LED epitaxial structure and preparation method thereof
By introducing alternating stacked quantum wells, quantum barrier stress relief layers, and tunneling barrier layers into the LED epitaxial structure, the problems of crystal quality and uniformity in quantum dot structure growth are solved, achieving efficient carrier radiative recombination and stress relief, and simplifying the fabrication process.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- XIAMEN CHANGELIGHT CO LTD
- Filing Date
- 2023-05-12
- Publication Date
- 2026-06-30
AI Technical Summary
In existing technologies, the growth of quantum dot structures faces challenges in achieving high crystal quality and size uniformity. In particular, the fabrication of multilayer quantum dot structures with high In content and long wavelengths is difficult to achieve, posing challenges for their application in LEDs.
By employing a stress-relieving layer composed of alternating stacked quantum wells and quantum barriers, combined with a tunneling barrier layer and a quantum dot structure, and by adjusting the thickness difference and growth temperature, an LED epitaxial structure with quantum confinement Stark effect is formed, promoting radiative recombination of charge carriers in the quantum dot structure.
This improved the radiative recombination efficiency of charge carriers in quantum dot structures, reduced stress accumulation, simplified the fabrication process, and enhanced crystal quality and uniformity.
Smart Images
Figure CN116487496B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of light-emitting diodes, and more particularly to an LED epitaxial structure and its fabrication method. Background Technology
[0002] In recent years, III-V group nitrides have attracted considerable attention in the fields of electrical engineering and optics due to their excellent physical and chemical properties (direct wide bandgap, high thermal conductivity, high electron saturation velocity, strong chemical stability, etc.). Among them, quantum dot structures (QDs), with their advantages of low dislocation density, weak polarization electric field, and strong electron binding ability, are widely used in quantum dot light-emitting diodes, single-electron transistors, etc. In addition, quantum dot structures can significantly reduce the threshold current of lasers, and have immeasurable prospects in laser applications.
[0003] However, in practical applications, due to limitations in materials, structure, and processes, the large-scale application of quantum dot structures still faces many challenges. For example, how to grow quantum dots with high crystal quality and uniform size, how to alleviate the ever-accumulating stress, and how to modulate and form 3D island-like quantum dot structures through various methods, especially the growth of multilayer quantum dot structures with high In content and long wavelengths, remains a major challenge.
[0004] In view of this, the inventors have specifically designed an LED epitaxial structure and its preparation method, which leads to this invention. Summary of the Invention
[0005] The purpose of this invention is to provide an LED epitaxial structure and its preparation method, so as to form a quantum dot structure with high crystal quality and improve the radiative recombination of charge carriers in the quantum dot structure.
[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0007] An LED epitaxial structure, comprising:
[0008] A substrate and an N-type semiconductor layer, a stress relief layer, a tunneling barrier layer, a quantum dot structure, and a P-type semiconductor layer sequentially stacked on the surface of the substrate;
[0009] The stress relief layer is used to release stress and trap charge carriers, and it includes alternating stacked quantum wells and quantum barriers; and the stress relief layer has a quantum confinement Stark effect to reduce radiative recombination of charge carriers in the stress relief layer, thereby prompting charge carriers to enter the quantum dot structure through the tunneling barrier layer.
[0010] Preferably, the thickness of the tunneling barrier layer is not greater than the thickness of the quantum barrier.
[0011] Preferably, the quantum confinement Stark effect of the stress relief layer is enhanced by adjusting the thickness difference between the quantum well and the quantum barrier.
[0012] Preferably, there is an alternating first buffer layer and a second buffer layer between the substrate and the N-type semiconductor layer, and the growth temperatures of the first buffer layer and the second buffer layer are different.
[0013] Preferably, the quantum dot structure comprises an impregnation layer, a quantum dot layer, a capping layer, and a quantum barrier layer stacked sequentially.
[0014] Specifically, the LED epitaxial structure includes a gallium nitride-based LED epitaxial structure, wherein the N-type semiconductor layer is an N-type GaN layer and the P-type semiconductor layer is a P-type GaN layer.
[0015] Preferably, the stress relief layer comprises alternately stacked InGaN quantum wells and GaN quantum barriers, and the tunneling barrier layer comprises an AlInGaN tunneling barrier layer.
