Light-emitting diode epitaxial wafer and preparation method thereof

Abstract

The present invention provides a light-emitting diode epitaxial wafer and a method for fabricating the same. The light-emitting diode epitaxial wafer comprises a substrate, and a buffer layer, a three-dimensional nucleation layer, an undoped GaN layer, an N-type GaN layer, a multi-quantum well layer, an electron blocking layer, and a P-type GaN layer sequentially deposited on the substrate. The three-dimensional nucleation layer comprises a stacked first and second three-dimensional nucleation sublayers, the thickness of the first three-dimensional nucleation sublayer being less than that of the second three-dimensional nucleation sublayer, both being MgGaN layers, and the growth temperature of the second three-dimensional nucleation sublayer being 10 to 100°C higher than that of the first three-dimensional nucleation sublayer. This light-emitting diode epitaxial wafer can increase the density of V-pits, improve carrier injection efficiency, and enhance the optoelectronic performance of the light-emitting diode.

Description

Technical Field

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

[0002] Light-emitting diodes (LEDs) are electroluminescent devices with advantages such as energy saving, environmental protection, safety, long life, low power consumption, high brightness, waterproofness, miniaturization, concentrated light beam, and easy maintenance. They are widely used in traffic lights, streetlights, and large-area displays. In particular, the rapid development of gallium nitride (GaN)-based LEDs has made white light illumination based on blue LEDs a research hotspot.

[0003] There are a lot of V-shaped pits in GaN-based light-emitting diodes. Currently, GaN-based LEDs are usually grown on sapphire, SiC and Si substrates. Because there is a lot of lattice mismatch and thermal mismatch between GaN and the substrate, the threading dislocation density in GaN-based LED devices is as high as 10 8 -10 10 / cm 2 , so these threading dislocations lead to the formation of V-pits. Previously, people believed that the V-pits produced in GaN-based light-emitting diodes had a negative impact on the optoelectronic performance of the light-emitting diodes, but the latest research shows that V-pits help to prevent carriers from being non-positive and also have the effect of shielding dislocations.

[0004] Currently, the main method for growing V-pits in GaN-based light-emitting diodes is to grow a low-temperature GaN layer in the epitaxial layer of the light-emitting diode. The high carbon content of the low-temperature GaN layer can induce the growth of V-pits. However, this method causes V-pits to form at different thicknesses of the low-temperature GaN layer, resulting in a low density of V-pits in the GaN-based light-emitting diode, affecting the carrier injection efficiency of the light-emitting diode and reducing the photoelectric performance of the light-emitting diode. Summary of the Invention

[0005] Based on this, the purpose of the present invention is to provide a light-emitting diode epitaxial wafer and a preparation method thereof, so as to increase the density of V-pits, improve the injection efficiency of carriers, and enhance the photoelectric performance of light-emitting diodes.

[0006] A light-emitting diode epitaxial wafer comprises: a substrate, and a buffer layer, a three-dimensional nucleation layer, an undoped GaN layer, an N-type GaN layer, a multi-quantum well layer, an electron blocking layer, and a P-type GaN layer sequentially deposited on the substrate, wherein the three-dimensional nucleation layer comprises a first three-dimensional nucleation sublayer and a second three-dimensional nucleation sublayer stacked together, the thickness of the first three-dimensional nucleation sublayer being less than that of the second three-dimensional nucleation sublayer, the first three-dimensional nucleation sublayer and the second three-dimensional nucleation sublayer being both MgGaN layers, and the growth temperature of the second three-dimensional nucleation sublayer being 10 to 100° C. higher than the growth temperature of the first three-dimensional nucleation sublayer.

[0007] Furthermore, in the above-mentioned light-emitting diode epitaxial wafer, the total thickness of the first three-dimensional nucleation sublayer and the second three-dimensional nucleation sublayer is 0.5um to 5um.

[0008] Furthermore, in the above-mentioned light-emitting diode epitaxial wafer, the total content of Mg components in the first three-dimensional nucleation sublayer and the second three-dimensional nucleation sublayer is 0.01 to 0.1.

