Epitaxial wafer of light-emitting diode and preparation method thereof

Abstract

The present invention relates to the technical field of semiconductor materials and discloses an epitaxial wafer for a light-emitting diode and a method for preparing the same. The epitaxial wafer comprises a substrate, a buffer layer, an undoped GaN layer, an N-type GaN layer, a multi-quantum well layer, a low-temperature P-type layer, an electron blocking layer, and a P-type GaN layer sequentially stacked on the substrate; the multi-quantum well layer has a V-shaped pit structure; and the low-temperature P-type layer comprises an AlN layer, a Mg-AlInGaN layer, and a Mg-InGaN / AlGaN superlattice structure layer sequentially stacked from bottom to top. The implementation of the present invention can increase the activated Mg concentration, increase the hole concentration, improve the hole injection efficiency, reduce the electron overflow effect, reduce the leakage current of the light-emitting diode, and improve the luminous efficiency and brightness of the light-emitting diode.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor materials, and in particular to an epitaxial wafer of a light emitting diode and a preparation method thereof. Background Art

[0002] Gallium nitride (GaN), a representative of wide-bandgap semiconductors, has for many years garnered significant attention and interest in semiconductor research worldwide. This is due to the material's inherent properties: a direct bandgap, a wide bandgap, excellent corrosion resistance, and a stable structure. Among related devices, GaN light-emitting diodes (LEDs) have achieved tremendous success, playing a vital role in lighting, display, and other fields.

[0003] There is a large lattice and thermal mismatch between sapphire and GaN. The large lattice mismatch leads to a high dislocation density in GaN thin films grown on sapphire substrates. This high dislocation density produces a large number of V-shaped pits, and dislocations are often present at the bottom of the V-pits, leading to leakage. Secondly, the energy level of the Mg acceptor is deep, approximately 170 meV. The ionization rate of Mg at room temperature is only about 1%, and the activated Mg concentration is low. Finally, the current creates a congestion effect in the LED, resulting in uneven current distribution and non-radiative recombination. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an epitaxial wafer of a light-emitting diode and a preparation method thereof, which can increase the activated Mg concentration, increase the hole concentration, improve the hole injection efficiency, reduce the electron overflow effect, reduce the leakage of the light-emitting diode, and improve the luminous efficiency and luminous brightness of the light-emitting diode.

[0005] In order to solve the above technical problems, the present invention provides, in a first aspect, an epitaxial wafer for a light-emitting diode, comprising a substrate, a buffer layer, an undoped GaN layer, an N-type GaN layer, a multi-quantum well layer, a low-temperature P-type layer, an electron blocking layer, and a P-type GaN layer stacked in sequence on the substrate; the multi-quantum well layer having a V-shaped pit structure;

[0006] The low-temperature P-type layer includes an AlN layer, a Mg-AlInGaN layer and a Mg-InGaN / AlGaN superlattice structure layer stacked in sequence from bottom to top.

[0007] As an improvement of the above solution, the Mg-InGaN / AlGaN superlattice structure layer is a Mg-InGaN layer and an AlGaN layer that are grown alternately periodically, with the number of alternating periods being 1 to 20.

[0008] As an improvement of the above solution, the doping concentration of Mg in the Mg-AlInGaN layer is lower than the doping concentration of Mg in the Mg-InGaN layer.

[0009] As an improvement to the above solution, the Mg doping concentration in the Mg-AlInGaN layer is 1×10 18 ~1×10 19 atoms / cm 3 .

[0010] As an improvement to the above solution, the Mg doping concentration in the Mg-InGaN layer is 1×10 19 ~1×10 21 atoms / cm 3 .

[0011] As an improvement to the above solution, the thickness of the AlN layer is 1 to 10 nm.

[0012] As an improvement of the above solution, the thickness of the Mg-AlInGaN layer is 1-10 nm, the Al composition is 0.01-0.1, and the In composition is 0.01-0.1.

[0013] As an improvement to the above solution, the thickness of the Mg-InGaN layer is 0.5 to 5 nm, and the In composition is 0.01 to 0.1;

[0014] The thickness of the AlGaN layer is 1-10 nm, and the Al composition is 0.01-0.1.

