A gallium nitride-based laser epitaxial structure and a laser having the same

Abstract

The application discloses a gallium nitride-based laser epitaxial structure and a laser with the structure, and relates to the field of semiconductor optoelectronic devices. The gallium nitride-based laser epitaxial structure is designed by designing the active region structure and the epitaxial growth method of the gallium nitride-based laser, so that the crystal quality of the active region and the carrier injection efficiency to the active region are effectively improved. Meanwhile, by designing a new light waveguide layer structure and a growth method, the internal loss is effectively reduced on the basis of improving the light field restriction effect. In addition, other layer structures of the gallium nitride-based laser epitaxial structure are further designed, so that the light field restriction effect is further improved, and the internal loss of the laser is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor optoelectronic devices, and more particularly, to a gallium nitride-based laser epitaxial structure and a laser having the same. BACKGROUND

[0002] III-V nitride semiconductor materials are ideal materials for making semiconductor lasers from ultraviolet to green light bands. GaN-based green laser is one of the three primary colors of light sources for laser display, and has great scientific research value, economic value and market prospect.

[0003] In recent years, great progress has been made in the research of gallium nitride-based semiconductor lasers in China. The output power, threshold current density and operating voltage of blue-green lasers have approached or reached the international advanced level. However, there are still deficiencies in the design of laser structure and the optimization of growth method, such as high quantum efficiency stress regulation active region, new superlattice optical waveguide layer and new optical confinement layer, which lead to the problems of low quantum efficiency of active region, small optical field confinement factor and large internal loss of laser.

[0004] The prior art discloses a gallium nitride-based laser diode epitaxial structure and a preparation method thereof. By designing a gradually changing In component trapezoidal active region structure, a new gallium nitride-based laser diode epitaxial structure is obtained. When the laser is used for optical pumping, the full width at half maximum is narrow and the beam quality is high. However, the active region is mainly grown by constant temperature or linear temperature variation during the growth process, and the quantum efficiency of the active region still needs to be improved. SUMMARY

[0005] In order to overcome the defects and deficiencies of low quantum efficiency of the active region and low optical power in the prior art, the present application provides a gallium nitride-based laser epitaxial structure. By designing the quantum well active region structure and the epitaxial growth method, the quantum efficiency of the active region is effectively improved.

[0006] Another object of the present application is to provide a gallium nitride-based laser having the above structure.

[0007] The above objects of the present application are achieved by the following technical solutions.

[0008] A gallium nitride-based laser epitaxial structure, comprising, from bottom to top, a GaN single crystal substrate 101, an n-type GaN layer 102, an n-type confinement layer 103, an n-type lower waveguide layer 104, an active region 105, an upper waveguide layer 106, an electron blocking layer 107, a p-type GaN upper waveguide layer 108, a p-type confinement layer 109 and a p-type contact layer 110.

[0009] The active region is an asymmetric InGaN / GaN double quantum well structure, and from bottom to top, a first InGaN barrier layer, a first InGaN well layer, a second GaN barrier layer, a second InGaN well layer and an InGaN last barrier layer are sequentially stacked.

[0010] The thickness of the first InGaN well layer and the second InGaN well layer of the active region is 2-6nm, and a step-by-step growth method is adopted, that is, first growing 0.5-1nm at 700-800℃, then performing recrystallization treatment at 780-850℃, and repeating the growth for 3-12 cycles to obtain the InGaN well layer.

[0011] It should be noted that:

[0012] In the traditional GaN-based laser epitaxial structure, the lattice mismatch between the InGaN quantum well (i.e. well layer) and the GaN barrier layer in the active region is large, which causes a large stress and thus generates a high density of interface defects, which seriously affects the quantum efficiency of the InGaN / GaN quantum well, and further reduces the optical power. In addition, the In-rich clusters on the surface of the InGaN quantum well are also the main cause of the formation of interface defects.

[0013] The present application provides a certain temperature by a special step-by-step growth method, so that the InGaN well layer grows smoothly to a certain thickness, and then the temperature is increased to a certain range to perform high-temperature recrystallization treatment on the InGaN well layer, which improves the migration ability of atoms on the material surface and ensures that the atoms can fall to the lowest point when migrating on the lattice surface, thereby reducing the generation of interface defects.

[0014] At the same time, the growth thickness of the InGaN well layer needs to be controlled during the growth process to avoid excessive growth thickness and a large number of atom growth layers, which increases the internal defects of the crystal and causes the defects to be unable to be repaired during the subsequent high-temperature recrystallization treatment.

[0015] During the step-by-step growth process, the temperature of the recrystallization treatment is higher than the growth temperature.

[0016] The first barrier layer of the active region is a heavily n-doped GaN layer. + The InGaN structure, wherein, n + The thickness of the InGaN is 5-15nm, the growth temperature is 800-950℃, the In content is the same as that of the lower waveguide layer, the n-type doping source is Si, and the Si doping concentration is 10 18 -10 19 cm -3 ; the thickness of the second GaN barrier layer is 3-10nm, the growth temperature is 800-950℃; the thickness of the InGaN last barrier layer is 3-10nm, the growth temperature is 800-950℃, and the In content is the same as that of the upper waveguide layer.