[0009] Furthermore, in the above-mentioned light-emitting diode epitaxial wafer, the thickness ratio of the first three-dimensional nucleation sublayer to the second three-dimensional nucleation sublayer is 1:2 to 1:10.

[0010] Furthermore, in the above-mentioned light-emitting diode epitaxial wafer, the first three-dimensional nucleation sublayer and the second three-dimensional nucleation sublayer are grown in a mixed atmosphere of N2, H2 and NH3, and the ratio of N2, H2 and NH3 in the mixed atmosphere is 2:4:1 to 2:8:1.

[0011] Furthermore, in the above-mentioned light-emitting diode epitaxial wafer, the growth temperature of the first three-dimensional nucleation sublayer is 900-1100°C.

[0012] Furthermore, in the above-mentioned light-emitting diode epitaxial wafer, the thickness of the N-type GaN layer is 2 to 3 μm.

[0013] Furthermore, in the above-mentioned light-emitting diode epitaxial wafer, the Si doping concentration in the N-type GaN layer is 1E19 to 5E19 atoms / cm 3 .

[0014] Furthermore, in the above-mentioned light-emitting diode epitaxial wafer, the electron blocking layer is Al x In y Ga 1-x-y N, its thickness is 10~40nm, of which 0.005 <x<0.1,0.05<y<0.2。

[0015] Furthermore, in the above-mentioned light-emitting diode epitaxial wafer, the thickness of the P-type GaN layer is 10 to 50 nm, and the Mg doping concentration is 1E+19 to 1E+21 atoms / cm 3 .

[0016] The present invention also provides a method for preparing a light-emitting diode epitaxial wafer, comprising:

[0017] providing a substrate;

[0018] depositing a buffer layer on the substrate;

[0019] Pre-treating the substrate with the buffer layer deposited thereon in a H2 atmosphere;

[0020] Depositing a first three-dimensional nucleation sublayer and a second three-dimensional nucleation sublayer in sequence on the buffer layer, wherein the thickness of the first three-dimensional nucleation sublayer is less than that of the second three-dimensional nucleation sublayer, the first three-dimensional nucleation sublayer and the second three-dimensional nucleation sublayer are both MgGaN layers, and the growth temperature of the second three-dimensional nucleation sublayer is 10 to 100° C. higher than the growth temperature of the first three-dimensional nucleation sublayer;

[0021] depositing an undoped GaN layer on the second three-dimensional nucleation sublayer;

[0022] Depositing an N-type GaN layer on the undoped GaN layer;

[0023] depositing a multi-quantum well layer on the N-type GaN layer;

[0024] depositing an electron blocking layer on the multi-quantum well layer;

[0025] A P-type GaN layer is deposited on the electron blocking layer.

[0026] Furthermore, in the above preparation method, the growth temperature of the first three-dimensional nucleation sublayer is 900-1100°C.

[0027] Furthermore, in the above preparation method, the growth pressure of the first three-dimensional nucleation sublayer and the second three-dimensional nucleation sublayer is 100 to 500 torr.

[0028] Furthermore, in the above-mentioned preparation method, the first three-dimensional nucleation sublayer and the second three-dimensional nucleation sublayer are grown in a mixed atmosphere of N2, H2 and NH3, and the ratio of N2, H2 and NH3 in the mixed atmosphere is 2:4:1 to 2:8:1.

