Epitaxial Structure with Superlattice Inserted between Well Layer and Barrier Layer, Growth Method, and Diode

Abstract

The present invention relates to an epitaxial structure, a growth method and a diode in which a superlattice is inserted between a well layer and a barrier layer, belonging to the technical field of LED semiconductors; the epitaxial structure includes a multi-quantum well layer, and the multi-quantum well layer includes a periodic structure in which an InGaN well layer and a GaN barrier layer are alternately stacked, and a superlattice structure of BInGaN and AlInGaN is inserted between each InGaN well layer and GaN barrier layer; the growth method includes providing a sapphire substrate, and sequentially growing an AlN buffer layer, a three-dimensional nucleation layer, a two-dimensional buffer recovery layer, a u-type GaN layer, an n-type GaN layer, a stress release layer, a multi-quantum well layer and a p-type layer on the sapphire substrate; the diode includes the above epitaxial structure; to improve the luminous efficiency of the light-emitting diode.

Description

Technical Field

[0001] The present invention relates to an epitaxial structure, a growth method and a diode in which a superlattice is inserted between a well layer and a barrier layer, and belongs to the technical field of LED semiconductors. Background Art

[0002] A light-emitting diode is a semiconductor electronic component that can emit light. As an efficient, environmentally friendly and green new solid-state lighting source, it is being rapidly and widely used, such as traffic signal lights, internal and external automobile lights, urban landscape lighting, mobile phone backlights, etc. Improving the light-emitting efficiency of chips is the goal that light-emitting diodes have been constantly pursuing.

[0003] As an important component for manufacturing light-emitting diodes, in related technologies, the epitaxial wafer of a light-emitting diode usually includes a substrate and an n-type GaN layer, a multi-quantum well layer and a p-type GaN layer sequentially grown on the substrate. In related technologies, the multi-quantum well layer usually includes alternately stacked InGaN well layers and GaN barrier layers. However, there are originally large lattice mismatches and piezoelectric polarization effects between the InGaN well layer and the GaN barrier layer, resulting in more defects and leakage channels in the multi-quantum well layer, and thus the light-emitting efficiency of the finally obtained light-emitting diode epitaxial wafer is relatively low.

[0004] For example, Chinese Patent Publication No. CN107833953A discloses a method for growing a microLED multi-quantum well layer. The multi-quantum well layer includes a GaN barrier layer and an InxGa1-xN well layer, where 0 < X < 1; hydrogen is introduced during the formation of the GaN barrier layer, and hydrogen is not introduced during the formation of the InxGa1-xN well layer. By separately introducing hydrogen into the GaN barrier layer, the crystallization quality of the barrier layer can be improved, the stress between the GaN barrier layer and the InxGa1-xN well layer can be reduced, the dislocation density can be lowered, and the antistatic ability and leakage performance of the epitaxial structure can be improved. However, there are still large lattice mismatches and piezoelectric polarization effects between the well layer and the barrier layer, resulting in more defects and leakage channels in the multi-quantum well layer, and thus the problem of relatively low light-emitting efficiency of the finally obtained light-emitting diode epitaxial wafer. Summary of the Invention

[0005] The object of the present invention is to provide an epitaxial structure, a growth method and a diode in which a superlattice is inserted between a well layer and a barrier layer, so as to solve the problem that there are large lattice mismatches and piezoelectric polarization effects between the well layer and the barrier layer, resulting in more defects and leakage channels in the multi-quantum well layer, and thus the relatively low light-emitting efficiency of the finally obtained light-emitting diode epitaxial wafer.

[0006] The epitaxial structure with a superlattice inserted between the well layer and the barrier layer according to the present invention includes a multi-quantum well layer, and the multi-quantum well layer includes a periodic structure in which InGaN well layers and GaN barrier layers are alternately stacked, and a superlattice structure of BInGaN and AlInGaN is inserted between each InGaN well layer and GaN barrier layer.

