁶. 19 cm -3 The p-side electrode is a Ni / Au metal electrode, that is, an alloy of Ni and Au.

[0008] In one embodiment of the present invention, the n-type substrate layer is an unintentionally doped 200 μm GaN; the n-type confinement layer is an 800 nm Al. 0.08 Ga 0.92 The N and Si doping concentration is 3×10⁻⁶. 18 cm -3 The n-type waveguide layer is 300 nm In. 0.05 Ga 0.95 Ni material, Si doping concentration of 3×10⁻⁶ 17 cm -3 The active region of the quantum well is unintentionally doped with In. 0.24 Ga 0.76 The N and GaN layers have thicknesses of 3 nm and 12 nm, respectively; the p-type waveguide layer is a 200 nm In layer. 0.04 Ga 0.96 The N and Mg doping concentration is 3 × 10⁻⁶. 17 cm -3 The p-type electron blocking layer is 20 nm Al. 0.20 Ga0.80 The N and Mg doping concentration is 1×10⁻⁶. 19 cm -3 The p-type confinement layer is a 500 nm Al. 0.08 Ga 0.92 The N and Mg doping concentration is 1×10⁻⁶. 19 cm -3 The p-type contact layer is 150 nm GaN with a Mg doping concentration of 2 × 10⁻⁶. 19 cm -3 .

[0009] On the other hand, embodiments of the present invention provide a method for fabricating a gallium nitride-based laser with high thermal stability, comprising the following steps: Using conventional semiconductor fabrication processes, the n-face electrode is connected to the n-type substrate layer. Using epitaxy, an n-type confinement layer, an n-type waveguide layer, a quantum well active region, a p-type waveguide layer, a p-type electron blocking layer, a p-type confinement layer, and a p-type contact layer are sequentially grown on the n-type substrate layer. Then, using conventional semiconductor fabrication processes, the p-face electrode is connected to the p-type contact layer to obtain the gallium nitride-based laser. The growth temperature of the active region of the quantum well is 680℃, and the growth temperature of the p-type electron blocking layer, p-type confinement layer and p-type contact layer is 980℃.

[0010] In some embodiments of the present invention, the epitaxial method may employ MOCVD or MBE.

[0011] Compared with the prior art, the embodiments of the present invention have at least the following advantages or beneficial effects: The laser provided by this invention can suppress the thermal decomposition of the quantum well, improve the electro-optical conversion efficiency of the device, and exhibit high thermal stability and high performance. During fabrication, the electron blocking layer, p-type confinement layer, and p-type contact layer are grown at a temperature of 980°C, matching the growth temperature of the quantum well active region at 680°C. Compared to the traditional growth temperature of 940-1020°C, this laser exhibits higher electroluminescence (EL) intensity at a growth temperature of 980°C. This is because lowering the growth temperature reduces the thermal load on the quantum well, thereby suppressing its thermal decomposition and ensuring sufficient hole concentration. Attached Figure Description

[0012] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 Transmission electron microscopy (TEM) images of quantum well samples with p-type electron blocking layer, confinement layer and contact layer grown at a growth temperature of 1020 °C. Figure 2 The carbon (C) impurity concentration distribution in the p-type electron blocking layer, confinement layer, and contact layer at different growth temperatures; Figure 3 Electroluminescence (EL) spectra of lasers with p-type electron blocking layers, confinement layers, and contact layers at different growth temperatures; Figure 4 This is a schematic diagram of a gallium nitride-based laser.

[0014] Icons: 01-n-type surface electrode, 02-n-type substrate layer, 03-n-type confinement layer, 04-n-type waveguide layer, 05-quantum well active region, 06-p-type waveguide layer, 07-p-type electron blocking layer, 08-p-type confinement layer, 09-p-type contact layer, 10-p-type surface electrode. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0016] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to specific embodiments.