[0029] In the present invention, the undoped layer is grown on the three-dimensional nucleation layer. The three-dimensional nucleation layer introduces a Mg component, which increases the density of threading dislocations in the epitaxial layer. The density of V-pits is closely related to the density of threading dislocations. Therefore, the increased density of V-pits improves the hole injection efficiency, thereby improving the photoelectric efficiency of the light-emitting diode. The three-dimensional nucleation layer includes a first three-dimensional nucleation sublayer and a second three-dimensional nucleation sublayer, with a thickness ratio of 1:2 to 1:10. The density of nucleation islands on the first three-dimensional nucleation sublayer is low, which can slow the merging rate of islands, reduce the density of defects, and improve the crystal quality of the GaN epitaxial layer. The nucleation islands on the second three-dimensional nucleation sublayer grow faster laterally, grow rapidly, and fuse, promoting the growth of the undoped GaN layer, increasing the lateral mobility of GaN, promoting the two-dimensional growth of GaN to fill the three-dimensional nucleation layer, and improving the crystal quality of GaN. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the structure of a light-emitting diode epitaxial wafer according to an embodiment of the present invention;

[0031] Figure 2 Flowchart of a method for preparing a light-emitting diode epitaxial wafer according to an embodiment of the present invention.

[0032] Description of main component symbols:

[0033] 10: substrate, 20: buffer layer, 30: three-dimensional nucleation layer, 31: first three-dimensional nucleation sublayer, 32: second three-dimensional nucleation sublayer, 40: non-Si-doped GaN layer, 50: N-type GaN layer, 60: multiple quantum well layer, 70: electron blocking layer, 80: P-type GaN layer.

[0034] The following specific embodiments will further illustrate the invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0035] To facilitate understanding of the present invention, the present invention will be described more fully below with reference to the accompanying drawings. The drawings illustrate several embodiments of the present invention. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the present invention.

[0036] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be an intermediate element. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used in this specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0038] Example 1

[0039] See also Figure 1 , shown is a light-emitting diode epitaxial wafer in embodiment 1 of the present invention, including: a substrate 10, and a buffer layer 20, a three-dimensional nucleation layer 30, an undoped GaN layer 40, an N-type GaN layer 50, a multi-quantum well layer 60, an electron blocking layer 70 and a P-type GaN layer 80 deposited on the substrate 10 from bottom to top.

[0040] The substrate 10 can be selected from one of a sapphire substrate, a SiO2 substrate, a silicon substrate, a silicon carbide substrate, a gallium nitride substrate, and a zinc oxide substrate.

[0041] Specifically, in this embodiment, a sapphire substrate is selected as the substrate 10. The sapphire substrate has a mature preparation process, is relatively low in price, is easy to clean and process, and has good stability at high temperatures.

[0042] A buffer layer 20 is deposited on the substrate 10. Specifically, an AlN buffer layer is deposited in an applied material PVD process. The buffer layer 20 may have a thickness of 10 to 50 nm.

[0043] In this embodiment, the thickness of the buffer layer 20 is specifically 15 nm. Epitaxial growth is performed using an A7 MOCVD (Metal-organic Chemical Vapor Deposition, MOCVD) device, with high-purity H2 (hydrogen), high-purity N2 (nitrogen), or at least one of high-purity H2 and high-purity N2 as a carrier gas, high-purity NH3 as an N source, trimethylgallium (TMGa) and triethylgallium (TEGa) as gallium sources, trimethylindium (TMIn) as an indium source, trimethylaluminum (TMAl) as an aluminum source, silane (SiH4) as an N-type dopant, and bis(cyclopentadienyl)magnesium (CP2Mg) as a P-type dopant.

[0044] The three-dimensional nucleation layer 30 includes a first three-dimensional nucleation sublayer 31 and a second three-dimensional nucleation sublayer 32 sequentially stacked on the buffer layer 20. The first three-dimensional nucleation sublayer 31 and the second three-dimensional nucleation sublayer 32 are both MgGaN layers, and the total content of Mg components in the first three-dimensional nucleation sublayer 31 and the second three-dimensional nucleation sublayer 32 is 0.001 to 0.1. It should be noted that the content of the Mg component is closely related to the nucleation density of the three-dimensional nucleation layer. If the Mg component content is too low, it will lead to too few nucleation centers, resulting in a lower density of threading dislocations generated by the subsequent merging of the three-dimensional nucleation layers, and a lower density of V-shaped pits. If the Mg component content is too high, the impurity atom content is too high, which will destroy the crystal quality of the GaN epitaxial layer, resulting in a decrease in the luminous efficiency and electrical performance of the light-emitting diode.