[0007] A good transition can be achieved between the InGaN well layer and the GaN barrier layer through BInGaN and AlInGaN materials, which can reduce the defects generated due to lattice mismatch between the InGaN well layer and the GaN barrier layer, improve the crystal quality of the InGaN well layer and the GaN barrier layer, and ultimately improve the luminous efficiency of the light-emitting diode.

[0008] In addition, the superlattice structure of BInGaN and AlInGaN contains B atoms. The smaller B atoms can easily fill the positions of defects and dislocations in the InGaN material and the GaN material, form a stable unit cell structure and reduce the existence of defects, and reduce the probability of non-radiative recombination luminescence of carriers at the defects, thereby further improving the luminous efficiency of the light-emitting diode.

[0009] Preferably, the B component content in BInGaN of the superlattice structure of BInGaN and AlInGaN gradually increases from the side of the InGaN well layer to the side of the GaN barrier layer, and the In component content gradually decreases from the side of the InGaN well layer to the side of the GaN barrier layer.

[0010] Preferably, the Al component content in AlInGaN of the superlattice structure of BInGaN and AlInGaN gradually increases from the side of the InGaN well layer to the side of the GaN barrier layer, and the In component content gradually decreases from the side of the InGaN well layer to the side of the GaN barrier layer.

[0011] Preferably, it further includes a sapphire substrate, and an AlN buffer layer, a three-dimensional nucleation layer, a two-dimensional buffer recovery layer, a u-shaped GaN layer, an n-type GaN layer, and a stress release layer that are sequentially located on the sapphire substrate, and the multi-quantum well layer is located between the stress release layer and the p-type layer.

[0012] The growth method of the epitaxial structure with a superlattice inserted between the well layer and the barrier layer according to the present invention includes the following steps:

[0013] Step S1: Provide a sapphire substrate;

[0014] Step S2: Grow an AlN buffer layer on the sapphire substrate;

[0015] Step S3: Grow a three-dimensional nucleation layer on the AlN buffer layer;

[0016] Step S4: Grow a two-dimensional buffer recovery layer on the three-dimensional nucleation layer;

[0017] Step S5: Grow a U-shaped GaN layer on the two-dimensional buffer recovery layer;

[0018] Step S6: Grow an n-type GaN layer on the U-shaped GaN layer;

[0019] Step S7: Grow a stress release layer on the n-type GaN layer;

[0020] Step S8: Grow a multi-quantum well layer on the stress release layer. The multi-quantum well layer includes a periodic structure of alternately stacked InGaN well layers and GaN barrier layers, and a superlattice structure of BInGaN and AlInGaN is inserted between each InGaN well layer and GaN barrier layer;

[0021] Step S9: Grow a p-type layer on the multi-quantum well layer.

[0022] Preferably, the In component content in BInGaN of the superlattice structure of BInGaN and AlInGaN gradually decreases from 0.1 - 0.2 to 0, and the B component content in BInGaN gradually increases from 0 to 0.1 - 0.2; the In component content in AlInGaN of the superlattice structure of BInGaN and AlInGaN gradually decreases from 0.1 - 0.2 to 0, and the Al component content in AlInGaN gradually increases from 0 to 0.1 - 0.2.

[0023] Preferably, the number of periods of the superlattice structure of BInGaN and AlInGaN is 5 - 10, and the total thickness is 5 - 10 nm; the total thickness of a single-layer superlattice structure of BInGaN and AlInGaN is 0.5 nm - 1 nm, and the thicknesses of BInGaN and AlInGaN are the same.

[0024] Preferably, the growth temperature of BInGaN is 800°C - 850°C, and the growth pressure is 150 torr - 300 torr; the growth temperature of AlInGaN is 800°C - 900°C, and the growth pressure is 100 torr - 300 torr.

[0025] The diode of the present invention includes the epitaxial structure with a superlattice inserted between the well layer and the barrier layer as described above.