[0017] Example 1 As attached Figure 4 As shown, the gallium nitride-based laser of this embodiment is fabricated according to the following steps based on MOCVD epitaxial growth: 1: n-face electrode 01, wherein the n-face electrode 01 is a Ti / Au electrode, which can form good ohmic contact with GaN material; 2: n-type substrate layer 02, wherein the GaN homogeneous substrate 02 is a self-supporting GaN material with a thickness of 200 μm; the n-face electrodes are connected to the n-type substrate layer using conventional semiconductor fabrication processes; 3: n-type confinement layer 03 is fabricated on GaN substrate 02 using an epitaxial growth method. The n-type confinement layer 03 is an 800 nm Al₂O₃ substrate. 0.08 Ga 0.92 Ni material, Si doping concentration of 3×10⁻⁶ 18 cm -3 ; 4: n-type waveguide layer 04, which is fabricated on n-type confinement layer 03. The n-type waveguide layer 04 is Si-doped In. 0.05 Ga 0.95 Ni material, doping concentration of 3×10 17 cm -3 Its thickness is 300 nm; 5: The InGaN / GaN quantum well active region 05 is fabricated on the n-type waveguide layer 04. The InGaN / GaN quantum well active region 05 is unintentionally doped In. 0.24 Ga 0.76 The N / GaN material has two quantum wells, with the well layer being In. 0.24 Ga 0.76 The material is N, with a thickness of 3 nm, and the quantum barrier is GaN, with a thickness of 12 nm. 6: p-type waveguide layer 06, which is fabricated on the active region 05 of the InGaN / GaN quantum well, wherein the p-type waveguide layer 06 is Mg-doped In 0.04 Ga 0.96 Ni material, doping concentration of 3×10 17 cm -3 Its thickness is 200 nm; 7: p-type electron blocking layer 07, which is fabricated on p-type waveguide layer 06, wherein the p-type AlGaN electron blocking layer 07 is Mg-doped Al 0.20 Ga 0.80 Ni material, doping concentration of 1×10 19 cm -3 The thickness is 20 nm; 8: p-type confinement layer 08, which is fabricated on p-type AlGaN electron blocking layer 07, wherein the p-type confinement layer 08 is 500 nm Al 0.08 Ga 0.92 Ni material, Mg doping concentration 1×10 19 cm -3 ; 9: p-type contact layer 09, which is fabricated on p-type confinement layer 08. The p-type contact layer 09 is made of 150 nm GaN material with a Mg doping concentration of 2 × 10⁻⁶. 19 cm -3 ; 10: p-side electrode 10, which is fabricated on p-type contact layer 09. The p-side electrode 10 is a Ni / Au electrode, which can form a good ohmic contact with p-type GaN material.

[0018] During the epitaxial growth of the device, the quantum well active region is grown at a temperature of 680℃, while the p-type electron blocking layer, confinement layer, and contact layer are grown at a temperature of 980℃. This reduces the thermal decomposition of the quantum well active region and ensures the hole concentration in the p-type layer, thereby improving the laser's luminescence quality and electro-optical conversion efficiency. Figure 4 As shown, compared to lasers with p-type growth at a high temperature of 1020℃ and lasers with p-type layers grown at a lower temperature of 940℃, lasers with p-type layers grown at a temperature of 980℃ have the highest luminous intensity.

[0019] Compared to traditional GaN-based laser structures, this invention reduces the growth temperature of the electron blocking layer, p-type confinement layer, and p-type contact layer to 980°C. Typically, to ensure the incorporation of In atoms in the quantum well active region, a growth temperature of around 680°C is used, while the growth temperatures of the n-type and p-type waveguide layers are slightly higher, around 740°C. The n-type substrate layer, electron blocking layer, p-type confinement layer, and p-type contact layer are located far from the quantum well active region; therefore, to improve material quality, growth temperatures of 1020°C or higher are typically used. The n-face electrodes and p-face electrodes are fabricated using electron beam evaporation at a growth temperature of 300°C.

[0020] From the appendix Figure 1 It can be concluded that when the growth temperature of the electron blocking layer, p-type confinement layer, and p-type contact layer is above 1020℃, obvious In clusters and well layer interruptions will occur in the quantum well, indicating that high temperature causes atomic migration in the InGaN quantum well, resulting in thermal decomposition. However, when the growth temperature of the electron blocking layer, p-type confinement layer, and p-type contact layer is reduced to below 940℃, more carbon impurities will be incorporated into this layer during growth, such as... Figure 2 As shown, the compensating effect of carbon impurities leads to a decrease in hole concentration and an increase in resistivity in this layer (Hall test results show that when the growth temperature of the p-type confinement layer and contact layer decreases from 1020℃ to 940℃, the hole concentration in this layer increases from 1.85×10⁻⁶). 17 cm -3 Reduced to 1.32×10 16 cm -3 The resistivity increased significantly from 1.68 Ω / cm to 52.8 Ω / cm, which is detrimental to improving the electrical performance of the laser.