[0045] Furthermore, the growth temperature of the second three-dimensional nucleation sublayer 32 is 10 to 100°C higher than that of the first three-dimensional nucleation sublayer 31. The different growth temperatures of the first and second three-dimensional nucleation sublayers 31 and 32 result in two sublayers with different properties. The first three-dimensional nucleation sublayer 31 is formed by the deposition of GaN nuclei, while the second three-dimensional nucleation sublayer 32 is formed by the continued growth of GaN nuclei into GaN islands. Their growth is closely related to temperature. At higher temperatures, the lateral growth of the second three-dimensional nucleation sublayer 32 is greater than its vertical growth, and the GaN islands in the three-dimensional nucleation layers merge.

[0046] These two sublayers also play different roles in the growth of the diode epitaxial wafer. The first 3D nucleation sublayer 31 primarily controls the GaN nucleation density; a thicker thickness results in a lower nucleation density. The second 3D nucleation sublayer 32 controls the lateral growth rate of the 3D nucleation layer, promoting the rapid growth and fusion of the GaN islands in the nucleation layer, thereby improving the crystal quality of the GaN layer.

[0047] Furthermore, the thickness of the three-dimensional nucleation layer 30 is 0.5um to 5um, and the thickness ratio of the first three-dimensional nucleation sublayer 31 to the second three-dimensional nucleation sublayer 32 is 1:2 to 1:10. The lower the thickness ratio of the first three-dimensional nucleation sublayer, the higher the density of the nucleated GaN islands in the three-dimensional GaN nucleation layer, the higher the density of threading dislocations formed, and the higher the density of V-pits formed subsequently; the higher the thickness ratio of the first three-dimensional nucleation sublayer, the lower the density of the nucleated GaN islands, the lower the density of threading dislocations, and the lower the density of V-pits formed subsequently. As the thickness ratio of the second three-dimensional nucleation sublayer increases, the lateral and transverse growth rates gradually increase, accelerating the growth and fusion of the GaN islands in the three-dimensional nucleation layer and improving the crystal quality of GaN.

[0048] Specifically, in this embodiment, the total Mg component in the first three-dimensional nucleation sublayer 31 and the second three-dimensional nucleation sublayer 32 is 0.05, and the total thickness is 2um, wherein the thickness of the first three-dimensional nucleation sublayer 31 is 0.4um, and the thickness of the second three-dimensional nucleation sublayer 32 is 1.6um.

[0049] The undoped GaN layer 40 is deposited on the three-dimensional nucleation layer 30 and may have a thickness of 1 to 5 μm.

[0050] Specifically, as GaN grows thicker, its crystal quality improves, but the Ga source consumes more and is more expensive. Taking all factors into consideration, in this embodiment, the thickness of the undoped GaN layer 40 is 2.5 μm. This thickness not only improves the GaN crystal quality, but also saves Ga source and reduces production costs.

[0051] The N-type GaN layer 50 is deposited on the undoped GaN layer 40 , and has a thickness of 2 to 3 μm and a Si doping concentration of 1E19 to 5E19 atoms / cm 3 .

[0052] Specifically, in this embodiment, the N-type GaN layer 50 is grown to a thickness of 2.5 μm and the Si doping concentration is 2.5E19 atoms / cm 3 At this thickness and Si doping concentration, the N-type GaN interface resistance is 12Ω·cm 2 , which is equivalent to the contact resistance between the P layer and ITO, reduces the current concentration effect and helps current expansion.

[0053] The multi-quantum well layer 60 is deposited on the N-type GaN layer 50. The multi-quantum well layer 60 is composed of alternating InGaN quantum well layers and AlGaN quantum barrier layers, with 6 to 12 stacking periods. The InGaN quantum well layer has a thickness of 2 to 5 nm and a growth pressure of 100 to 300 torr. The AlxGa1-xN quantum barrier layer has a growth temperature of 800 to 900°C, a thickness of 8 to 12 nm, a growth pressure of 100 to 300 torr, and an Al content of 0.01 to 0.1.

