Stress regulation structure and growth method thereof

Abstract

The present application relates to gallium nitride homoepitaxy technical field, disclose a kind of stress regulation structure and its growth method, including epitaxial wafer, the structure of the epitaxial wafer is from bottom to top in turn substrate, first regulation layer, second regulation layer, third regulation layer, fourth regulation layer, lower limit layer, lower waveguide layer, active layer and P-type semiconductor layer.The stress regulation structure is by Si gradual change doping in first regulation layer, Si doping in second regulation layer continues Si gradual change doping on the basis of first regulation layer gradual change doping, then constant Si doping again, so that the Si uniform gradual change in the growth phase of Si gradual change doping of first regulation layer and second regulation layer, can reduce the fluctuation of stress, more evenly dispersed stress, the thickness of first regulation layer and second regulation layer is thicker, stress is better regulated, so that the time of stress relaxation is shorter, reduce dislocation continuation upwards, so as to achieve the purpose of reducing V-shaped pit of dislocation guide in homoepitaxy, improve device performance.

Description

Technical Field

[0001] This invention relates to the field of gallium nitride homoepitaxial technology, specifically to a stress-controlled structure and its growth method. Background Technology

[0002] Semiconductor lasers are a very important type of laser electronic device. Compared with other types of lasers, they have advantages such as small size, low power consumption, high efficiency, and no pollution. They have important applications in laser cutting, laser welding, laser display, laser lighting, laser communication, and laser detection. GaN-based semiconductor lasers are a typical example. By modulating the composition ratio of Al and In in AlGaN and InGaN, their emission wavelengths can cover a range from ultraviolet to green light. Currently, the industry has been optimizing and implementing the waveguide structure of lasers based on the main characteristics of invention, achieving better results and further improving the performance of GaN-based lasers.

[0003] In epitaxial GaN lasers, high-Al content AlGaN is often used to confine the light. When high-Al content AlGaN is grown on top of GaN, the AlGaN will be subjected to large tensile stress due to the difference in lattice constant and thermal expansion coefficient, which will eventually lead to cracks.

[0004] Existing technology involves inserting a low-Al content AlGaN and InGaN anti-crack layer between GaN and high-Al content AlGaN to regulate stress and prevent cracks. The low-Al AlGaN grows on GaN, with a smaller difference in lattice constant and less stress, allowing for partial stress relaxation before using InGaN as a buffer layer to further release stress.

[0005] However, there is still a stress-related problem that remains unsolved. Because there are fewer dislocations in homoepitaxial growth, changes in doping concentration can cause stress fluctuations. The resulting stress not only requires the growth of a thicker material for relaxation, but also has a long relaxation time, which can lead to dislocation-guided V-shaped pits. These V-shaped pits increase electron leakage and significantly reduce device performance. Summary of the Invention

[0006] (a) Technical problems to be solved

[0007] To address the shortcomings of existing technologies, this invention provides a stress-controlled structure and its growth method, which has advantages such as reducing dislocation-guided V-shaped pits in homoepitaxial growth and improving device performance. It solves the problem that in homoepitaxial growth, due to the scarcity of dislocations, changes in doping concentration can cause stress fluctuations, resulting in stress that not only requires the growth of thicker materials for relaxation but also has a long relaxation time, which in turn leads to dislocation-guided V-shaped pits. These V-shaped pits increase electron leakage and significantly reduce device performance.

[0008] (II) Technical Solution

[0009] A stress-controlled structure includes an epitaxial wafer, wherein the structure of the epitaxial wafer, from bottom to top, comprises a substrate, a first control layer, a second control layer, a third control layer, a fourth control layer, a lower confinement layer, a lower waveguide layer, an active layer, and a P-type semiconductor layer;

[0010] The first control layer is a Si graded-doped 3D growth layer;

[0011] The second control layer is a 2D growth layer that first undergoes Si gradient doping and then constant Si doping;

[0012] The third control layer is a low-Al composition layer with constant Si doping and gradually varying Al composition;

[0013] The fourth control layer is a Si-doped InGaN anti-crack layer;

[0014] The lower confinement layer is a Si-doped AlGaN optical confinement layer.

[0015] Furthermore, the substrate is a GaN substrate.

[0016] Furthermore, the Si doping concentration of the first control layer is increased from 0.8E18 atm / cm². 3 Gradually increased to 1.7E18 atm / cm 3 The thickness of the first control layer is 200nm-1um.