[0017] Specifically, a low-temperature GaN protective layer is inserted between the first InGaN well layer and the second GaN barrier layer of the active region, and between the second InGaN well layer and the InGaN last barrier layer.

[0018] The low-temperature GaN protective layer is a GaN layer, and adding a thin low-temperature GaN protective layer can effectively protect the InGaN quantum well that has been grown, avoiding atomic migration again during subsequent high-temperature growth of the barrier layer, resulting in the generation of defects.

[0019] Specifically, the first InGaN well layer and the second InGaN well layer of the active region are In x2 Ga 1-x2 N well layers, where 0.05≤x2≤0.30.

[0020] The application limits the specific In content in the InGaN well layer, improves the ratio of group V / group III, and further reduces the interface defect density.

[0021] The specific growth method of each layer of the active region is as follows: the first In x2 Ga 1-x2 N well layer is grown by a step-by-step method, 0.5-1 nm (1-2 atomic layer thickness) of the InGaN well layer is first grown, then the Ga source is stopped from being introduced into the reaction chamber, the In source, NH3 and N2 are kept being introduced into the reaction chamber, decomposition of the quantum well is inhibited, the temperature is increased to 780-850℃ under the above conditions, recrystallization treatment of the quantum well is performed for 5-60 s, then the temperature is decreased to 750-800℃, 0.5-1 nm of the InGaN well layer is continuously grown, continuous recrystallization treatment is performed, 2-6 nm of the InGaN well layer is obtained through 3-12 cycles of repeated growth, then the low-temperature GaN protective layer is continuously grown at 750-800℃, the temperature is increased to 800-950℃ to grow the second GaN barrier layer, the barrier layer has a thickness of 3-10 nm; then the second InGaN well layer is continuously grown by the step-by-step method, 0.5-1 nm is first grown at 750-800℃, recrystallization treatment is performed at 780-850℃, and 3-12 cycles of repeated growth are performed. On this basis, the low-temperature GaN protective layer is grown at 750-800℃, and the InGaN last barrier layer is grown by increasing the temperature to 800-950℃.

[0022] Specifically, the growth thickness of the n-type GaN layer 102 is 1-5 μm, the growth temperature is 1000-1100℃, the n-type doping source Si doping concentration is 10 18 ~10 19 cm -3 .

[0023] Specifically, the n-type confinement layer 103 is n-Al y1 Ga 1-y1 N / GaN superlattice light confinement layer, wherein n-Al y1 Ga 1- y1 N has a thickness of 2-7 nm, and the Al component satisfies 0.01≤y1≤0.2.

[0024] By controlling the Al component of the n-type AlGaN confinement layer and adjusting the thickness of the n-type AlGaN confinement layer, the light field confinement effect is enhanced, the light field leakage is suppressed, the overlap of the light field with the p-type layer is reduced, and thus the optical loss is reduced.

[0025] The n-Al y1 Ga 1-y1 N / GaN superlattice light confinement layer has a superlattice period number of 100-150, and the n-type doping source has a Si doping concentration of 10 18 ~10 19 cm -3 , and the GaN has a thickness of 2-5 nm.

[0026] Adjusting the Si doping concentration of the n-type doping source is beneficial to further reducing the overlap with the p-type layer and reducing the loss.

[0027] Specifically, the n-type lower waveguide layer 104 is n-GaN+n-In x1 Ga 1-x1 N composite waveguide layer, wherein n-In x1 Ga 1- x1 N is grown at a temperature of 800-900 ℃ to a thickness of 10-20 nm, then the metal organic source is stopped from being introduced into the reaction chamber, NH3 and N2 are kept being introduced into the reaction chamber, the growth temperature is increased to 850-950 ℃, and the In x1 Ga 1-x1 N waveguide layer is subjected to high-temperature recrystallization, and the In x1 Ga 1-x1 N waveguide layer is repeatedly grown for 3-15 cycles to a thickness of 50-150 nm; wherein x1 x1 Ga 1-x1 N waveguide layer; wherein x1

[0028] Specifically, the In x1 Ga 1-x1 N waveguide layer has an In component satisfying 0.01≤x1≤0.10, and smaller than the In component in the active region well layer, i.e., x1

[0029] The n-type lower waveguide layer 104 contains n-GaN with a thickness of 10–250 nm, grown at a temperature of 850–1050 °C, and the doping concentration of the n-type doped source Si is 1 × 10⁻⁶. 17 cm -3 ~5×10 18 cm -3 .

[0030] In x1 Ga 1-x1 During the growth of the N-waveguide layer, the thickness of each growth step is controlled to avoid excessive increase in defect density. By introducing a high-temperature recrystallization process and controlling the recrystallization temperature, inward diffusion (diffusion into the crystal lattice) and surface desorption rearrangement of atoms can be achieved during the growth process, forming a more stable thermodynamic state. This helps to repair defects generated during further crystal growth and improve the crystal quality of the waveguide layer.

[0031] Meanwhile, using InGaN instead of GaN as the waveguide layer can effectively improve the optical field confinement factor, reduce light leakage, and further improve the optical power of the laser.