[0026] Compared with the existing technology, the advantages of an epitaxial structure, a growth method, and a diode with a superlattice inserted between the well layer and the barrier layer of the present invention are as follows:

[0027] ① By inserting a superlattice structure of BInGaN and AlInGaN between the InGaN well layer and the GaN barrier layer, where the In composition content in this structure gradually decreases from the InGaN well layer to the GaN barrier layer, it is possible to reduce the likelihood of In atoms penetrating into the barrier layer during growth, significantly retain the In element in the well layer while also improving the growth quality of the barrier layer itself.

[0028] ② A good transition between the InGaN well layer and the GaN barrier layer can be achieved through BInGaN and AlInGaN materials, which can reduce the defects caused by lattice mismatch between the InGaN well layer and the GaN barrier layer, improve the crystal quality of the InGaN well layer and the GaN barrier layer, and ultimately improve the luminous efficiency of the light-emitting diode.

[0029] ③ The superlattice structure of BInGaN and AlInGaN contains B atoms. The relatively small B atoms can easily fill the positions of defects and dislocations in the InGaN material and the GaN material, form a stable unit cell structure and reduce the existence of defects, and reduce the probability of non-radiative recombination luminescence of carriers at the defects, thereby further improving the luminous efficiency of the light-emitting diode. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 FIG. is a schematic structural diagram of an epitaxial structure with a superlattice inserted between the well layer and the barrier layer proposed by the present invention;

[0031] Figure 2 FIG. is a schematic structural diagram of a multi-quantum well layer proposed by the present invention;

[0032] Figure 3 FIG. is a schematic structural diagram of a superlattice structure of BInGaN and AlInGaN prepared by the growth method of an epitaxial structure with a superlattice inserted between the well layer and the barrier layer proposed by the present invention.

[0033] In the figure: 1, sapphire substrate; 2, AlN buffer layer; 3, three-dimensional nucleation layer; 4, two-dimensional buffer recovery layer; 5, u-shaped GaN layer; 6, n-type GaN layer; 7, stress release layer; 8, multi-quantum well layer; 9, p-type layer; 81, InGaN well layer; 82, superlattice structure of BInGaN and AlInGaN; 83, GaN barrier layer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] Hereinafter, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0035] Embodiment 1

[0036] As Figure 1As shown in the figure, this embodiment discloses an epitaxial structure with a superlattice inserted between a well layer and a barrier layer, including a sapphire substrate 1, and an AlN buffer layer 2, a three-dimensional nucleation layer 3, a two-dimensional buffer recovery layer 4, a u-type GaN layer 5, an n-type GaN layer 6, a stress release layer 7, a multi-quantum well layer 8, and a p-type layer 9 that are sequentially located on the sapphire substrate 1.

[0037] As Figure 2 shown in the figure, the multi-quantum well layer 8 includes a periodic structure in which InGaN well layers 81 and GaN barrier layers 83 are alternately stacked, and a superlattice structure 82 of BInGaN and AlInGaN is inserted between each InGaN well layer 81 and GaN barrier layer 83.

[0038] A good transition can be achieved between the InGaN well layer 81 and the GaN barrier layer 83 through BInGaN and AlInGaN materials, which can reduce the defects generated due to lattice mismatch between the InGaN well layer 81 and the GaN barrier layer 83, improve the crystal quality of the InGaN well layer 81 and the GaN barrier layer 83, and ultimately improve the light-emitting efficiency of the light-emitting diode.

[0039] In addition, the superlattice structure of BInGaN and AlInGaN contains B atoms. The relatively small B atoms can easily fill the positions of defects and dislocations in the InGaN material and the GaN material, form a stable unit cell structure and reduce the existence of defects, and reduce the probability of non-radiative recombination luminescence of carriers at the defects, thereby further improving the light-emitting efficiency of the light-emitting diode.

[0040] Specifically, the B component content in BInGaN of the superlattice structure 82 of BInGaN and AlInGaN gradually increases from the side of the InGaN well layer 81 to the side of the GaN barrier layer 83, and the In component content gradually decreases from the side of the InGaN well layer 81 to the side of the GaN barrier layer 83.