[0015] As an improvement of the above solution, the growth temperature of the AlN layer is 800°C to 900°C, the pressure is 50 torr to 500 torr, the growth atmosphere is N2 and NH3, and the flow ratio of N2 to NH3 is 1:(0.5 to 5);

[0016] The growth temperature of the Mg-AlInGaN layer is 800° C. to 900° C., the pressure is 50 torr to 500 torr, the growth atmosphere is N2 and NH3, and the flow ratio of N2 to NH3 is 1:(0.5 to 5);

[0017] The growth temperature of the Mg-InGaN is 800° C. to 900° C., the pressure is 50 torr to 500 torr, the growth atmosphere is N2, NH3 and H2, and the flow ratio of N2, NH3 and H2 is 1:(1-5):(1-10);

[0018] The AlGaN layer is grown at a temperature of 800° C. to 900° C., a pressure of 50 torr to 500 torr, a growth atmosphere of N2 and NH3, and a flow ratio of N2 to NH3 of 1:(0.5 to 5).

[0019] The second aspect of the present invention further provides a method for preparing the epitaxial wafer of the light-emitting diode, comprising:

[0020] Providing a sapphire substrate;

[0021] depositing a buffer layer on the substrate;

[0022] depositing an undoped GaN layer on the buffer layer;

[0023] depositing an N-type GaN layer on the undoped GaN layer;

[0024] depositing a multi-quantum well layer on the N-type GaN layer;

[0025] depositing a low-temperature P-type layer on the multi-quantum well layer;

[0026] depositing an electron blocking layer on the low-temperature P-type layer;

[0027] Depositing a P-type GaN layer on the electron blocking layer;

[0028] The low-temperature P-type layer includes an AlN layer, a Mg-AlInGaN layer and a Mg-InGaN / AlGaN superlattice structure layer stacked sequentially from bottom to top, and the Mg-InGaN / AlGaN superlattice structure layer is a periodically alternating growth of Mg-InGaN layers and AlGaN layers.

[0029] The implementation of the present invention has the following beneficial effects:

[0030] In the present invention, a low-temperature P-type layer is provided between the multi-quantum well layer and the electron blocking layer. The low-temperature P-type layer includes an AlN layer, a Mg-AlInGaN layer, and a Mg-InGaN / AlGaN superlattice structure layer stacked sequentially from bottom to top. The AlN layer, the Mg-AlInGaN layer, and the Mg-InGaN / AlGaN superlattice structure layer cooperate with each other to reduce dislocations between the bottom of the V-shaped pit and the P-type layer, thereby improving the crystal quality of the P-type layer. On the other hand, the hole expansion efficiency is improved while increasing the activation rate of Mg, thereby increasing the hole injection efficiency and improving the recombination efficiency of electrons and holes in the multi-quantum well layer, thereby improving the luminous efficiency of the LED. In addition, the low-temperature P-type layer is used to fill the V-shaped pits in the multi-quantum well layer, resulting in a smoother epitaxial layer plane, further reducing electron overflow, reducing light-emitting diode leakage, and increasing the luminous brightness of the LED chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 : A schematic structural diagram of an epitaxial wafer of a light emitting diode in the present invention;

[0032] Figure 2: Schematic diagram of the structure of the Mg-InGaN / AlGaN superlattice structure layer in the present invention;

[0033] Figure 3 : A flow chart of the preparation of an epitaxial wafer of a light emitting diode in the present invention.

[0034] Reference numerals:

[0035] 100-substrate; 200-buffer layer; 300-undoped GaN layer; 400-N-type GaN layer; 500-multi-quantum well layer; 600-low-temperature P-type layer; 610-AlN layer; 620-Mg-AlInGaN layer; 630-Mg-InGaN / AlGaN superlattice structure layer; 631-Mg-InGaN layer; 632-AlGaN layer; 700-electron blocking layer; 800-P-type GaN layer. DETAILED DESCRIPTION

[0036] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail with reference to specific embodiments below.

[0037] To solve the above problems, the first aspect of the present invention provides an epitaxial wafer for a light-emitting diode, comprising a substrate 100, a buffer layer 200, an undoped GaN layer 300, an N-type GaN layer 400, a multi-quantum well layer 500, a low-temperature P-type layer 600, an electron blocking layer 700, and a P-type GaN layer 800 sequentially stacked on the substrate 100; the multi-quantum well layer 500 has a V-shaped pit structure;

[0038] The low-temperature P-type layer 600 includes an AlN layer 610 , a Mg—AlInGaN layer 620 , and a Mg—InGaN / AlGaN superlattice structure layer 630 stacked sequentially from bottom to top.