[0032] Specifically, the upper waveguide layer 106 is an undoped InGaN upper waveguide layer, i.e., u-In x3 Ga 1-x3 N was grown using a stepwise growth method, first growing In with a thickness of 10–20 nm at 800–900 °C. x3 Ga 1-x3 N, then at 850–950℃, In x3 Ga 1- x3 The N-waveguide layer undergoes high-temperature recrystallization, and the In is obtained through 3–15 cycles of repeated growth. x3 Ga 1-x3 The thickness of the N-waveguide layer is 50–150 nm; where x3 < x2.

[0033] Specifically, the In x3 Ga 1-x3 The In component of the N waveguide layer satisfies 0.01≤x3≤0.10 and is less than the In component in the active region trap layer, i.e., x3<x2.

[0034] By adjusting In x1 Ga 1-x1 N-lower waveguide layer, In x3 Ga 1-x3 The In composition in the waveguide layer on N can further improve the crystal quality.

[0035] Specifically, the electron blocking layer 107 is a p-type AlGaN electron blocking layer with a thickness of 5–25 nm and an Al content of 5–25%.

[0036] The growth temperature of the p-type AlGaN electron blocking layer is 900-980℃.

[0037] Specifically, the growth temperature of the p-type GaN upper waveguide layer 108 is 850-1050℃, and the thickness is 10-250nm, wherein the doping concentration of the p-type doping source Mg is 10 17 -10 18 cm -3 .

[0038] The upper waveguide layer 106 and the p-type GaN upper waveguide layer 108 jointly constitute the p-type waveguide layer of the laser, i.e. the p-type upper waveguide layer is a u-In x3 Ga 1-x3 N+p-GaN composite structure, and the p-type AlGaN electron blocking layer 107 is inserted between the u-In x3 Ga 1-x3 N and the p-GaN.

[0039] The u-In x3 Ga 1-x3 N is grown by a step-by-step growth method, and a layer of In x3 Ga 1-x3 N with a thickness of 10-20nm is first grown at a growth temperature of 800-900℃, then the metal organic source is stopped from being introduced into the reaction chamber while NH3 and N2 are kept being introduced into the reaction chamber, the growth temperature is increased to 850-950℃ to perform high-temperature recrystallization on the In x3 Ga 1-x3 N waveguide layer, then the growth temperature is decreased to 800-900℃, and the In x3 Ga 1-x3 N waveguide layer with a thickness of 10-20nm is continuously grown, and high-temperature recrystallization is performed again, and the In x3 Ga 1-x3 N waveguide layer is repeatedly grown for 3-15 cycles, on the basis of which the p-type AlGaN electron blocking layer 107 is grown, and then the p-type GaN upper waveguide layer 108 is continuously grown at 850-1050℃.

[0040] The u-In x3 Ga 1-x3 N is grown by a step-by-step growth method, and the corresponding temperature and growth thickness are controlled, so as to reduce crystal defects, and control the migration rate and diffusion direction of atoms in the growth process, thereby improving the crystal quality.

[0041] The undoped InGaN layer is inserted between the active region and the electron blocking layer, so as to separate the p-type layer from the active region, thereby improving the light confinement factor of the active region and reducing optical loss.

[0042] By adjusting the thickness of the non-In-doped GaN layer and the Mg concentration distribution, the optical loss is further reduced.

[0043] Specifically, the p-type confinement layer 109 is a p-Al y2 Ga 1-y2 N / GaN superlattice optical confinement layer, wherein Al y2 Ga 1-y2 N thickness is 2-5 nm, and 0.01<=y2<=0.15.

[0044] By appropriately increasing the Al component of the p-type AlGaN confinement layer and increasing the thickness of the p-type AlGaN confinement layer, the optical field in the laser can be moved to the p-type side, the overlap with the n-type layer is reduced, and the loss is reduced.

[0045] Specifically, the p-Al y2 Ga 1-y2 N / GaN superlattice optical confinement layer has a superlattice period of 100-150, and a p-type doping source Mg doping concentration of 10 17 ~10 18 cm -3 , and a GaN thickness of 2-5 nm.

[0046] Adjusting the p-type doping source Mg doping concentration is beneficial to further reduce the overlap with the n-type layer and reduce the loss.

[0047] Specifically, the p-type contact layer 110 is a p-type GaN layer with a thickness of 100-150 nm and a Mg doping concentration of 10 17 ~10 18 cm -3 .