[0041] The Al component content in AlInGaN of the superlattice structure 82 of BInGaN and AlInGaN gradually increases from the side of the InGaN well layer 81 to the side of the GaN barrier layer 83, and the In component content gradually decreases from the side of the InGaN well layer 81 to the side of the GaN barrier layer 83.

[0042] By inserting a superlattice structure of BInGaN and AlInGaN between the InGaN well layer 81 and the GaN barrier layer 83, the In component content in this structure gradually decreases from the InGaN well layer 81 to the GaN barrier layer 83, which can reduce the possibility of In atoms penetrating into the barrier layer during growth, greatly retain the In element in the well layer, and at the same time improve the growth quality of the barrier layer itself.

[0043] Here, an increase in the B component and the Al component will increase the bandgap width of the AlInGaN material and the BInGaN material, thereby enhancing the confinement ability of the barrier to injected carriers, confining electrons in the quantum well, and preventing the occurrence of electron overflow. Moreover, it can achieve lattice matching and eliminate the piezoelectric polarization effect in the quantum well, reduce the band bending, increase the overlap of the electron and hole wave functions, and improve the light-emitting efficiency of the LED device.

[0044] Example 2

[0045] This embodiment discloses a method for generating an epitaxial structure with a superlattice inserted between the well layer and the barrier layer described in Example 1, including the following steps:

[0046] Step S1: Provide a sapphire substrate 1.

[0047] Step S2: Grow an AlN buffer layer 2 on the sapphire substrate 1. Among them, the AlN buffer layer 2 is used to relieve the lattice mismatch and thermal mismatch between the sapphire substrate 1 and the subsequently grown epitaxial layer, reduce crystal defects, and improve the crystal quality of the subsequent epitaxial layer. Specifically, the thickness of the AlN buffer layer 2 is 10 - 20 nm, the growth temperature is 800 °C - 900 °C, and the growth pressure is 100 - 200 Torr.

[0048] Step S3: Grow a three-dimensional nucleation layer 3 on the AlN buffer layer 2. Adjust the reaction chamber temperature to 1000 - 1080 °C, control the reaction chamber pressure at 250 - 550 torr, grow a three-dimensional nucleation layer 3 with a thickness of 400 - 600 nm, and the growth time is 10 - 30 min.

[0049] Step S4: Grow a two-dimensional buffer recovery layer 4 on the three-dimensional nucleation layer 3. Adjust the reaction chamber temperature to 1050 - 1150 °C, control the reaction chamber pressure at 100 - 500 torr, grow a two-dimensional buffer recovery layer 4 with a thickness of 500 - 800 nm, and the growth time is 20 - 40 min.

[0050] Step S5: Grow a u-shaped GaN layer 5 on the two-dimensional buffer recovery layer 4. Adjust the reaction chamber temperature to 1050 - 1200 °C, control the reaction chamber pressure at 100 - 500 torr, and grow an undoped u-shaped GaN layer 5 with a thickness of 1 - 2 μm.

[0051] Step S6: Grow an n-type GaN layer 6 on the u-shaped GaN layer 5. Adjust the reaction chamber temperature to 1050 - 1200 °C, control the reaction chamber pressure at 100 - 500 torr, and grow an n-type GaN layer 6 with a thickness of 1 - 3 μm. The n-type GaN layer 6 can be a Si-doped GaN layer, and the Si doping concentration can be 10^18 cm^-3 - 10^20 cm^-3.

[0052] Step 7: Grow a stress release layer 7 on the n-type GaN layer 6. Adjust the reaction chamber temperature to 800 - 900 °C, control the reaction chamber pressure at 100 - 500 torr, and grow a stress release layer 7 with a thickness of 50 - 70 nm.