[0016] Preferably, the quantum dot structure comprises an InGaN wetting layer, an InGaN quantum dot layer, a GaN capping layer, and a GaN quantum barrier layer stacked sequentially.
[0017] This invention provides a method for fabricating an LED epitaxial structure, comprising:
[0018] Provide a substrate;
[0019] An N-type semiconductor layer, a stress relief layer, a tunneling barrier layer, a quantum dot structure, and a P-type semiconductor layer are sequentially grown on the surface of the substrate.
[0020] The stress relief layer is used to release stress and trap charge carriers, and it includes alternating stacked quantum wells and quantum barriers; and the stress relief layer has a quantum confinement Stark effect to reduce radiative recombination of charge carriers in the stress relief layer, thereby prompting charge carriers to enter the quantum dot structure through the tunneling barrier layer.
[0021] Preferably, the thickness of the tunneling barrier layer is not greater than the thickness of the quantum barrier.
[0022] Preferably, the quantum confinement Stark effect of the stress relief layer is enhanced by adjusting the thickness difference between the quantum well and the quantum barrier.
[0023] Specifically, when the LED epitaxial structure includes a gallium nitride-based LED epitaxial structure, the N-type semiconductor layer is an N-type GaN layer, and the P-type semiconductor layer is a P-type GaN layer, then:
[0024] The stress relief layer comprises alternately stacked InGaN quantum wells and GaN quantum barriers, and the tunneling barrier layer comprises an AlInGaN tunneling barrier layer.
[0025] The quantum dot structure comprises an InGaN wetting layer, an InGaN quantum dot layer, a GaN capping layer, and a GaN quantum barrier layer stacked sequentially.
[0026] Preferably, the transition growth of the InGaN wetting layer and the InGaN quantum dot layer is achieved by interrupting the material source supply. Further, the interruption time of the material source supply is 10s-15s, including the endpoint value.
[0027] Preferably, an InGaN quantum dot layer with a periodic structure is formed by interrupting the ammonia gas flow.
[0028] Preferably, the GaN capping layer is formed by increasing the growth temperature in stages, and hydrogen gas is introduced during the formation of the last GaN capping layer.
[0029] As can be seen from the above technical solution, the LED epitaxial structure provided by the present invention includes a substrate and an N-type semiconductor layer, a stress relief layer, a tunneling barrier layer, a quantum dot structure, and a P-type semiconductor layer sequentially stacked on the surface of the substrate; wherein, the stress relief layer is used to release stress and trap charge carriers, and includes alternating stacked quantum wells and quantum barriers; and the stress relief layer has a quantum confinement Stark effect to reduce the radiative recombination of charge carriers in the stress relief layer, and promote the charge carriers to enter the quantum dot structure through the tunneling barrier layer, thereby improving the radiative recombination of charge carriers in the quantum dot structure.
[0030] Secondly, by setting the thickness of the tunneling barrier layer to be no greater than the thickness of the quantum barrier, electron tunneling is facilitated, and the thinner tunneling barrier layer can reduce stress accumulation, laying the foundation for the subsequent growth of quantum dot structures.
[0031] Then, by adjusting the thickness difference between the quantum well and the quantum barrier, the stress relief layer can have a larger quantum well width, thereby easily and conveniently achieving an enhanced quantum confinement Stark effect in the stress relief layer.
[0032] Next, an alternating first buffer layer and a second buffer layer are formed between the substrate and the N-type semiconductor layer, with the first and second buffer layers grown at different temperatures. By alternating high and low temperatures to form the first and second buffer layers, dislocations can be effectively annihilated, reducing the lattice mismatch problem between the substrate and the subsequently grown materials.
[0033] The present invention also provides a method for preparing an LED epitaxial structure, which achieves the above-mentioned technical effects while being simple to operate and easy to implement.
[0034] Secondly, the present invention provides a method for preparing an LED epitaxial structure, which achieves the transition growth of the InGaN wetting layer and the InGaN quantum dot layer by interrupting the material source; this helps stress relaxation, thereby forming a 3D island structure, allowing atoms to relax to the position with the most suitable energy, and achieving thermodynamic dynamic equilibrium.