[0048] The application provides a growth method of the above-mentioned GaN-based laser epitaxial structure, comprising the following steps:

[0049] S1. Activating the GaN single crystal substrate under the condition of a mixed atmosphere of hydrogen and ammonia and a temperature of 1000-1100 DEG C;

[0050] S2. Growing an n-type GaN layer on the GaN single crystal substrate by inputting III group sources, V group sources and n-type doping sources under the condition of a hydrogen atmosphere and a temperature of 1000-1100 DEG C;

[0051] S3. Growing an n-type confinement layer on the n-type GaN layer by inputting III group sources, V group sources and n-type doping sources under the condition of a hydrogen atmosphere and a temperature of 1000-1100 DEG C;

[0052] S4. Growing an n-type lower waveguide layer on the n-type confinement layer by inputting III group sources, V group sources and n-type doping sources under the condition of a nitrogen atmosphere and a temperature of 800-1050 DEG C;

[0053] S5. Growing the active region on the n-type lower waveguide layer by introducing the group III source and the group V source under the temperature of 800-950℃ in the nitrogen atmosphere;

[0054] S6. Growing the upper waveguide layer, the electron blocking layer and the p-type GaN upper waveguide layer on the active region in sequence by introducing the group III source, the group V source and the p-type doping source under the temperature of 800-1050℃ in the nitrogen atmosphere;

[0055] S7. Growing the p-type confinement layer by introducing the group III source, the group V source and the p-type doping source under the temperature of 850-1050℃ in the hydrogen atmosphere;

[0056] S8. Growing the p-type contact layer by introducing the group III source, the group V source and the p-type doping source under the temperature of 850-1050℃ in the hydrogen atmosphere.

[0057] After the epitaxial growth of the GaN-based laser epitaxial structure is completed, the temperature of the reaction chamber is reduced to 750℃, and the pure nitrogen atmosphere is used for annealing treatment for 20 minutes, and then the temperature is reduced to room temperature, and the growth is completed.

[0058] Specifically, in the step S2, trimethyl gallium, trimethyl aluminum and trimethyl indium are introduced as the group III source, ammonia is introduced as the group V source, and SiH4 is introduced as the n-type doping source; in the step S3, trimethyl gallium, trimethyl aluminum and trimethyl indium are introduced as the group III source, ammonia is introduced as the group V source, and SiH4 is introduced as the n-type doping source; in the step S4, trimethyl gallium, trimethyl aluminum and trimethyl indium are introduced as the group III source, ammonia is introduced as the group V source, and SiH4 is introduced as the n-type doping source; in the step S5, trimethyl gallium, trimethyl aluminum and trimethyl indium are introduced as the group III source, and ammonia is introduced as the group V source; in the step S6, trimethyl gallium, trimethyl aluminum and trimethyl indium are introduced as the group III source, ammonia is introduced as the group V source, and dimethyl magnesium is introduced as the p-type doping source; in the step S7, trimethyl gallium and trimethyl aluminum are introduced as the group III source, ammonia is introduced as the group V source, and dimethyl magnesium is introduced as the p-type doping source; in the step S8, trimethyl gallium is introduced as the group III source, ammonia is introduced as the group V source, and dimethyl magnesium is introduced as the p-type doping source.

[0059] Specifically, the activation treatment time in the step S1 is 5-10 minutes, the time in the step S2 is 10-30 minutes, the time in the step S3 is 15-60 minutes, the time in the step S4 is 15-60 minutes, the time in the step S5 is 5-30 minutes, and the time in the step S6 is 15-60 minutes.

[0060] Specifically, the steps S1-S6 are performed in the metal organic compound vapor phase epitaxy reaction chamber.

[0061] Specifically, hydrogen is first introduced in the step S1, and after being heated to 500 DEG C, ammonia is introduced,

[0062] The unexplained structure or growth parameters of the application can be selected according to the conventional conditions in the art.

[0063] The application particularly protects a gallium nitride-based laser, which contains the gallium nitride-based laser epitaxial structure described above.

[0064] The application designs the active region structure and the epitaxial growth method of the gallium nitride laser, obtains a new gallium nitride-based laser epitaxial structure, and the gallium nitride-based laser epitaxial structure is used in a laser, which can effectively improve the optical power of the laser and reduce the internal loss of the laser.

[0065] Compared with the prior art, the application has the following beneficial effects:

[0066] The application provides a gallium nitride-based laser epitaxial structure, which is designed by designing the active region structure and the epitaxial growth method of the gallium nitride laser, effectively improves the active region crystal quality and the carrier injection efficiency into the active region, and meanwhile, by designing a new optical waveguide layer structure and a growth method, the internal loss is effectively reduced on the basis of improving the optical field restriction effect. In addition, the application further designs other layer structures of the gallium nitride-based epitaxial structure, further improves the optical field restriction effect, and reduces the internal loss of the laser.

[0067] The gallium nitride-based laser epitaxial structure can effectively improve the quantum efficiency of the active region, improve the optical power of the laser, and obtain a laser with an optical power of 30 mW under a 30 mA injection current. BRIEF DESCRIPTION OF DRAWINGS

[0068] Figure 1 It is a structure schematic diagram of the gallium nitride-based laser epitaxial structure of Example 1.

[0069] Figure 2 It is a curve of the optical power and the working voltage of the gallium nitride laser epitaxial structure of Example 1 and Comparative Example 1 varying with an injection current.

[0070] Figure 3 It is an optical field distribution diagram of the gallium nitride-based laser epitaxial structure of Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0071] The raw materials in the examples can be obtained by marketing;

[0072] The Aixtron company, a tight coupling vertical reaction chamber MOCVD growth system, is used in the preparation process of the examples and the comparative examples of the application.

[0073] The present invention will be further described below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise stated, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents.