[0039] In the present invention, a low-temperature P-type layer 600 is provided between the multi-quantum well layer 500 and the electron blocking layer 700. The low-temperature P-type layer 600 comprises an AlN layer 610, a Mg-AlInGaN layer 620, and a Mg-InGaN / AlGaN superlattice structure layer 630 stacked sequentially from bottom to top. The AlN layer 610, the Mg-AlInGaN layer 620, and the Mg-InGaN / AlGaN superlattice structure layer 630 cooperate with each other to reduce dislocations between the bottom of the V-shaped pit and the P-type layer, thereby improving the crystal quality of the P-type layer. Furthermore, the low-temperature P-type layer 600 improves the hole expansion efficiency and the activation rate of Mg, thereby improving the hole injection efficiency and the recombination efficiency of electrons and holes in the multi-quantum well layer 500, thereby enhancing the luminous efficiency of the LED. Furthermore, the low-temperature P-type layer 600 fills the V-shaped pits in the multi-quantum well layer 500, resulting in a smoother epitaxial layer plane, further reducing electron overflow and increasing the brightness of the LED chip.

[0040] Preferably, the thickness of the AlN layer 610 is 1 nm to 10 nm. When a GaN layer is deposited on a foreign substrate 100, dislocations are generated due to lattice mismatch, forming V-shaped pits. Therefore, depositing the AlN layer 610 can reduce the extension of screw dislocations at the bottom of the V-shaped pits toward the P-type GaN layer 800, thereby improving the crystal quality of the P-type GaN layer 800, reducing leakage current in the light-emitting diode, and acting as a leakage shield, thereby improving aging resistance. The thickness of the AlN layer 610 can be 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, or 10 nm, but is not limited thereto.

[0041] Preferably, the Mg-AlInGaN layer 620 has a thickness of 1 nm to 10 nm, an Al composition of 0.01 to 0.1, and an In composition of 0.01 to 0.1. Deposition of the Mg-AlInGaN layer 620 uniformly distributes holes on the surface, reduces current congestion, improves hole expansion efficiency, plays a hole expansion role, reduces defect-trapped holes, and reduces non-radiative recombination. Exemplary thicknesses of the Mg-AlInGaN layer 620 are 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, and 10 nm, but are not limited thereto.

[0042] Preferably, the Mg-InGaN / AlGaN superlattice structure layer 630 comprises a periodically alternating Mg-InGaN layer 631 and an AlGaN layer 632. The Mg-InGaN layer 631 has a thickness of 0.5 nm to 5 nm and an In composition of 0.01 to 0.1; the AlGaN layer 632 has a thickness of 1 nm to 10 nm and an Al composition of 0.01 to 0.1, with the number of overlapping periods ranging from 1 to 20. The Mg doping in the Mg-InGaN layer 631 provides sufficient holes for the light-emitting diode to emit light. Furthermore, a small amount of In can effectively reduce the Mg acceptor energy level, increase the Mg activation rate, and increase the hole concentration, thereby compensating for the low ionization rate of Mg at room temperature. The AlGaN layer 632 fills the V-shaped pits, resulting in a smoother epitaxial layer plane, reducing LED leakage and electron overflow. Finally, through periodic structural growth, the Mg memory effect is utilized to reduce the ineffective Mg concentration and reduce light absorption in the P-type layer. In the present invention, exemplary alternating period numbers are 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, and 20, but are not limited thereto; the thickness of the Mg-InGaN layer 631 is exemplarily 0.5 nm, 1 nm, 1.5 nm, 2 nm, 2.5 nm, 3 nm, 3.5 nm, 4 nm, 4.5 nm, and 5 nm, but are not limited thereto; the thickness of the AlGaN layer 632 is exemplarily 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, and 10 nm, but are not limited thereto.

[0043] Furthermore, the Mg doping concentration in the Mg-AlInGaN layer 620 is lower than the Mg doping concentration in the Mg-InGaN layer 631. By optimizing the Mg doping concentration, the resistance of the hole expansion layer can be reduced, which is beneficial for the holes in the Mg-InGaN layer 631 to be transferred to the multi-quantum well layer 500, thereby playing a better hole compensation role, thereby improving the hole injection efficiency and improving the luminous efficiency and luminous intensity of the LED chip.