[0035] Furthermore, the interruption time of the material source is 10s-15s, including the endpoint value. By selecting the growth interruption time, atoms have sufficient time to migrate to the lowest energy position; and the deattachment of atoms is avoided due to the interruption time being too long.
[0036] Then, by interrupting the ammonia gas flow, an InGaN quantum dot layer with a periodic structure is formed. This causes the surface of the InGaN quantum dot layer to transition from nitrogen (N) stability to In stability, allowing the atoms to reach thermodynamic equilibrium and relax to their most energy-stable positions, further promoting the formation of 3D island-like structures.
[0037] Finally, by increasing the growth temperature in stages to form a GaN capping layer, and by introducing hydrogen gas during the formation of the last GaN capping layer, the grain boundary and dislocation defects were significantly reduced, resulting in a significant improvement in crystal quality. Attached Figure Description
[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.
[0039] Figure 1 This is a schematic diagram of the LED epitaxial structure provided in an embodiment of the present invention;
[0040] Figure 2 This is a schematic diagram of the structure of the buffer layer provided in an embodiment of the present invention;
[0041] Figure 3 This is a schematic diagram of the stress relief layer provided in an embodiment of the present invention;
[0042] Figure 4 This is a schematic diagram of the quantum dot structure provided in an embodiment of the present invention;
[0043] Figure 5 This is a schematic diagram of the growth control method of the quantum dot structure provided in an embodiment of the present invention;
[0044] Explanation of symbols in the diagram:
[0045] 1. Substrate;
[0046] 2. Buffer layer; 21. First buffer layer; 22. Second buffer layer;
[0047] 3. N-type semiconductor layer;
[0048] 4. Stress relief layer; 41. Quantum well; 42. Quantum barrier;
[0049] 5. Tunneling through the barrier layer;
[0050] 6. Quantum dot structure; 61. Wetting layer; 62. Quantum dot layer; 63. Capping layer; 64. Quantum barrier layer.
[0051] 7. Electron blocking layer;
[0052] 8. P-type semiconductor layer. Detailed Implementation
[0053] To make the content of this invention clearer, the following description, in conjunction with the accompanying drawings, further illustrates the invention. This invention is not limited to this specific embodiment. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.
[0054] Example 1
[0055] like Figure 1 As shown, an LED epitaxial structure includes:
[0056] Substrate 1 and N-type semiconductor layer 3, stress relief layer 4, tunneling barrier layer 5, quantum dot structure 6 and P-type semiconductor layer 8 are sequentially stacked on the surface of substrate 1;
[0057] The stress relief layer 4 is used to relieve stress and capture charge carriers, such as... Figure 3 As shown, it includes alternating stacked quantum wells 41 and quantum barriers 42; and the stress relief layer 4 has a quantum-confined Stark effect to reduce radiative recombination of charge carriers in the stress relief layer 4, thereby enabling charge carriers to enter the quantum dot structure 6 through the tunneling barrier layer 5.
[0058] Furthermore, the thickness of the tunneling barrier layer 5 is not greater than the thickness of the quantum barrier 42.
[0059] Furthermore, by adjusting the thickness difference between the quantum well 41 and the quantum barrier 42, the stress relief layer 4 can be made to have an enhanced quantum confinement Stark effect.
[0060] Furthermore, a buffer layer 2 is provided between the substrate 1 and the N-type semiconductor layer 3, such as... Figure 2As shown, the buffer layer 2 includes an alternately stacked first buffer layer 21 and a second buffer layer 22, and the growth temperatures of the first buffer layer 21 and the second buffer layer 22 are different.
[0061] Furthermore, such as Figure 4 As shown, the quantum dot structure 6 includes an impregnation layer 61, a quantum dot layer 62, a capping layer 63, and a quantum barrier layer 64 stacked sequentially.
[0062] Furthermore, an electron blocking layer 7 is provided between the quantum dot structure 6 and the P-type semiconductor layer 8.
[0063] This invention also provides a method for preparing an LED epitaxial structure, comprising:
[0064] Provide a substrate 1;
[0065] An N-type semiconductor layer 3, a stress relief layer 4, a tunneling barrier layer 5, a quantum dot structure 6, and a P-type semiconductor layer 8 are sequentially grown on the surface of the substrate 1.