[0074] Example 1

[0075] An epitaxial structure for a gallium nitride-based laser, such as Figure 1 As shown, from bottom to top, a gallium nitride single crystal substrate 101, an n-type GaN layer 102, and an n-type Al layer are stacked sequentially. y1 Ga 1-y1 103 N / GaN superlattice optical confinement layer, 104 n-type GaN+n-type InGaN composite lower waveguide layer, 105 active region, 106 undoped InGaN upper waveguide layer, 107 p-type AlGaN electron blocking layer, 108 p-type GaN upper waveguide layer, 109 p-type AlGaN / GaN superlattice confinement layer, and 110 p-type GaN contact layer.

[0076] The n-type GaN layer has a thickness of 3 μm, a growth temperature of 1050℃, and an n-type doping source Si doping concentration of 10. 18 cm -3 ;

[0077] The n-type Al y1 Ga 1-y1 The N / GaN superlattice optical confinement layer 103 has a superlattice period number of 150, and n-type Al y1 Ga 1- y1 The AlGaN thickness in the N / GaN superlattice is 2.5 nm, and the Al composition is... y1 The Si doping concentration is 0.15, the GaN thickness is 2.5 nm, and the n-type doped source Si doping concentration is 5 × 10⁻⁶. 18 cm -3 ;

[0078] In the n-type GaN+n-type InGaN composite waveguide layer 104, the thickness of the n-type GaN is 100 nm, the growth temperature is 1050 °C, and the Si doping concentration of the n-type doped source is 1 × 10⁻⁶. 17 cm -3 The n-type InGaN is an n-type In 0.025 Ga 0.975 N was grown using a stepwise growth method, firstly at a growth temperature of 850℃, with a thickness of 10 nm. 0.025 Ga 0.975 N, then increase the growth temperature to 900℃ for In 0.025 Ga 0.975 The N-waveguide layer is recrystallized at high temperature, and then the growth temperature is lowered to 850℃ to continue growing an In layer with a thickness of 10 nm.0.025 Ga 0.975 N waveguide layer, and then high-temperature recrystallization is performed, and through 5 cycles of repeated growth, an In 0.025 Ga 0.975 N waveguide layer structure; wherein the In component x1 is 0.025, which is less than the In component in the active region well layer, and the Si doping concentration is 2×10 18 cm -3 ;

[0079] The active region is an asymmetric InGaN / GaN double quantum well structure, and from bottom to top, a first In 0.025 Ga 0.975 N barrier layer, a first In 0.18 Ga 0.82 N well layer, a second GaN barrier layer, a second In 0.18 Ga 0.82 N well layer and an In 0.025 Ga 0.975 N final barrier layer are sequentially stacked; the active region first barrier layer is a heavily doped n + -InGaN structure, wherein the n + -InGaN thickness is 10 nm, the n-type doping source Si doping concentration is 1×10 18 cm -3 , the growth temperature is 800-950 ℃, the In component is the same as the In component of the lower waveguide layer; the first In x2 Ga 1-x2 N well layer thickness is 3 nm, the In component x2=0.18, the growth temperature is 750 ℃, the InGaN well layer is grown by a step-by-step method, 0.5 nm thick InGaN well layer is first grown, then the Ga source is stopped from being introduced into the reaction chamber, the In source, NH3 and N2 are kept from being introduced into the reaction chamber, the quantum well decomposition is inhibited, the temperature is increased to 780 ℃ under this condition, the quantum well is recrystallized for 5 seconds, then the temperature is decreased to 750 ℃, 0.5 nm of InGaN well layer is continuously grown, and the recrystallization treatment is continuously performed, through 6 cycles of repeated growth, the InGaN well layer with a thickness of 3 nm is obtained, then a low-temperature GaN protective layer is grown at 750 ℃, the temperature is increased to 850 ℃ to grow a second GaN barrier layer, and the barrier layer thickness is 10 nm; then the second In 0.18 Ga 0.82 N well layer is grown by a step-by-step method, and the thickness is 3 nm, wherein the specific process flow is the same as that of the first InGaN well layer, on this basis, a low-temperature GaN protective layer is grown at 750 ℃, the temperature is increased to 850 ℃ to grow a final InGaN barrier layer, and the barrier layer thickness is 10 nm, wherein the In component is the same as the In component of the upper waveguide layer;

[0080] The upper waveguide layer is u-In 0.025 Ga 0.975 N (non-In-doped InGaN upper waveguide layer 106) + p-GaN composite structure, as a p-type waveguide layer of a laser diode, in u-In 0.025 Ga 0.975 N and p-GaN, a p-AlGaN electron blocking layer is inserted. Among them, u-In 0.025 Ga 0.975 The InGaN upper waveguide layer is grown by a step-by-step method, with a total thickness of 50 nm, and the specific process is the same as that of the InGaN lower waveguide layer, except that it is grown for 10 nm each time, and 5 cycles of growth are performed; on this basis, a p-AlGaN electron blocking layer is grown at 950°C, with an Al component of 20% and a thickness of 20 nm, and then a p-GaN waveguide layer is grown at 950°C, with a p-type dopant source Mg doping concentration of 2×10 17 cm -3 ;

[0081] The p-type confinement layer is a p-Al y2 Ga 1-y2 N / GaN superlattice light confinement layer, with a superlattice period of 100, an AlGaN thickness of 2.5 nm in the superlattice, a GaN thickness of 2.5 nm, an Al component satisfying y2=0.15, and a p-type dopant source Mg doping concentration of 2×10 17 cm -3 .