[0044] Furthermore, the Mg doping concentration in the Mg-AlInGaN layer 620 is 1×10 18 atoms / cm 3 ~1×10 19 atoms / cm 3 The Mg doping concentration in the Mg-InGaN layer 631 is 1×10 19 atoms / cm 3 ~1×10 21 atoms / cm 3 The Mg doping concentration in the Mg-AlInGaN layer 620 is exemplarily 1×10 18 atoms / cm3 , 3×10 18 atoms / cm 3 , 5×10 18 atoms / cm 3 , 7×10 18 atoms / cm 3 , 9×10 18 atoms / cm 3 , 1×10 19 atoms / cm 3 , but not limited thereto; the Mg doping concentration in the Mg-InGaN layer 631 is exemplarily 1×10 19 atoms / cm 3 , 3×10 19 atoms / cm 3 , 5×10 19 atoms / cm 3 , 7×10 19 atoms / cm 3 , 9×10 19 atoms / cm 3 , 1×10 20 atoms / cm 3 , 3×10 20 atoms / cm 3 , 5×10 20 atoms / cm 3 , 7×10 20 atoms / cm 3 , 9×10 20 atoms / cm 3 , 1×10 21 atoms / cm 3 , but not limited to this.

[0045] Accordingly, the present invention also provides a method for preparing an epitaxial wafer of a light emitting diode, comprising:

[0046] S01, providing a substrate 100;

[0047] Preferably, the substrate 100 can be selected from a sapphire substrate, a SiO2 sapphire composite substrate, a silicon substrate, a silicon carbide substrate, a gallium nitride substrate, or a zinc oxide substrate. More preferably, the substrate 100 is a sapphire substrate. Sapphire is currently the most commonly used GaN-based LED substrate material. Sapphire substrates have mature preparation processes, are relatively low in price, are easy to clean and handle, and have excellent stability at high temperatures.

[0048] S02, depositing a buffer layer 200 on the substrate 100

[0049] Preferably, the buffer layer 200 is an AlN buffer layer having a thickness of 10 nm to 50 nm. The AlN buffer layer provides nucleation centers with the same orientation as the substrate 100, relieves stress generated by the lattice mismatch between GaN and the substrate 100, and relieves thermal stress generated by the mismatch in thermal expansion coefficients. It provides a flat nucleation surface for further growth, reduces the contact angle of nucleation growth, and enables island-like GaN grains to connect into a surface within a smaller thickness, thus transforming to two-dimensional epitaxial growth.

[0050] Furthermore, after the buffer layer is deposited, it is pretreated. The pretreatment includes: transferring the sapphire substrate coated with the AlN buffer layer into the MOCVD, pretreating it in an H2 atmosphere for 1 to 10 minutes at a treatment temperature of 1000 to 1200°C, and then nitriding the sapphire substrate to improve the crystal quality of the AlN buffer layer and effectively improve the crystal quality of the subsequently deposited GaN epitaxial layer.

[0051] S03, depositing a non-doped GaN layer 300 on the buffer layer 200;

[0052] Preferably, the thickness of the undoped GaN layer 300 is 1 μm to 5 μm, the growth temperature is 1050°C to 1200°C, and the pressure is 100 torr to 600 torr. The high growth temperature and low pressure of the undoped GaN layer 300 result in a GaN crystal of higher quality. At the same time, as the GaN thickness increases, compressive stress is released through stacking faults, reducing line defects, improving crystal quality, and reducing reverse leakage. However, increasing the thickness of the GaN layer consumes more Ga source material, significantly increasing the cost of LED epitaxy. Therefore, current LED epitaxial wafers typically grow undoped GaN at a thickness of 2 to 3 μm, which not only saves production costs but also ensures that the GaN material has higher crystal quality.

[0053] S04, depositing an N-type GaN layer 400 on the undoped GaN layer 300;

[0054] Preferably, the thickness of the N-type GaN layer 400 is 2 μm to 3 μm, the doping element of the N-type GaN layer 400 is Si, and the doping concentration of Si is 1×10 19 atoms / cm 3 ~5×10 19 atoms / cm 3 The N-type GaN layer 400 provides sufficient electrons for the LED to emit light. Secondly, the resistivity of the N-type GaN layer 400 is higher than that of the transparent electrode on the P-GaN. Therefore, sufficient Si doping can effectively reduce the resistivity of the N-type GaN layer 400. Combined with sufficient thickness of the N-type GaN, it can effectively release stress and improve the luminous efficiency of the light-emitting diode.