[0066] The stress relief layer 4 is used to release stress and capture charge carriers, and includes alternating stacked quantum wells 41 and quantum barriers 42; and the stress relief layer 4 has a quantum confinement Stark effect to reduce radiative recombination of charge carriers in the stress relief layer 4, so as to promote the charge carriers to enter the quantum dot structure 6 through the tunneling barrier layer 5.
[0067] Furthermore, the thickness of the tunneling barrier layer 5 is not greater than the thickness of the quantum barrier 42.
[0068] Furthermore, by adjusting the thickness difference between the quantum well 41 and the quantum barrier 42, the quantum confinement Stark effect of the stress relief layer 4 is enhanced.
[0069] Furthermore, a buffer layer 2 is provided between the substrate 1 and the N-type semiconductor layer 3. The buffer layer 2 includes an alternately stacked first buffer layer 21 and a second buffer layer 22, and the growth temperatures of the first buffer layer 21 and the second buffer layer 22 are different.
[0070] Furthermore, the quantum dot structure 6 includes an impregnation layer 61, a quantum dot layer 62, a capping layer 63, and a quantum barrier layer 64 stacked sequentially.
[0071] As can be seen from the above technical solution, the LED epitaxial structure provided by the present invention includes a substrate 1 and an N-type semiconductor layer 3, a stress relief layer 4, a tunneling barrier layer 5, a quantum dot structure 6, and a P-type semiconductor layer 8 sequentially stacked on the surface of the substrate 1; wherein, the stress relief layer 4 is used to release stress and trap charge carriers, and includes alternating stacked quantum wells 41 and quantum barriers 42; and the stress relief layer 4 has a quantum confinement Stark effect to reduce the radiative recombination of charge carriers in the stress relief layer 4, and promote the charge carriers to enter the quantum dot structure 6 through the tunneling barrier layer 5, thereby improving the radiative recombination of charge carriers in the quantum dot structure 6.
[0072] Secondly, by setting the thickness of the tunneling barrier layer 5 to be no greater than the thickness of the quantum barrier 42, electron tunneling is facilitated, and the thinner tunneling barrier layer 5 can reduce stress accumulation, laying the foundation for the subsequent growth of the quantum dot structure 6.
[0073] Then, by adjusting the thickness difference between the quantum well 41 and the quantum barrier 42, the stress relief layer 4 can have a larger quantum well width, thereby easily and conveniently enhancing the quantum confinement Stark effect of the stress relief layer 4.
[0074] Next, a first buffer layer 21 and a second buffer layer 22 are alternately stacked between the substrate 1 and the N-type semiconductor layer 3, and the growth temperatures of the first buffer layer 21 and the second buffer layer 22 are different. By forming the first buffer layer 21 and the second buffer layer 22 at alternating high and low temperatures, dislocations can be effectively annihilated, reducing the lattice mismatch problem between the substrate 1 and the subsequently grown materials.
[0075] The present invention also provides a method for preparing an LED epitaxial structure, which achieves the above-mentioned technical effects while being simple to operate and easy to implement.
[0076] Example 2
[0077] In the embodiments of this application, when the technical solution described in Embodiment 1 is applied to a gallium nitride-based LED epitaxial structure, such as... Figures 1 to 4 As shown, the LED epitaxial structure includes:
[0078] Substrate 1 and N-type semiconductor layer 3, stress relief layer 4, tunneling barrier layer 5, quantum dot structure 6, electron blocking layer 7 and P-type semiconductor layer 8 are sequentially stacked on the surface of substrate 1.
[0079] The stress relief layer 4 is used to release stress and capture charge carriers, and includes alternating stacked quantum wells 41 and quantum barriers 42; and the stress relief layer 4 has a quantum confinement Stark effect to reduce radiative recombination of charge carriers in the stress relief layer 4, so as to promote the charge carriers to enter the quantum dot structure 6 through the tunneling barrier layer 5.
[0080] The stress relief layer 4 comprises alternately stacked InGaN quantum wells 41 and GaN quantum barriers 42.
[0081] The tunneling barrier layer 5 includes an AlInGaN tunneling barrier layer 5.