[0017] Furthermore, the Si doping concentration of the second control layer is increased from 1.7E18 atm / cm². 3 Gradually increased to 4E18 atm / cm 3 The growth of the second control layer is divided into a Si-doped gradient section and a Si-doped constant section. The thickness of the Si-doped gradient section is less than that of the Si-doped constant section. The thickness of the second control layer is 1µm-6µm.

[0018] Furthermore, the Si doping concentration of the third control layer is 2E18-5E18 atm / cm². 3 The Al composition of the third control layer starts from 0% and gradually increases to 0.5%-7% (mole fraction) as it grows, and then the composition remains unchanged and growth continues. The thickness of the third control layer is 100nm-5um.

[0019] Furthermore, the Si doping concentration of the fourth control layer is 2E18-5E18 atm / cm². 3 The In composition of the fourth control layer is 1%-10%, and the thickness of the fourth control layer is 20nm-500nm. The fourth control layer can also be an equivalent InGaN / GaN superlattice.

[0020] Furthermore, the lower confinement layer is an AlGaN optical confinement layer with a low Al content, the Al content can be 2%-10%, the Al content of the lower confinement layer is greater than the average Al content of the third control layer, the thickness of the lower confinement layer is 200nm-2um, and the lower confinement layer can also be an equivalent AlGaN / GaN superlattice.

[0021] Another technical problem to be solved by the present invention is to provide a method for growing stress-controlled structures, comprising the following steps:

[0022] 1) Clean the substrate;

[0023] 2) After substrate cleaning, a first control layer with a thickness of 200nm-1um is grown. The temperature is set at 1010℃-1050℃, the pressure at 100Torr-500Torr, and the pressure at V / III at 500-3000. The Si doping concentration is from 0.8E18atm / cm³. 3 Gradually increased to 1.7E18 atm / cm 3 ;

[0024] 3) After the first control layer is grown, a second control layer with a thickness of 1µm-6µm is grown. The temperature is set at 1010℃-1050℃, the pressure at 100Torr-500Torr, the pressure at V / Ⅲ at 500-3000, and the Si doping at 1.7E18atm / cm². 3 Gradually increased to 4E18 atm / cm 3 The growth process involves a Si-doped gradient section followed by a Si-doped constant section where the Si doping remains constant.

[0025] 4) After the second control layer is grown, a third control layer with a thickness of 100nm-5um is grown. The temperature is set at 1000℃-1050℃, the pressure at 100Torr-500Torr, V / Ⅲ at 500-5000, and the Si doping at 2E18-5E18 atm / cm. 3 The Al content was initially 0% and gradually increased to 0.5%-7% with growth, and then the composition was kept constant.

[0026] 5) After the third control layer is grown, a fourth control layer with a thickness of 20nm-500nm is grown. The temperature is set at 700℃-900℃, the pressure at 100Torr-600Torr, the V / Ⅲ pressure at 10000-50000, and the Si doping at 2E18-5E18 atm / cm². 3 The In component is 1%-10%;

[0027] 6) After the fourth control layer is grown, a lower confinement layer with a thickness of 200nm-2um is grown. The temperature is set at 1000℃-1050℃, the pressure at 100Torr-500Torr, V / III at 500-5000, and the Si doping at 2E18-5E18 atm / cm². 3 The Al component is 2%-10%;

[0028] 7) After the lower confinement layer is grown, the lower waveguide layer, active layer and P-type semiconductor layer are grown sequentially;

[0029] 8) After growth, cool to 600-800℃ and anneal in a pure nitrogen atmosphere for 1-10 minutes, then continue to cool to room temperature.

[0030] Furthermore, the V / III ratio of the first regulatory layer is smaller than the V / III ratio of the second regulatory layer.

[0031] Furthermore, the third control layer is grown in two stages: the first stage is growth with gradual Al doping, and the second stage is growth with constant Al doping. The thickness of the second stage is greater than that of the first stage.

[0032] Other processes after epitaxial wafer growth and annealing, such as electrode formation, exposure and etching, protective film formation, and cleavage, are well known to those skilled in the art and will not be elaborated upon in this article.

[0033] (III) Beneficial Effects

[0034] Compared with the prior art, the present invention provides a stress-controlled structure and its growth method, which has the following beneficial effects:

[0035] 1. The stress-controlled structure and its growth method involve setting a first control layer and a second control layer on a substrate. The first control layer is subjected to graded Si doping, and the second control layer is subjected to further graded Si doping based on the graded doping in the first control layer, followed by constant Si doping. This results in a uniform graded Si doping during the growth stages of the first and second control layers, which reduces stress fluctuations and distributes stress more evenly. Furthermore, the relatively thick first and second control layers allow for better stress control, resulting in shorter stress relaxation times and reduced upward dislocation propagation. This ultimately reduces dislocation-guided V-shaped pits in homoepitaxial growth, thereby improving device performance.