[0055] Furthermore, the growth temperature of the N-type GaN layer 400 is 1050° C. to 1200° C., and the pressure is 100 torr to 600 torr.

[0056] S05, depositing a multi-quantum well layer 500 on the N-type GaN layer 400;

[0057] Preferably, the multi-quantum well layer 500 has a V-shaped pit structure. The multi-quantum well layer 500 comprises alternating stacks of InGaN quantum well layers and AlGaN quantum barrier layers, with a stacking period of 6 to 12. The InGaN quantum well layer has a thickness of 2 nm to 5 nm and an In composition of 0.2 to 0.25, while the AlGaN quantum barrier layer has a thickness of 5 nm to 15 nm and an Al composition of 0.01 to 0.1. The multi-quantum well layer 500 is the region where electrons and holes recombine. A reasonable structural design can significantly increase the degree of overlap between electron and hole wave functions, thereby improving the luminous efficiency of LED devices.

[0058] Furthermore, the growth temperature of the InGaN quantum well layer is 790-810° C., and the pressure is 50-300 torr; the growth temperature of the AlGaN quantum barrier layer is 800-900° C., and the pressure is 50-300 torr.

[0059] S06, depositing a low-temperature P-type layer 600 on the multi-quantum well layer 500;

[0060] Preferably, the low-temperature P-type layer 600 includes an AlN layer 610, a Mg-AlInGaN layer 620 and a Mg-InGaN / AlGaN superlattice structure layer 630 stacked in sequence from bottom to top, and the Mg-InGaN / AlGaN superlattice structure layer 630 is a periodically alternating Mg-InGaN layer 631 and an AlGaN layer 632.

[0061] Furthermore, the growth temperature of the AlN layer 610 is 800°C to 900°C, exemplified by 800°C, 820°C, 840°C, 860°C, 880°C, and 900°C, but not limited thereto; the pressure is 50 torr to 500 torr, exemplified by 50 torr, 100 torr, 150 torr, 200 torr, 250 torr, 300 torr, 350 torr, 400 torr, 450 torr, and 500 torr, but not limited thereto; the growth atmosphere is N and NH3, and the flow ratio of N2 and NH3 is 1:(0.5-5), exemplified by 1:0.5, 1:1, 1:2, 1:3, 1:4, and 1:5, but not limited thereto.

[0062] Furthermore, the growth temperature of the Mg-AlInGaN layer 620 is 800°C to 900°C, exemplified by 800°C, 820°C, 840°C, 860°C, 880°C, and 900°C, but not limited thereto; the pressure is 50 torr to 500 torr, exemplified by 50 torr, 10 torr, 150 torr, 200 torr, 250 torr, 300 torr, 350 torr, 400 torr, 450 torr, and 500 torr, but not limited thereto; the growth atmosphere is N2 and NH3, and the flow ratio of N2 and NH3 is 1:(0.5-5), exemplified by 1:0.5, 1:1, 1:2, 1:3, 1:4, and 1:5, but not limited thereto.

[0063] Furthermore, the growth temperature of the Mg-InGaN layer 631 is 800°C to 900°C, exemplarily 800°C, 820°C, 840°C, 860°C, 880°C, and 900°C, but not limited thereto; the pressure is 50 torr to 500 torr, exemplarily 50 torr, 100 torr, 150 torr, 200 torr, 250 torr, 300 torr, 35 0torr, 400torr, 450torr, 500torr, but not limited to; the growth atmosphere is N2, NH3 and H2, and the flow ratio of N2, NH3 and H2 is 1:(1-5):(1-10), and exemplary are 1:1:1, 1:3:1, 1:5:1, 1:1:5, 1:1:10, 1:3:1, 1:3:10, 1:5:1, 1:5:10, but not limited to.