[0082] The quantum dot structure 6 includes an InGaN wetting layer 61, an InGaN quantum dot layer 62, a GaN capping layer 63, and a GaN quantum barrier layer 64 stacked sequentially.
[0083] It should be noted that the substrate 1 includes any one of sapphire, silicon carbide, silicon, gallium nitride, and aluminum nitride. The N-type semiconductor layer 3 is an N-type GaN layer, and the P-type semiconductor layer 8 is a P-type GaN layer. The P-type dopant can be, but is not limited to, Mg doping, and the N-type dopant can be, but is not limited to, Si.
[0084] Based on the above embodiments, in one embodiment of this application, the thickness of the tunneling barrier layer 5 is no greater than the thickness of the quantum barrier 42. This facilitates electron tunneling, and the thinner tunneling barrier layer 5 reduces stress accumulation, laying the foundation for the subsequent growth of the quantum dot structure 6.
[0085] Based on the above embodiments, in one embodiment of this application, by adjusting the thickness difference between the quantum well 41 and the quantum barrier 42, the stress relief layer 4 can achieve an enhanced quantum confinement Stark effect. This allows for a simple and convenient way to achieve the enhanced quantum confinement Stark effect in the stress relief layer 4.
[0086] Based on the above embodiments, in one embodiment of this application, a first buffer layer 21 and a second buffer layer 22 are alternately stacked between the substrate 1 and the N-type semiconductor layer 3, and the growth temperatures of the first buffer layer 21 and the second buffer layer 22 are different. By alternating high and low temperatures to form the first buffer layer 21 and the second buffer layer 22, dislocations can be effectively annihilated, reducing the lattice mismatch problem between the substrate 1 and the subsequently grown materials. Specifically, the first buffer layer 21 and the second buffer layer 22 can be undoped GaN buffer layers 2.
[0087] As can be seen from the above technical solution, the LED epitaxial structure provided by the present invention includes a substrate 1 and an N-type semiconductor layer 3, a stress relief layer 4, a tunneling barrier layer 5, a quantum dot structure 6, and a P-type semiconductor layer 8 sequentially stacked on the surface of the substrate 1; wherein, the stress relief layer 4 is used to release stress and trap charge carriers, and includes alternating stacked quantum wells 41 and quantum barriers 42; and the stress relief layer 4 has a quantum confinement Stark effect to reduce the radiative recombination of charge carriers in the stress relief layer 4, and promote the charge carriers to enter the quantum dot structure 6 through the tunneling barrier layer 5, thereby improving the radiative recombination of charge carriers in the quantum dot structure 6.
[0088] Secondly, by setting the thickness of the tunneling barrier layer 5 to be no greater than the thickness of the quantum barrier 42, electron tunneling is facilitated, and the thinner tunneling barrier layer 5 can reduce stress accumulation, laying the foundation for the subsequent growth of the quantum dot structure 6.
[0089] Then, by adjusting the thickness difference between the quantum well 41 and the quantum barrier 42, the stress relief layer 4 is made to have a larger quantum well width 41, thereby easily and conveniently realizing that the stress relief layer 4 has an enhanced quantum confinement Stark effect.
[0090] Next, a first buffer layer 21 and a second buffer layer 22 are alternately stacked between the substrate 1 and the N-type semiconductor layer 3, and the growth temperatures of the first buffer layer 21 and the second buffer layer 22 are different. By forming the first buffer layer 21 and the second buffer layer 22 at alternating high and low temperatures, dislocations can be effectively annihilated, reducing the lattice mismatch problem between the substrate 1 and the subsequently grown materials.
[0091] Example 3
[0092] This invention also provides a method for fabricating the LED epitaxial structure described in Example 2. The equipment used is MOCVD, with trimethyl / ethylgallium™Ga / TEGa, trimethylaluminum™Al, and ammonia NH3 as the Ga source, Al source, and nitrogen source, respectively, and N2 as the carrier gas. The N-type and P-type doping sources are silane SiH4 and magnesium pyrocene CP2Mg, respectively.
[0093] S01, Provide a substrate 1;
[0094] Substrate 1 includes any one of sapphire, silicon carbide, silicon, gallium nitride, and aluminum nitride.