[0036] 2. This stress-controlled structure and its growth method maintain a constant Si doping concentration in the third and fourth control layers during growth. This preserves the stress control function of the third and fourth control layers to prevent cracking, while also preventing large stress fluctuations caused by changes in Si doping. The second control layer, a 2D growth layer, fills the lateral gaps in the vertical 3D growth layer of the first control layer, resulting in a smoother surface and providing favorable conditions for subsequent growth. The third control layer, a low-Al content layer with a gradual Al composition change, can relax some of the stress. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of a stress regulation structure according to the present invention;

[0038] Figure 2 This is a schematic diagram of the growth process of a stress-controlled structure according to the present invention;

[0039] Figure 3 This is a schematic diagram of a transmission electron microscope (TEM) of the interior of a sample according to an embodiment of the present invention;

[0040] Figure 4 This is a schematic diagram of the internal transmission electron microscope (TEM) of the comparative sample of the present invention.

[0041] In the figure: 1 Substrate, 2 First control layer, 3 Second control layer, 4 Third control layer, 5 Fourth control layer, 6 Lower confinement layer, 7 Lower waveguide layer, 8 Active layer, 9 P-type semiconductor layer, 100 Epitaxial wafer. Detailed Implementation

[0042] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] Please see Figure 1 A stress-controlled structure includes an epitaxial wafer 100, the structure of which, from bottom to top, consists of a substrate 1, a first control layer 2, a second control layer 3, a third control layer 4, a fourth control layer 5, a lower confinement layer 6, a lower waveguide layer 7, an active layer 8, and a P-type semiconductor layer 9.

[0044] The first control layer 2 is a Si graded-doped 3D growth layer;

[0045] The second control layer 3 is a 2D growth layer that first undergoes Si gradient doping and then constant Si doping.

[0046] The third control layer 4 is a low Al composition layer with constant Si doping and gradually varying Al composition;

[0047] The fourth control layer 5 is an InGaN anti-cracking layer with constant Si doping;

[0048] The lower confinement layer 6 is an AlGaN optical confinement layer with constant Si doping.

[0049] Among them, the 3D growth layer refers to the GaN layer with a vertical growth rate greater than the horizontal growth rate, and the 2D growth layer refers to the GaN layer with a horizontal growth rate greater than the vertical growth rate.

[0050] In this embodiment, substrate 1 is a GaN substrate.

[0051] In this embodiment, the Si doping concentration of the first control layer 2 is 0.8E18 atm / cm². 3 Gradually increased to 1.7E18 atm / cm 3 The thickness of the first control layer 2 is 500nm.

[0052] In this embodiment, the Si doping concentration of the second control layer 3 is 1.7E18 atm / cm³. 3 Gradually increased to 4E18 atm / cm 3 The growth of the second control layer 3 remains unchanged. It is divided into a Si-doped gradient section and a Si-doped constant section. The thickness of the Si-doped gradient section is 1.5 μm, and the thickness of the Si-doped constant section is 3.5 μm. The total thickness of the second control layer 3 is 5 μm.

[0053] In this embodiment, the Si doping concentration of the third control layer 4 is 3.5E18 atm / cm². 3 The Al content of the third control layer 4 starts from 0% and gradually increases to 2% as it grows. Then, the content remains unchanged and growth continues. The thickness of the third control layer 4 is 2 μm.

[0054] In this embodiment, the Si doping concentration of the fourth control layer 5 is 3.5E18 atm / cm². 3 The In composition of the fourth regulatory layer 5 is 6%, and the thickness of the fourth regulatory layer 5 is 200 nm.

[0055] In this embodiment, the lower confinement layer 6 is an AlGaN light confinement layer with a low Al content, the Al content can be 7%, and the thickness of the lower confinement layer 6 is 1 μm.

[0056] Another technical problem to be solved by the present invention is to provide a method for growing stress-controlled structures, such as... Figure 2 As shown, it includes the following steps:

[0057] 1) Clean substrate 1;

[0058] 2) After cleaning substrate 1, a first control layer 2 with a thickness of 500 nm is grown. The temperature is set at 1020℃, the pressure at 350 Torr, the V / III ratio at 800, and the Si doping concentration is set from 0.8E18 atm / cm³. 3 Gradually increased to 1.7E18 atm / cm 3 ;

[0059] 3) After the first control layer 2 is grown, a second control layer 3 with a thickness of 5 μm is grown. The set temperature is 1020℃, the pressure is 350 Torr, the V / III ratio is 1300, and the Si doping is 1.7E18 atm / cm². 3 Gradually increased to 4E18 atm / cm 3 A Si-doped gradient section with a thickness of 1.5 μm was grown, followed by a Si-doped constant section with a thickness of 3.5 μm with the Si doping remaining unchanged.