[0053] Step S8: Grow a multi-quantum well layer 8 on the stress release layer 7. The multi-quantum well layer 8 may include 6 - 12 periods of alternating InGaN well layers 81 and GaN barrier layers 83. The thickness of the InGaN well layer 81 may be 3 - 4 nm, and the thickness of the GaN barrier layer 83 may be 9 - 20 nm. The growth temperature of the InGaN well layer 81 is 750 - 800 °C, and the growth pressure is 400 - 600 torr. The growth temperature of the GaN barrier layer 83 is 850 - 900 °C, and the growth pressure is 400 - 600 torr.

[0054] As Figure 3 shown, insert a superlattice structure 82 of BInGaN and AlInGaN between each InGaN well layer 81 and GaN barrier layer 83. The number of periods of the superlattice structure 82 of BInGaN and AlInGaN is 5 - 10, and the total thickness is 5 - 10 nm; the growth temperature of BInGaN is 800 °C - 850 °C, the growth pressure is 150 torr - 300 torr, and the single-layer thickness is 0.25 nm - 0.5 nm; the In component content in BInGaN gradually decreases from 0.1 - 0.2 to 0, and the B component content gradually increases from 0 to 0.1 - 0.2. The growth temperature of AlInGaN is 800 °C - 900 °C, the growth pressure is 100 torr - 300 torr, and the single-layer thickness is 0.25 nm - 0.5 nm; the In component content in AlInGaN gradually decreases from 0.1 - 0.2 to 0, and the Al component content gradually increases from 0 to 0.1 - 0.2.

[0055] Here, the InGaN well layer 81 and the GaN barrier layer 83 are grown according to the design of a normal LED quantum well structure. Defects are generated between the InGaN well layer 81 and the GaN barrier layer 83 due to lattice mismatch. The insertion of the superlattice structure 82 of BInGaN and AlInGaN will reduce the lattice mismatch between the InGaN well layer 81 and the GaN barrier layer 83. By using AlInGaN with a gradually increasing Al content, the effective barrier height of electrons can be increased and the effective barrier height of holes can be reduced, confining more electrons in the quantum well and effectively preventing electron leakage. Further, the introduction of the In component in the AlInGaN quantum well layer changes the microstructure of the crystal in the quantum well. The change in the In component content forms unevenly distributed low-potential regions, which can form In cluster radiative recombination centers in the quantum well, enhancing the carrier capture ability and improving the light-emitting efficiency. The small B atoms in BInGaN can easily fill the positions of defects and dislocations in the InGaN material and the GaN material, forming a stable unit cell structure and reducing the existence of defects, and reducing the probability of non-radiative recombination luminescence of carriers at the defects, thereby further improving the light-emitting efficiency of the light-emitting diode (the B component content can be gradually increased or remain unchanged. Other requirements such as temperature, pressure, and thickness are all for improving the growth quality of the grown thin film).

[0056] Step S9: Grow a p-type layer 9 on the multi-quantum well layer 8. The p-type layer 9 is a composite layer, and the p-type layer 9 includes a p-type AlGaN electron blocking layer, a p-type GaN layer, and a p-type GaN contact layer stacked in sequence. The growth temperature of the p-type AlGaN electron blocking layer is 900 - 1000 °C, and the growth pressure can be 100 - 500 torr. The growth temperature of the p-type GaN layer can be 850 - 950 °C, and the growth pressure can be 100 - 300 torr. The doping concentration of Mg in the p-type GaN layer can be 10^18 - 10^20 cm^-3. The growth temperature of the p-type GaN contact layer can be 850 - 1000 °C, and the growth pressure can be 100 - 300 torr. After the growth of the p-type layer 9 is completed, annealing treatment can be carried out in an ammonia atmosphere. The annealing temperature is 650 - 850 °C, and the annealing treatment time is 5 - 15 minutes.

[0057] Example 3

[0058] This example discloses a diode, including the epitaxial structure with a superlattice inserted between the well layer and the barrier layer described in Example 1.

[0059] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent substitutions or changes, should be covered within the protection scope of the present invention.