[0095] S02, A buffer layer 2 and an N-type GaN layer are grown on the surface of the substrate 1; In one embodiment of the present invention, the buffer layer 2 has an alternately stacked first buffer layer 21 and a second buffer layer 22, and the growth temperatures of the first buffer layer 21 and the second buffer layer 22 are different.
[0096] Specifically, in this step, substrate 1 is placed in an MOCVD reaction chamber and hydrogenated with high-purity hydrogen gas for about 5-10 minutes at a temperature of approximately 1100°C. Then, the temperature is lowered to approximately 500-600°C, and Ga and N sources are introduced to grow a first buffer layer 21 (undoped GaN buffer layer 2) with a thickness of approximately 10-30 nm. The temperature is then raised to 1000-1100°C to grow a second buffer layer 22 with a thickness of approximately 10-30 nm, thus forming buffer layer 2. The alternating high and low temperatures used to form the first buffer layer 21 and the second buffer layer 22 effectively annihilate dislocations and reduce the lattice mismatch problem between substrate 1 and the subsequently grown materials.
[0097] Next, silane (SiH4) is introduced to grow a GaN layer with a thickness of about 2-3 μm and doped with Si, with a doping concentration of 1-5 × 10⁻⁵. 18 cm -3 Thus, an N-type semiconductor layer 3 is formed.
[0098] S03. A stress relief layer 4 is grown on the surface of the N-type GaN layer. In one embodiment of the present invention, the stress relief layer 4 includes alternately stacked InGaN quantum wells 41 and GaN quantum barriers 42. By adjusting the thickness difference between the InGaN quantum wells 41 and GaN quantum barriers 42, the stress relief layer 4 is made to have a quantum confinement Stark effect.
[0099] Specifically, in this step, the doping source silane (SiH4) is turned off, the temperature is lowered to 850-950℃, and a GaN quantum barrier 42 with a thickness of about 10-15 nm is grown; the temperature is further lowered to 750-800℃, and an In source is introduced to grow an InGaN quantum well 41 with a thickness of about 3-5 nm; finally, the above periodic structure is repeated, with a growth period of N, where N is 3 to 10; thus forming the stress relief layer 4. By adjusting the thickness difference between the InGaN quantum well 41 and the GaN quantum barrier 42, the stress relief layer 4 has a larger quantum well width 41, thereby easily and conveniently achieving an enhanced quantum confinement Stark effect in the stress relief layer 4.
[0100] S04. A tunneling barrier layer 5 is grown on the surface of the stress relief layer 4. In one embodiment of the present invention, the tunneling barrier layer 5 comprises an AlInGaN tunneling barrier layer 5. Further, the thickness of the tunneling barrier layer 5 is not greater than the thickness of the GaN quantum barrier 42.
[0101] Specifically, in this step, an Al source is introduced to grow an AlInGaN tunneling barrier layer 5 with a thickness of approximately 3-8 nm. The thickness of the AlInGaN tunneling barrier layer 5 is kept no greater than the thickness of the GaN quantum barrier 42, which facilitates electron tunneling. Furthermore, the thinner tunneling barrier layer 5 reduces stress accumulation, laying the foundation for the subsequent growth of the quantum dot structure 6.
[0102] S05. A quantum dot structure 6 is grown on the surface of the tunneling barrier layer 5. In one embodiment of the present invention, the quantum dot structure 6 includes an InGaN wetting layer 61, an InGaN quantum dot layer 62, a GaN capping layer 63, and a GaN quantum barrier layer 64 stacked sequentially. In one embodiment of the present invention, the transition growth between the InGaN wetting layer 61 and the InGaN quantum dot layer 62 is achieved by interrupting the material source. In one embodiment of the present invention, the GaN capping layer 63 is formed by increasing the growth temperature in stages, and hydrogen gas is introduced during the formation of the last stage of the GaN capping layer 63.
[0103] Specifically, such as Figure 5 As shown, in this step, the Al source is turned off, the temperature is lowered to 600-700℃, and N2 and NH3 are introduced. After the temperature stabilizes, a 3-10 nm thick InGaN wetting layer 61 is grown using TMIn / TEGa, with a growth time t0 of 15-25 s. Then, the growth is interrupted for a time t1 of 10-15 s. By selecting the growth interruption time, atoms have sufficient time to migrate to the lowest energy position, and the debonding of atoms is avoided due to excessively long interruption time.