[0021] like Figure 3 As shown, the electroluminescence spectra of lasers prepared at different growth temperatures show that the laser exhibits the strongest electroluminescence intensity at a growth temperature of 980℃.

[0022] in, Figure 2 and Figure 3In the figure, the growth temperature of the p-type electron blocking layer, confinement layer and contact layer of the pGaN-940 laser is 940℃, the growth temperature of the p-type electron blocking layer, confinement layer and contact layer of the pGaN-980 laser is 980℃, and the growth temperature of the p-type electron blocking layer, confinement layer and contact layer of the pGaN-940 laser is 1020℃.

[0023] The embodiments described above are some, but not all, embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A gallium nitride-based laser with high thermal stability, characterized in that, It includes, from top to bottom, an n-face electrode, an n-type substrate layer, an n-type confinement layer, an n-type waveguide layer, a quantum well active region, a p-type waveguide layer, a p-type electron blocking layer, a p-type confinement layer, a p-type contact layer, and a p-face electrode; The n-faceted electrode is a Ti / Au metal electrode; The n-type substrate layer is an unintentionally doped 150-200 μm GaN; the n-type confinement layer is a 700-800 nm Al0.08Ga0.92N with a Si doping concentration of 3 × 10¹⁸ cm⁻³; the n-type waveguide layer is a 200-300 nm In0.05Ga0.95N with a Si doping concentration of 3 × 10¹⁷ cm⁻³; the quantum well active region uses unintentionally doped In0.24Ga0.76N and GaN with thicknesses of 2-3 nm and 10-12 nm, respectively; the p-type waveguide layer is a 100-200 nm In0.04Ga0.96N with a Mg doping concentration of 3 × 10¹⁷ cm⁻³; the p-type electron blocking layer is a 10-20 nm Al0.20Ga0.80N with a Mg doping concentration of 1 × 10¹⁹ cm⁻³; the p-type confinement layer is a 400-500 nm... The p-type contact layer is made of 100-150 nm Al0.08Ga0.92N with a Mg doping concentration of 1×10¹⁹ cm⁻³; the p-type contact layer is made of 100-150 nm GaN with a Mg doping concentration of 2×10¹⁹ cm⁻³; the p-side electrode is a Ni / Au metal electrode.

2. The gallium nitride-based laser with high thermal stability according to claim 1, characterized in that, The n-type substrate layer is an unintentionally doped 200 μm GaN; the n-type confinement layer is an 800 nm Al0.08Ga0.92N; the n-type waveguide layer is a 300 nm In0.05Ga0.95N; the thicknesses of the In0.24Ga0.76N and GaN active regions of the quantum well are 3 nm and 12 nm, respectively; the p-type waveguide layer is a 200 nm In0.04Ga0.96N; the p-type electron blocking layer is a 20 nm Al0.20Ga0.80N; the p-type confinement layer is a 500 nm Al0.08Ga0.92N; and the p-type contact layer is a 100-150 nm GaN.

3. A method for fabricating a gallium nitride-based laser with high thermal stability as described in claim 1 or 2, characterized in that, Includes the following steps: Connect the n-face electrodes to the n-type substrate layer; An epitaxial growth method is used to sequentially grow an n-type confinement layer, an n-type waveguide layer, a quantum well active region, a p-type waveguide layer, a p-type electron blocking layer, a p-type confinement layer, and a p-type contact layer on an n-type substrate; then, the p-side electrode is connected to the p-type contact layer to obtain the gallium nitride-based laser. The growth temperature of the active region of the quantum well is 680℃, and the growth temperature of the p-type electron blocking layer, p-type confinement layer and p-type contact layer is 980℃.

4. The method for fabricating a gallium nitride-based laser with high thermal stability according to claim 3, characterized in that, The epitaxial method is MOCVD or MBE.

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