Claims

1. An epitaxial structure with a superlattice inserted between well layers and barrier layers, comprising a multi-quantum well layer (8), characterized in that: The multi-quantum well layer (8) comprises a periodic structure of alternately stacked InGaN well layers (81) and GaN barrier layers (83), and a superlattice structure (82) of BInGaN and AlInGaN is inserted between each InGaN well layer (81) and GaN barrier layer (83); The B component content in the BInGaN of the BInGaN and AlInGaN superlattice structure (82) gradually increases from the InGaN well layer (81) side to the GaN barrier layer (83) side, and the In component content gradually decreases from the InGaN well layer (81) side to the GaN barrier layer (83) side; The Al component content in the AlInGaN of the BInGaN and AlInGaN superlattice structure (82) gradually increases from the InGaN well layer (81) side to the GaN barrier layer (83) side, and the In component content gradually decreases from the InGaN well layer (81) side to the GaN barrier layer (83) side.

2. An epitaxial structure with a superlattice inserted between well layers and barrier layers according to any one of claim 1, characterized in that: It also comprises a sapphire substrate (1), and an AlN buffer layer (2), a three-dimensional nucleation layer (3), a two-dimensional buffer recovery layer (4), a u-type GaN layer (5), an n-type GaN layer (6), and a stress release layer (7) which are sequentially located on the sapphire substrate (1), wherein the multi-quantum well layer (8) is located between the stress release layer (7) and the p-type layer (9).

3. A method for growing an epitaxial structure with a superlattice inserted between well layers and barrier layers according to claim 2, characterized in that: The steps include: Step S1, providing a sapphire substrate (1); Step S2, growing an AlN buffer layer (2) on the sapphire substrate (1); Step S3, growing a three-dimensional nucleation layer (3) on the AlN buffer layer (2); Step S4, growing a two-dimensional buffer recovery layer (4) on the three-dimensional nucleation layer (3); Step S5, growing a u-type GaN layer (5) on the dimensional buffer recovery layer (4); Step S6, growing an n-type GaN layer (6) on the u-type GaN layer (5); Step S7, growing a stress release layer (7) on the n-type GaN layer (6); Step S8, growing a multi-quantum well layer (8) on the stress release layer (7), the multi-quantum well layer (8) comprising a periodic structure of alternately stacked InGaN well layers (81) and GaN barrier layers (83), with a superlattice structure (82) of BInGaN and AlInGaN inserted between each InGaN well layer (81) and GaN barrier layer (83); Step S9, growing a p-type layer (9) on the multi-quantum well layer (8).

4. The method for growing an epitaxial structure with a superlattice inserted between well layers and barrier layers according to claim 3, characterized in that: The In component content in the BInGaN of the BInGaN and AlInGaN superlattice structure (82) gradually decreases from 0.1-0.2 to 0, and the B component content in the BInGaN gradually increases from 0 to 0.1-0.2; the In component content in the AlInGaN of the BInGaN and AlInGaN superlattice structure (82) gradually decreases from 0.1-0.2 to 0, and the Al component content gradually increases from 0 to 0.1-0.

2.

5. The method for growing an epitaxial structure with a superlattice inserted between well layers and barrier layers according to claim 3, characterized in that: The number of periods of the BInGaN and AlInGaN superlattice structure (82) is 5 to 10, and the total thickness is 5 to 10 nm; the total thickness of the single-layer BInGaN and AlInGaN superlattice structure (82) is 0.5 nm to 1 nm, and the thickness of BInGaN and AlInGaN is the same.

6. The method for growing an epitaxial structure with a superlattice inserted between well layers and barrier layers according to claim 3, characterized in that: The growth temperature of the BInGaN is 800° C. to 850° C., and the growth pressure is 150 torr to 300 torr; the growth temperature of the AlInGaN is 800° C. to 900° C., and the growth pressure is 100 torr to 300 torr.

7. A diode, characterized in that: The invention comprises an epitaxial structure in which a superlattice is inserted between well layers and barrier layers as described in claim 1.

8. A diode, characterized in that: It comprises an epitaxial structure with a superlattice inserted between well layers and barrier layers as described in claim 2.

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