[0104] Then, the InGaN quantum dot layer 62 is grown by alternating the introduction and interruption of NH3; specifically, the time for introducing NH3 corresponds to t2, and the time for stopping NH3 corresponds to t3, where t2 ≥ 3s and t3 ≤ 5s, and this growth is repeated for 3-10 or more cycles. By interrupting the introduction of ammonia, an InGaN quantum dot layer 62 with a periodic structure is formed; this causes the surface of the InGaN quantum dot layer to change from nitrogen (N) stability to In stability, the atoms reach thermodynamic equilibrium, and relax to their most energy-stable positions, further promoting the formation of 3D island structures.
[0105] Next, the GaN capping layer 63 is grown. The GaN capping layer 63 is formed through at least two steps (corresponding to a first GaN capping layer 63 and a second GaN capping layer 63) by increasing the growth temperature, and hydrogen gas is introduced during the formation of the second GaN capping layer 63. Specifically, the In source is turned off, and a first GaN capping layer 63 with a thickness of approximately 1-3 nm is grown to protect the quantum dots from subsequent temperature increases; then, the temperature is increased to 800-900°C, and H2 is introduced to grow a second GaN capping layer 63 with a thickness of approximately 3-5 nm. As a preferred embodiment, the temperature increase and H2 introduction can be performed in a linear manner. This significantly reduces grain boundary and dislocation defects, resulting in a marked improvement in crystal quality.
[0106] S06. A GaN quantum barrier layer 64 is grown on the surface of the quantum dot structure 6.
[0107] Specifically, in this step, a GaN quantum barrier layer 64 with a thickness of 15-25 nm is grown; and a high-quality GaN quantum barrier layer 64 is grown by continuously introducing H2.
[0108] S07. An electron blocking layer 7 is grown on the surface of the GaN quantum barrier layer 64; in one embodiment of the present invention, the electron blocking layer 7 includes a p-type AlGaN electron blocking layer 7.
[0109] Specifically, in this step, an Al source and Mg2+ (CP2Mg) are introduced to grow an AlGaN electron blocking layer 7 with a thickness of about 5-10 nm and Mg doping, with a doping concentration of 1-5 × 10⁻⁵. 18 cm -3 Thus, a P-type AlGaN electron blocking layer 7 is formed.
[0110] S08. A P-type GaN layer is fabricated on the surface of the electron blocking layer 7;
[0111] Specifically, in this step, the Al source is turned off, and the Mg doping concentration is adjusted to 1-5*10⁻⁵. 19 cm -3 A P-type GaN layer with a thickness of 10-20 nm is grown. Then, it is annealed at 850-900℃ for 20-30 minutes in an N2 atmosphere to finally form the P-type semiconductor layer 8.
[0112] The method for preparing LED epitaxial structures provided by this invention is simple to operate and easy to implement.
[0113] Secondly, the present invention provides a method for preparing an LED epitaxial structure, which achieves the transition growth of the InGaN wetting layer 61 and the InGaN quantum dot layer 62 by interrupting the material source; this helps stress relaxation, thereby forming a 3D island structure, allowing atoms to relax to the position with the most suitable energy, and achieving thermodynamic dynamic equilibrium.
[0114] Furthermore, the interruption time of the material source is 10s-15s, including the endpoint value. By selecting the growth interruption time, atoms have sufficient time to migrate to the lowest energy position; and the deattachment of atoms is avoided due to the interruption time being too long.
[0115] Then, by interrupting the ammonia gas flow, an InGaN quantum dot layer 62 with a periodic structure is formed. This causes the surface of the InGaN quantum dot layer to change from nitrogen (N) stability to In stability, allowing the atoms to reach thermodynamic equilibrium and relax to their most energy-stable positions, further promoting the formation of 3D island structures.
[0116] Finally, GaN capping layer 63 was formed by increasing the growth temperature in stages, and hydrogen gas was introduced during the formation of the last GaN capping layer 63, which significantly reduced grain boundary and dislocation defects, resulting in a significant improvement in crystal quality.