[0082] The p-type GaN layer has a thickness of 100 nm and a p-type dopant source Mg doping concentration of 2×10 17 cm -3 .

[0083] A schematic diagram of the gallium nitride-based laser epitaxial structure is as Figure 1 .

[0084] Example 2

[0085] A gallium nitride-based laser epitaxial structure has the same structure as Example 1, except that:

[0086] The first InGaN well layer and the second InGaN well layer of the active region have a thickness of 6 nm, are grown for 1 nm each time, and are repeatedly grown for 6 cycles to obtain the InGaN well layer.

[0087] Example 3

[0088] A gallium nitride-based laser epitaxial structure has the same structure as Example 1, except that it is first grown at 800°C and then subjected to a recrystallization treatment at 850°C.

[0089] Example 4

[0090] A GaN-based laser epitaxial structure, the structure is the same as that of Example 1, except that no low-temperature GaN protective layer is inserted between the first InGaN well layer and the second GaN barrier layer of the active region, and between the second InGaN well layer and the last InGaN barrier layer of the active region.

[0091] Example 5

[0092] A GaN-based laser epitaxial structure, the structure is the same as that of Example 1, except that the first InGaN well layer and the second InGaN well layer of the active region are In 0.05 Ga 0.95 N well layers.

[0093] Example 6

[0094] A GaN-based laser epitaxial structure, the structure is the same as that of Example 1, except that the first InGaN well layer and the second InGaN well layer of the active region are In 0.3 Ga 0.7 N well layers.

[0095] Example 7

[0096] A GaN-based laser epitaxial structure, the structure is the same as that of Example 1, except that the lower waveguide layer n-In 0.025 Ga 0.975 N is first grown at 900°C to a thickness of 20 nm, then high-temperature recrystallization is performed at 950°C, and the In 0.025 Ga 0.975 N waveguide layer is repeatedly grown for 7 cycles to a thickness of 140 nm.

[0097] Example 8

[0098] A GaN-based laser epitaxial structure, the structure is the same as that of Example 1, except that the upper waveguide layer u-In 0.025 Ga 0.975 N is first grown at 900°C to a thickness of 20 nm, then high-temperature recrystallization is performed at 950°C, and the In 0.025 Ga 0.975 N waveguide layer is repeatedly grown for 7 cycles to a thickness of 140 nm.

[0099] Example 9

[0100] A GaN-based laser epitaxial structure, the structure is the same as that of Example 1, except that the n-Al y1 Ga 1-y1 N thickness of the n-type confinement layer 103 is 7 nm, and y1=0.2.

[0101] Example 10

[0102] A method for growing a gallium nitride-based epitaxial structure according to Embodiments 1-9, comprising the following steps:

[0103] S1. First, in a metal organic compound vapor phase epitaxy reaction chamber, under a hydrogen atmosphere, the temperature is raised to 300°C, NH3 is introduced into the reaction chamber, and then the temperature is raised to 1050°C. Under a mixed atmosphere of hydrogen (H2) and ammonia (NH3), the temperature is 1050°C. The surface of a GaN substrate is activated for 10 minutes;

[0104] S2. Under a hydrogen (H2) atmosphere, on the GaN substrate obtained in step S1, the temperature is 1000-1100°C. Trimethyl gallium is introduced as a group III source, NH3 is introduced as a group V source, and SiH4 is introduced as an n-type doping source. An n-type GaN layer is grown on the GaN substrate;

[0105] S3. Under a hydrogen (H2) atmosphere, at 1050°C, trimethyl gallium, trimethyl aluminum, and trimethyl indium are introduced as group III sources, NH3 is introduced as a group V source, and SiH4 is introduced as an n-type doping source. An n-type confinement layer is grown on the n-type GaN layer;

[0106] S4. Under a nitrogen atmosphere, at a temperature of 850-1050°C, trimethyl gallium, trimethyl indium, and trimethyl aluminum are introduced as group III sources, ammonia is introduced as a group V source, and SiH4 is introduced as an n-type doping source. A lower waveguide layer is grown on the n-type confinement layer;

[0107] S5. Under a nitrogen atmosphere, at a temperature of 750-950°C, trimethyl gallium is introduced as a group III source, and ammonia is introduced as a group V source. An active region is grown on the lower waveguide layer;

[0108] S6. Under a nitrogen atmosphere, at a temperature of 850-1050°C, trimethyl gallium, trimethyl indium, and trimethyl aluminum are introduced as group III sources, ammonia is introduced as a group V source, and dimethyl magnesium is introduced as a p-type doping source. An upper waveguide layer, an electron blocking layer, and a p-type GaN upper waveguide layer are sequentially grown on the active region;

[0109] S7. Under a hydrogen atmosphere, at a temperature of 950°C, trimethyl gallium and trimethyl aluminum are introduced as group III sources, ammonia is introduced as a group V source, and dimethyl magnesium is introduced as a p-type doping source. A p-type confinement layer is grown;

[0110] S8. Under a hydrogen atmosphere, at a temperature of 950°C, trimethyl gallium is introduced as a group III source, ammonia is introduced as a group V source, and dimethyl magnesium is introduced as a p-type doping source. A p-type contact layer is grown;

[0111] The temperature in the steps S4-S6 is selected according to the specific growth conditions of each layer in Embodiments 1-3, and the temperature when the Group III source, the Group V source, and the doping source are introduced is the temperature for the first growth of each layer.