[0064] Furthermore, the growth temperature of the AlGaN layer 632 is 800°C to 900°C, exemplified by 800°C, 820°C, 840°C, 860°C, 880°C, and 900°C, but not limited thereto; the pressure is 50 torr to 500 torr, exemplified by 50 torr, 100 torr, 150 torr, 200 torr, 250 torr, 300 torr, 350 torr, 400 torr, 450 torr, and 500 torr, but not limited thereto; the growth atmosphere is N2 and NH3, and the flow ratio of N2 and NH3 is 1:(0.5-5), exemplified by 1:0.5, 1:1, 1:2, 1:3, 1:4, and 1:5, but not limited thereto.

[0065] S07, depositing an electron blocking layer 700 on the low-temperature P-type layer 600;

[0066] Preferably, the electron blocking layer 700 is an AlInGaN layer with an Al component of 0.01 to 0.1 and an In component of 0.01 to 0.2, which can effectively limit electron overflow and reduce the blocking of holes, thereby improving the injection efficiency of holes into the multi-quantum well layer 500, reducing carrier Auger recombination, and improving the luminous efficiency of the light-emitting diode.

[0067] Furthermore, the thickness of the electron blocking layer 700 is 10 nm to 40 nm.

[0068] Furthermore, the growth temperature of the electron blocking layer 700 is 900° C. to 1000° C., and the pressure is 100 torr to 300 torr.

[0069] S08, depositing a P-type GaN layer 800 on the electron blocking layer 700;

[0070] Preferably, the thickness of the P-type GaN layer 800 is 10 nm to 50 nm, the doping element of the P-type GaN layer 800 is Mg, and the doping concentration of Mg is 1×10 19 atoms / cm 3 ~1×10 21 atoms / cm 3 Too high a Mg doping concentration will damage the crystal quality, while too low a doping concentration will affect the hole concentration.

[0071] Furthermore, the growth temperature of the P-type GaN layer 800 is 900°C to 1050°C, and the growth pressure is 100 torr to 600 torr. For LED structures containing V-shaped pits, the higher growth temperature of the P-type GaN layer 800 is also conducive to further merging the V-shaped pits, resulting in a smooth surface of the LED epitaxial wafer.

[0072] The LED epitaxial wafer obtained in the present invention is used in LED products, which can increase the photoelectric efficiency of the LED products by 1% to 5%, and has good other electrical properties.

[0073] The present invention will be further described below with specific embodiments:

[0074] Example 1

[0075] This embodiment provides an epitaxial wafer for a light-emitting diode, comprising a substrate, on which are sequentially stacked a buffer layer, an undoped GaN layer, an N-type GaN layer, a multi-quantum well layer, a low-temperature P-type layer, an electron blocking layer, and a P-type GaN layer, wherein the multi-quantum well layer has a V-shaped pit structure; wherein the low-temperature P-type layer comprises an AlN layer, a Mg-AlInGaN layer, and a Mg-InGaN / AlGaN superlattice structure layer, which are sequentially stacked from bottom to top.

[0076] The thickness of the AlN layer is 3.5 nm;

[0077] The thickness of the Mg-AlInGaN layer is 6 nm, the Al composition is 0.06, the In composition is 0.05, and the Mg doping concentration is 6×10 18 atoms / cm 3 ;

[0078] The Mg-InGaN / AlGaN superlattice structure layer is a periodically alternating Mg-InGaN layer and an AlGaN layer, wherein the thickness of the Mg-InGaN layer is 3 nm, the In component in the Mg-InGaN layer is 0.05, and the Mg doping concentration is 1.5×10 20 atoms / cm 3 ; The thickness of the AlGaN layer is 4.5nm, the Al component is 0.05, the number of overlapping periods is 5, and the total thickness of the Mg-InGaN / AlGaN superlattice structure layer is 37.5nm.

[0079] It is prepared by the following preparation method:

[0080] S01. Providing a sapphire substrate;

[0081] S02, depositing a buffer layer on the substrate;

[0082] The buffer layer is an AlN buffer layer with a thickness of 15 nm. Specifically, the AlN buffer layer is deposited in an applied material PVD process, and then the sapphire substrate coated with the AlN buffer layer is transferred to an MOCVD process, pretreated in an H2 atmosphere for 5 minutes at a treatment temperature of 1100°C, and then the sapphire substrate is nitrided.

[0083] S03, depositing a non-doped GaN layer on the buffer layer;

[0084] The thickness of the non-doped GaN layer is 2 μm to 3 μm, the growth temperature is 1100° C., and the growth pressure is 150 Torr.