[0060] 4) After the growth of the second control layer 3, a third control layer 4 with a thickness of 2 μm is grown. The set temperature is 1020℃, the pressure is 350 Torr, the V / III ratio is 2000, and the Si doping is 3.5E18 atm / cm. 3 The Al content starts from 0% and gradually increases to 2% during growth. The thickness of the initial growth stage is 0.5 μm. Then, the composition remains unchanged and the thickness of the final growth stage is 1.5 μm.

[0061] 5) After the growth of the third control layer 4, a fourth control layer 5 with a thickness of 200 nm is grown. The set temperature is 850℃, the pressure is 350 Torr, the V / III ratio is 30000, and the Si doping is 3.5E18 atm / cm². 3 The In component is 7%;

[0062] 6) After the fourth control layer 5 is grown, a lower confinement layer 6 with a thickness of 1 μm is grown. The set temperature is 1020℃, the pressure is 350 Torr, V / III is 3500, and the Si doping is 3.5E18 atm / cm. 3 The Al component is 8%;

[0063] 7) After the lower confinement layer 6 is grown, the lower waveguide layer 7, the active layer 8, and the P-type semiconductor layer 9 are grown sequentially.

[0064] 8) After growth, cool down to 700℃, anneal in a pure nitrogen atmosphere for 7 minutes, and then continue to cool down to room temperature.

[0065] In this embodiment, the V / III ratio of the first control layer 2 is smaller than that of the second control layer 3.

[0066] In this embodiment, the third control layer 4 is grown in two stages. The first stage is growth with gradual Al doping, and the second stage is growth with constant Al doping. The thickness of the second stage is greater than that of the first stage.

[0067] Other processes after epitaxial wafer growth and annealing, such as electrode formation, exposure and etching, protective film formation, and cleavage, are well known to those skilled in the art and will not be elaborated upon in this article.

[0068] The transmission electron microscope (TEM) image of the interior of the sample prepared in the example is shown below. Figure 3 As shown.

[0069] The beneficial effects of this invention are:

[0070] This stress-controlled structure and its growth method involve setting a first control layer 2 and a second control layer 3 on a substrate 1. The first control layer 2 is doped with Si in a gradient manner, and the second control layer 3 is doped with Si in a gradient manner based on the gradient doping of the first control layer 2, followed by constant Si doping. This results in a uniform gradient of Si during the growth stages of the first control layer 2 and the second control layer 3, which can reduce stress fluctuations and distribute stress more evenly. At the same time, the relatively thick first control layer 2 and the second control layer 3 allow for better stress control, resulting in a shorter stress relaxation time and reducing the upward propagation of dislocations. This achieves the goal of reducing dislocation-guided V-shaped pits in homoepitaxial growth and improving device performance.

[0071] A comparative example was prepared, identical to the example except for the omission of the first control layer 2 and the second control layer 3. The resulting sample's internal transmission electron microscope (TEM) image is shown below. Figure 4 As shown.

[0072] The transmission electron microscope (TEM) images of the sample interior obtained by comparing this embodiment are shown below. Figure 3 As shown, the internal transmission electron microscope (TEM) images of the samples prepared in comparison are as follows: Figure 4 As shown, the dislocation-guided V-shaped pits in the image disappear, thus demonstrating that the embodiments employing the technical solution of the present invention have significant beneficial effects.

[0073] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A stress-regulating structure, comprising an epitaxial wafer (100), characterized in that: The structure of the epitaxial wafer (100) from bottom to top consists of a substrate (1), a first control layer (2), a second control layer (3), a third control layer (4), a fourth control layer (5), a lower confinement layer (6), a lower waveguide layer (7), an active layer (8), and a P-type semiconductor layer (9). The first control layer (2) is a Si gradient doped 3D growth layer; The second control layer (3) is a 2D growth layer with first Si gradient doping and then Si constant doping; The third control layer (4) is a low Al composition layer with constant Si doping and gradually varying Al composition; The fourth control layer (5) is a Si-doped InGaN anti-crack layer; The lower confinement layer (6) is a Si-doped AlGaN optical confinement layer; The substrate (1) is a GaN substrate; The Si doping concentration of the first control layer (2) is 0.8E18 atm / cm. 3 Gradually increased to 1.7E18 atm / cm 3 ; The Si doping concentration of the second control layer (3) is 1.7E18 atm / cm. 3 Gradually increased to 4E18 atm / cm 3 It remains unchanged afterward; The 3D growth layer refers to a GaN layer with a vertical growth rate greater than a horizontal growth rate, and the 2D growth layer refers to a GaN layer with a horizontal growth rate greater than a vertical growth rate. The Al component of the third regulatory layer (4) starts from 0% and gradually increases to 0.5%-7% as it grows, and then the component remains unchanged and the growth continues.