[0112] After the epitaxial growth of the GaN-based laser epitaxial structure is completed, the temperature of the reaction chamber is reduced to 750°C, annealing treatment is performed for 20 min in a pure nitrogen atmosphere, and then the temperature is reduced to room temperature, the growth is completed, and the GaN-based laser epitaxial structure is obtained.

[0113] Comparative Example 1

[0114] A GaN-based laser epitaxial structure, which is different from that of Embodiment 1 in that the structures of the lower waveguide layer 104, the active region 105, and the upper waveguide layer 106 are different.

[0115] The specific structures and growth methods of the lower waveguide layer, the active region, and the upper waveguide layer of Comparative Example 1 are as follows:

[0116] Under a nitrogen (N2) atmosphere, trimethylgallium is introduced as the Group III source, NH3 is introduced as the Group V source, and SiH4 is introduced as the n-type doping source to grow the lower waveguide layer on the n-type confinement layer at 850°C.

[0117] The lower waveguide layer is an undoped GaN waveguide layer with a thickness of 100 nm and a growth temperature of 850°C.

[0118] Under a nitrogen (N2) atmosphere, trimethylindium is introduced as the Group III source, and NH3 is introduced as the Group V source to grow the active region on the lower waveguide layer.

[0119] The active region adopts an InGaN / GaN double quantum well structure, wherein the InGaN / GaN double quantum well structure of the active region has an InGaN well layer and a GaN barrier layer. x Ga 1-x The GaN well layer is grown at a constant temperature of 750°C, the growth thickness is 3 nm, the In component x = 0.15, the total thickness of the GaN in the middle barrier layer is 10 nm, and the GaN barrier layer is grown at a constant temperature of 850°C.

[0120] Under a nitrogen atmosphere, trimethylgallium and trimethylindium are introduced as the Group III source, NH3 is introduced as the Group V source, and metallocene magnesium (Cp2Mg) is introduced as the p-type doping source to grow the upper waveguide layer on the active region at 850°C.

[0121] The upper waveguide layer is u-GaN, which is the upper waveguide layer of the laser, wherein the growth temperature is 850°C, and the thickness of the u-GaN is 100 nm.

[0122] Comparative Example 2

[0123] A GaN-based laser epitaxial structure, which is different from that of Embodiment 1 in that the structure of the active region 105 is different.

[0124] The specific structure and growth method of the active region of Comparative Example 2 are as follows:

[0125] Under a nitrogen (N2) atmosphere, trimethylindium is introduced as the III group source and NH3 is introduced as the V group source to grow the active region on the lower waveguide layer;

[0126] The active region adopts an InGaN / GaN double quantum well structure, wherein the In x Ga 1-x The InGaN well layer is grown at a constant temperature of 750℃, the growth thickness is 3nm, the In component x=0.15, the total thickness of the GaN barrier layer in the middle barrier layer is 10nm, and the GaN barrier layer is grown at a constant temperature of 850℃.

[0127] Comparative Example 3

[0128] A gallium nitride-based laser epitaxial structure, which is different from that of Example 1 in that the structure of the active region 105 is different:

[0129] The thickness of the first InGaN well layer and the second InGaN well layer of the active region is 8nm, which is grown by a step-by-step growth method, 2nm each time, and repeated for 4 cycles to obtain the InGaN well layer.

[0130] Result detection

[0131] Optical power detection: the optical power of the laser containing the gallium nitride-based laser epitaxial structure of Examples 1-4 and Comparative Examples 1-2 under a 30mA injection current is detected by an optical power meter.

[0132] The results are shown in Table 1.

[0133] Table 1. Optical power of the gallium nitride-based laser

[0134] Optical power (mW) Example 1 35.2 Example 2 35.0 Example 3 33.0 Example 4 28.5 Example 5 35.1 Example 6 34.6 Example 7 33.6 Example 8 38.5 Example 9 36.2 Comparative Example 1 22.1 Comparative Example 2 23.1 Comparative Example 3 22.3

[0135] As can be seen from Table 1, the optical power of the laser prepared by using the epitaxial structure and the epitaxial growth method of Examples 1-9 is more than 28mW; the structure and the epitaxial growth method of the lower waveguide layer, the active region and the upper waveguide layer in Comparative Example 1 are different from those of the present application, the specific structure and the growth method of the active region in Comparative Example 2 are different from those of the present application, and the optical power of both is significantly less than that of Examples 1-9, and the optical power and the quantum efficiency are in a positive proportional relationship, which confirms that the epitaxial structure described in the present application can improve the quantum efficiency of the active region.