[0085] S04, depositing an N-type GaN layer on the undoped GaN layer;

[0086] The thickness of the N-type GaN layer is 2.5 μm, the doping element of the N-type GaN layer is Si, and the doping concentration of Si is 2.5×10 19 atoms / cm 3 , the growth temperature is 1120℃ and the pressure is 100torr.

[0087] S05, depositing a multi-quantum well layer on the N-type GaN layer;

[0088] The multi-quantum well layer is an alternately stacked InGaN quantum well layer and an AlGaN quantum barrier layer, with a stacking period of 10. The thickness of the InGaN quantum well layer is 3.5nm, the In component is 0.22, the growth temperature is 795°C, and the pressure is 200torr; the thickness of the AlGaN quantum barrier layer is 9.8nm, the Al component is 0.05, the growth temperature is 855°C, and the pressure is 200torr.

[0089] S06, depositing a low-temperature P-type layer on the multi-quantum well layer;

[0090] The low-temperature P-type layer includes an AlN layer, a Mg-AlInGaN layer, and a Mg-InGaN / AlGaN superlattice structure layer stacked sequentially from bottom to top, wherein the Mg-InGaN / AlGaN superlattice structure layer is a periodically alternating growth of Mg-InGaN layers and AlGaN layers;

[0091] The AlN layer is grown at a temperature of 845° C., a pressure of 100 torr, and a growth atmosphere of N 2 and NH 3 , with a flow ratio of N 2 to NH 3 of 1:2.

[0092] The growth temperature of the Mg-AlInGaN layer is 840° C., the pressure is 100 torr, the growth atmosphere is N2 and NH3, and the flow ratio of N2 to NH3 is 1:2.

[0093] The growth temperature of the Mg-InGaN layer is 840° C., the pressure is 100 torr, the growth atmosphere is N2, NH3 and H2, and the flow ratio of N2, NH3 and H2 is 1:1.5:5.

[0094] The AlGaN layer is grown at a temperature of 840° C., a pressure of 100 torr, and a growth atmosphere of N 2 and NH 3 , with a flow ratio of N 2 to NH 3 of 1:2.

[0095] S07, depositing an electron blocking layer on the low-temperature P-type layer;

[0096] The electron blocking layer is an AlInGaN layer, with an Al component of 0.1, an In component of 0.05, a thickness of 15 nm, a growth temperature of 965° C., and a pressure of 200 torr.

[0097] S08, depositing a P-type GaN layer on the electron blocking layer;

[0098] The thickness of the P-type GaN layer is 15 nm, the doping element of the P-type GaN layer is Mg, and the doping concentration of Mg is 2×10 20 atoms / cm 3 , the growth temperature is 985℃ and the growth pressure is 200torr.

[0099] Examples 2 to 9 and Comparative Examples 1 to 4 are substantially the same as Example 1, except for the relevant parameters of the low-temperature P-type layer 600. Specific relevant parameters of the low-temperature P-type layer 600 are shown in Table 1 below. The unit of thickness in the table is nm, and the unit of doping concentration is atoms / cm 3 .

[0100] Table 1 Parameter settings of the low temperature P-type layer in the embodiment and comparative example

[0101]

[0102] Performance Testing

[0103] The epitaxial wafers obtained in the embodiment and the comparative example were prepared into 10mil*24mil chips using the same chip process conditions. 300 LED chips were extracted from each sample and tested at a current of 120mA / 60mA. The test results are shown in Table 2 below, where the luminous efficiency improvement rate was calculated based on Comparative Example 1 which does not contain a low-temperature P-type layer.

[0104] Table 2 Test results of LED chips obtained in Examples and Comparative Examples

[0105] Improved lighting efficiency Improved lighting efficiency Example 1 5.0％ Example 8 3.9％ Example 2 2.5％ Example 9 3.1％ Example 3 3.8％ Example 10 1％ Example 4 3.3％ Comparative Example 1 0 Example 5 4.1％ Comparative Example 2 1.5％ Example 6 3.2％ Comparative Example 3 0.8％ Example 7 2.8％ Comparative Example 4 0.5％

[0106] From the above results, it can be seen that by setting a low-temperature P-type layer between the multi-quantum well layer and the electron blocking layer, the AlN layer, Mg-AlInGaN layer and Mg-InGaN / AlGaN superlattice structure layer cooperate with each other, which can reduce the dislocation between the bottom of the V-shaped pit in the multi-quantum well layer and the P-type layer, improve the crystal quality of the P-type layer, and at the same time improve the hole expansion efficiency and hole injection efficiency, reduce the leakage of the light-emitting diode, and thus improve the luminous efficiency of the LED.