2. The stress regulation structure according to claim 1, characterized in that: The thickness of the first control layer (2) is 200nm-1um.

3. The stress regulation structure according to claim 1, characterized in that: The growth of the second control layer (3) is divided into a Si-doped gradient section and a Si-doped constant section. The thickness of the Si-doped gradient section is less than that of the Si-doped constant section. The thickness of the second control layer (3) is 1um-6um.

4. The stress regulation structure according to claim 1, characterized in that: The Si doping concentration of the third control layer (4) is 2E18-5E18 atm / cm. 3 The thickness of the third control layer (4) is 100nm-5um.

5. The stress regulation structure according to claim 1, characterized in that: The Si doping concentration of the fourth control layer (5) is 2E18-5E18 atm / cm. 3 The fourth control layer (5) has an In composition of 1%-10%, a thickness of 20nm-500nm, and is InGaN or an equivalent InGaN / GaN superlattice.

6. The stress regulation structure according to claim 1, characterized in that: The lower confinement layer (6) is an AlGaN optical confinement layer with a low Al content of 2%-10%. The Al content of the lower confinement layer (6) is greater than the average Al content of the third control layer (4). The thickness of the lower confinement layer (6) is 200nm-2um. The lower confinement layer (6) is AlGaN or an equivalent AlGaN / GaN superlattice.

7. A method for growing a stress-controlled structure as described in any one of claims 1-6, characterized in that, Includes the following steps: 1) Clean the substrate (1); 2) After cleaning the substrate (1), a first control layer (2) with a thickness of 200nm-1um is grown. The temperature is set to 1010℃-1050℃, the pressure is 100Torr-500Torr, V / III is 500-3000, and the Si doping concentration is 0.8E18atm / cm. 3 Gradually increased to 1.7E18 atm / cm 3 ; 3) After the first control layer (2) is grown, a second control layer (3) with a thickness of 1um-6um is grown. The temperature is set to 1010℃-1050℃, the pressure is 100Torr-500Torr, V / Ⅲ is 500-3000, and Si doping is 1.7E18atm / cm. 3 Gradually increased to 4E18 atm / cm 3 The growth process involves a Si-doped gradient section followed by a Si-doped constant section where the Si doping remains constant. 4) After the growth of the second control layer (3), a third control layer (4) with a thickness of 100nm-5um is grown. The temperature is set to 1000℃-1050℃, the pressure is 100Torr-500Torr, V / Ⅲ is 500-5000, and Si doping is 2E18-5E18atm / cm. 3 The Al content was initially 0% and gradually increased to 0.5%-7% during growth, and then the composition was kept constant. 5) After the growth of the third control layer (4), a fourth control layer (5) with a thickness of 20nm-500nm is grown. The temperature is set to 700℃-900℃, the pressure is 100Torr-600Torr, V / Ⅲ is 10000-50000, and Si doping is 2E18-5E18atm / cm. 3 The In component is 1%-10%; 6) After the fourth control layer (5) is grown, a lower confinement layer (6) with a thickness of 200nm-2um is grown. The temperature is set to 1000℃-1050℃, the pressure is 100Torr-500Torr, V / Ⅲ is 500-5000, and Si doping is 2E18-5E18atm / cm. 3 The Al component is 2%-10%; 7) After the lower confinement layer (6) is grown, the lower waveguide layer (7), the active layer (8) and the P-type semiconductor layer (9) are grown in sequence. 8) After growth, cool to 600-800℃ and anneal in a pure nitrogen atmosphere for 1-10 minutes, then continue to cool to room temperature.

8. The method for growing a stress-controlled structure according to claim 7, characterized in that: The growth of V / III in the first regulatory layer (2) is smaller than that in the second regulatory layer (3).

9. The method for growing a stress-controlled structure according to claim 7, characterized in that: The third control layer (4) is grown in two stages. The first stage is growth with gradual doping of Al composition, and the second stage is growth with constant doping of Al composition. The thickness of the second stage is greater than that of the first stage.

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