[0136] The laser containing the epitaxial structure of Example 1 and Comparative Example 1 is subjected to electrical injection lasing, and the results are as follows: Figure 2As shown, by comparing the light power and operating voltage curves of the two with the injected current, the light power of the laser of Example 1 is increased by 59.3% compared with the laser of Comparative Example 1, and the internal loss of the laser is greatly reduced.

[0137] Figure 3 For the light field distribution diagrams of the gallium nitride-based laser epitaxial structures of Example 1 and Comparative Example 1, it can be seen that the light field distribution curve of the laser containing the gallium nitride-based laser epitaxial structure of the present application has a narrower half-peak width, indicating that the light field confinement factor is effectively improved, and the light field confinement effect and the beam quality of the laser are better.

[0138] Obviously, the above examples of the present application are only examples for clearly illustrating the present application, and are not intended to limit the embodiments of the present application. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. Here, it is not necessary and impossible to exhaust all the embodiments. Any modification, equivalent replacement and improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the claims of the present application.

Claims

1. A gallium nitride-based laser epitaxial structure, comprising, from bottom to top, a GaN single crystal substrate (101), an n-type GaN layer (102), an n-type confinement layer (103), an n-type lower waveguide layer (104), an active region (105), an upper waveguide layer (106), an electron blocking layer (107), a p-type GaN upper waveguide layer (108), a p-type confinement layer (109), and a p-type contact layer (110), characterized in that, The active region is an asymmetric InGaN / GaN double quantum well structure, which is stacked from bottom to top as follows: a first InGaN barrier layer, a first InGaN well layer, a second GaN barrier layer, a second InGaN well layer, and a final InGaN barrier layer. The thickness of the first InGaN well layer and the second InGaN well layer in the active region is 2~6nm. The growth method is adopted, first growing 0.5~1nm at 700~800℃, then recrystallizing at 780~850℃, and repeating the growth for 3~12 cycles to obtain the InGaN well layer. The first InGaN well layer and the second InGaN well layer in the active region are In x2 Ga 1-x2 N-well layers, where 0.05 ≤ x² ≤ 0.30; The n-type lower waveguide layer (104) is n-GaN+n-In x1 Ga 1-x1 N-composite waveguide layer, where n-In x1 Ga 1-x1 N is grown using a stepwise growth method, first growing In with a thickness of 10-20 nm at 800-900℃. x1 Ga 1-x1 N, then at 850~950℃, In x1 Ga 1-x1 The N-waveguide layer is recrystallized at high temperature, and after 3 to 15 cycles of repeated growth, an In layer with a thickness of 50 to 150 nm is obtained. x1 Ga 1-x1 N-waveguide layer; where x1 < x2; The upper waveguide layer (106) is an undoped InGaN upper waveguide layer, i.e., u-In x3 Ga 1-x3 N was grown using a stepwise growth method, first growing In with a thickness of 10-20 nm at 800-900℃. x3 Ga 1-x3 N, then at 850~950℃, In x3 Ga 1-x3 The N-waveguide layer is recrystallized at high temperature, and after 3 to 15 cycles of repeated growth, an In layer with a thickness of 50 to 150 nm is obtained. x3 Ga 1-x3 N-waveguide layer; where x3 < x2; The electron blocking layer (107) is a p-type AlGaN electron blocking layer with a thickness of 5-25 nm and an Al content of 5-25%. In the stepwise growth process, the recrystallization treatment temperature is higher than the growth temperature.

2. The gallium nitride-based laser epitaxial structure as described in claim 1, characterized in that, A low-temperature GaN protective layer is inserted between the first InGaN well layer and the second GaN barrier layer in the active region, and between the second InGaN well layer and the last InGaN barrier layer.

3. The gallium nitride-based laser epitaxial structure as described in claim 1, characterized in that, The n-type confinement layer (103) is n-Al y1 Ga 1- y1 N / GaN superlattice optical confinement layer, in which n-Al y1 Ga 1- y1 The N thickness is 2~7nm, and the Al composition satisfies 0.01≤y1≤0.

2.

4. The gallium nitride-based laser epitaxial structure as described in claim 1, characterized in that, The In x1 Ga 1-x1 The In composition of the N waveguide layer satisfies 0.01≤x1≤0.

10.

5. The gallium nitride-based laser epitaxial structure as described in claim 1, characterized in that, The In x3 Ga 1-x3 The In composition of the N waveguide layer satisfies 0.01≤x3≤0.

10.

6. The gallium nitride-based laser epitaxial structure as described in claim 1, characterized in that, The p-type confinement layer (109) is p-Al y2 Ga 1-y2 N / GaN superlattice optical confinement layer, in which Al y2 Ga 1-y2 The thickness of N is 2~5nm, and 0.01≤y2≤0.

15.

7. A gallium nitride-based laser, characterized in that, The laser includes the gallium nitride-based laser epitaxial structure according to any one of claims 1 to 6.

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