[0117] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.
[0118] It should also be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or apparatus comprising a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or apparatus that includes the aforementioned element.
[0119] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. An LED epitaxial structure, characterized in that, include: A substrate and an N-type semiconductor layer, a stress relief layer, a tunneling barrier layer, a quantum dot structure, and a P-type semiconductor layer sequentially stacked on the surface of the substrate; The stress relief layer is used to release stress and trap charge carriers, and it includes alternating stacked quantum wells and quantum barriers; and the stress relief layer has a quantum confinement Stark effect to reduce radiative recombination of charge carriers in the stress relief layer, thereby prompting charge carriers to enter the quantum dot structure through the tunneling barrier layer.
2. The LED epitaxial structure according to claim 1, characterized in that, The thickness of the tunneling barrier layer is no greater than the thickness of the quantum barrier.
3. The LED epitaxial structure according to claim 1, characterized in that, The quantum confinement Stark effect of the stress relief layer is enhanced by adjusting the thickness difference between the quantum well and the quantum barrier.
4. The LED epitaxial structure according to claim 1, characterized in that, There are alternating layers of a first buffer layer and a second buffer layer between the substrate and the N-type semiconductor layer, and the growth temperatures of the first buffer layer and the second buffer layer are different.
5. The LED epitaxial structure according to claim 1, characterized in that, The quantum dot structure comprises an impregnation layer, a quantum dot layer, a capping layer, and a quantum barrier layer stacked sequentially.
6. The LED epitaxial structure according to any one of claims 1 to 5, characterized in that, The LED epitaxial structure includes a gallium nitride-based LED epitaxial structure, wherein the N-type semiconductor layer is an N-type GaN layer and the P-type semiconductor layer is a P-type GaN layer.
7. The LED epitaxial structure according to claim 6, characterized in that, The stress relief layer comprises alternating stacked InGaN quantum wells and GaN quantum barriers, and the tunneling barrier layer comprises an AlInGaN tunneling barrier layer.
8. The LED epitaxial structure according to claim 6, characterized in that, The quantum dot structure comprises an InGaN wetting layer, an InGaN quantum dot layer, a GaN capping layer, and a GaN quantum barrier layer stacked sequentially.
9. A method for fabricating an LED epitaxial structure, characterized in that, include: Provide a substrate; An N-type semiconductor layer, a stress relief layer, a tunneling barrier layer, a quantum dot structure, and a P-type semiconductor layer are sequentially grown on the surface of the substrate. The stress relief layer is used to release stress and trap charge carriers, and it includes alternating stacked quantum wells and quantum barriers; and the stress relief layer has a quantum confinement Stark effect to reduce radiative recombination of charge carriers in the stress relief layer, thereby prompting charge carriers to enter the quantum dot structure through the tunneling barrier layer.
10. The method for preparing an LED epitaxial structure according to claim 9, characterized in that, The thickness of the tunneling barrier layer is no greater than the thickness of the quantum barrier.
11. The method for preparing an LED epitaxial structure according to claim 9, characterized in that, The quantum confinement Stark effect of the stress relief layer is enhanced by adjusting the thickness difference between the quantum well and the quantum barrier.
12. The method for preparing an LED epitaxial structure according to claim 9, characterized in that, The LED epitaxial structure includes a gallium nitride-based LED epitaxial structure, wherein the N-type semiconductor layer is an N-type GaN layer and the P-type semiconductor layer is a P-type GaN layer. Therefore: The stress relief layer comprises alternately stacked InGaN quantum wells and GaN quantum barriers, and the tunneling barrier layer comprises an AlInGaN tunneling barrier layer. The quantum dot structure comprises an InGaN wetting layer, an InGaN quantum dot layer, a GaN capping layer, and a GaN quantum barrier layer stacked sequentially.
13. The method for preparing an LED epitaxial structure according to claim 12, characterized in that, The transition growth of the InGaN wetting layer and the InGaN quantum dot layer is achieved by interrupting the material source supply.
14. The method for preparing an LED epitaxial structure according to claim 13, characterized in that, An InGaN quantum dot layer with a periodic structure is formed by interrupting the ammonia gas supply.