[0107] The above disclosure is only a preferred embodiment of the present invention and certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. An epitaxial wafer of a light emitting diode, characterized in that: The invention comprises a substrate, a buffer layer, an undoped GaN layer, an N-type GaN layer, a multi-quantum well layer, a low-temperature P-type layer, an electron blocking layer and a P-type GaN layer sequentially stacked on the substrate; the multi-quantum well layer has a V-shaped pit structure; The low-temperature P-type layer includes an AlN layer, a Mg-AlInGaN layer, and a Mg-InGaN / AlGaN superlattice structure layer stacked sequentially from bottom to top; The Mg-InGaN / AlGaN superlattice structure layer is a periodically alternating Mg-InGaN layer and an AlGaN layer, the alternating period number being 1 to 20, and the AlGaN layer fills the V-shaped pit structure; The doping concentration of Mg in the Mg—AlInGaN layer is lower than the doping concentration of Mg in the Mg—InGaN layer.

2. The epitaxial wafer of a light emitting diode according to claim 1, wherein The Mg doping concentration in the Mg-AlInGaN layer is 1×10 18 ~1×10 19 atoms / cm 3 .

3. The epitaxial wafer of a light emitting diode according to claim 1, wherein: The Mg doping concentration in the Mg-InGaN layer is 1×10 19 ~1×10 21 atoms / cm 3 .

4. The epitaxial wafer of a light emitting diode according to claim 1, wherein The thickness of the AlN layer is 1-10 nm.

5. The epitaxial wafer of a light emitting diode according to claim 1, wherein: The thickness of the Mg-AlInGaN layer is 1-10 nm, the Al component is 0.01-0.1, and the In component is 0.01-0.

1.

6. The epitaxial wafer of a light emitting diode according to claim 1, wherein: The thickness of the Mg-InGaN layer is 0.5-5 nm, and the In composition is 0.01-0.1; The thickness of the AlGaN layer is 1-10 nm, and the Al composition is 0.01-0.

1.

7. The epitaxial wafer of a light emitting diode according to claim 1, wherein: The AlN layer is grown at a temperature of 800° C. to 900° C., a pressure of 50 torr to 500 torr, and a growth atmosphere of N2 and NH3, with a flow ratio of N2 to NH3 of 1:(0.5 to 5); The growth temperature of the Mg-AlInGaN layer is 800° C. to 900° C., the pressure is 50 torr to 500 torr, the growth atmosphere is N2 and NH3, and the flow ratio of N2 to NH3 is 1:1:(0.5 to 5); The growth temperature of the Mg-InGaN is 800° C. to 900° C., the pressure is 50 torr to 500 torr, the growth atmosphere is N2, NH3 and H2, and the flow ratio of N2 / NH3 / H2 is 1:(1-5):(1-10); The AlGaN layer is grown at a temperature of 800° C. to 900° C., a pressure of 50 torr to 500 torr, and a growth atmosphere of N2 and NH3, with a flow ratio of N2 to NH3 of 1:(0.5 to 5).

8. A method for preparing an epitaxial wafer of a light emitting diode according to any one of claims 1 to 7, characterized in that: include: S01. Providing a sapphire substrate; S02, depositing a buffer layer on the substrate; S03, depositing a non-doped GaN layer on the buffer layer; S04, depositing an N-type GaN layer on the undoped GaN layer; S05, depositing a multi-quantum well layer on the N-type GaN layer; S06, depositing a low-temperature P-type layer on the multi-quantum well layer; S07, depositing an electron blocking layer on the low-temperature P-type layer; S08, depositing a P-type GaN layer on the electron blocking layer; The low-temperature P-type layer includes an AlN layer, a Mg-AlInGaN layer and a Mg-InGaN / AlGaN superlattice structure layer stacked sequentially from bottom to top, and the Mg-InGaN / AlGaN superlattice structure layer is a periodically alternating growth of Mg-InGaN layers and AlGaN layers.

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