[0054] Specifically, in this embodiment, the number of stacking periods of the InGaN quantum well layer and the AlGaN quantum barrier layer in the multi-quantum well layer 60 is 10. Moreover, the thickness of the InGaN quantum well is 3.5 nm, the thickness of the AlGaN quantum barrier layer is 9.8 nm, and the Al composition is 0.05.

[0055] The electron blocking layer 70 is grown on the multi-quantum well layer 60. Optionally, the electron blocking layer 70 is Al x In y Ga 1-x- yThe N has a thickness of 10 - 40 nm, a growth temperature of 900 - 1000 °C, a pressure of 100 - 300 torr, where the Al component is 0.005 < x < 0.1 and the In component concentration is 0.05 < y < 0.2.

[0056] Specifically, in this embodiment, the electron blocking layer 70 is Al 0.05 In 0.1 Ga 0.85 N, with a thickness of 15 nm. The electron blocking layer 70 can effectively limit electron overflow and also reduce the blocking of holes.

[0057] The P-type GaN layer 80 is deposited on the electron blocking layer 70, with a thickness of 10 - 50 nm. The PGaN layer is doped with Mg, and the doping concentration of Mg is 1E+19 - 1E+21 atoms / cm 3 .

[0058] Specifically, in this embodiment, the P-type GaN layer 80 has a thickness of 15 nm and a Mg doping concentration of 2E+20 atoms / cm 3 .

[0059] In this embodiment, the undoped layer is grown on the three-dimensional nucleation layer. The three-dimensional nucleation layer introduces the Mg component, increasing the density of threading dislocations in the epitaxial layer. Since the density of V-shaped pits is closely related to the density of threading dislocations, the density of V-shaped pits increases, the hole injection efficiency is improved, and the optoelectronic efficiency of the light-emitting diode is enhanced. The three-dimensional nucleation layer includes a first three-dimensional nucleation sub-layer and a second three-dimensional nucleation sub-layer, and the thickness ratio between the two is 1:2 - 1:10. The density of nucleation islands on the first three-dimensional nucleation sub-layer is relatively low, which can slow down the merging speed of the islands, reduce the density of defects, and improve the crystal quality of the GaN epitaxial layer. The lateral growth of the nucleation islands on the second three-dimensional nucleation sub-layer is relatively fast, and the nucleation islands grow and fuse rapidly, promoting the growth of the undoped GaN layer, increasing the lateral mobility of GaN, promoting the two-dimensional growth of GaN to fill the three-dimensional nucleation layer, and improving the crystal quality of GaN.

[0060] Please refer to Figure 2 , which is the preparation method of the light-emitting diode epitaxial wafer in the embodiment of the present invention, including steps S01 to S09.

[0061] Step S01, provide a substrate.

[0062] The substrate can be selected from one of sapphire substrates, SiO2 substrates, silicon substrates, silicon carbide substrates, gallium nitride substrates, and zinc oxide substrates.

[0063] Specifically, in this embodiment, the sapphire substrate is selected as the substrate because the sapphire substrate has mature preparation processes, low prices, is easy to clean and process, and has good stability at high temperatures.

[0064] Step S02: depositing a buffer layer on the substrate.

[0065] In this embodiment, an AlN buffer layer with a thickness of 15 nm was deposited using an Applied Materials PVD process. Specifically, an A7 MOCVD (Metal-organic Chemical Vapor Deposition) device was used. At least one of high-purity H2 and high-purity N2 was used as the carrier gas for growing the buffer layer. High-purity NH3 was used as the N source. Trimethylgallium (TMGa) and triethylgallium (TEGa) were used as the gallium source. Trimethylindium (TMIn) was used as the indium source. Trimethylaluminum (TMAl) was used as the aluminum source. Silane (SiH4) was used as the N-type dopant. CP2Mg was used as the P-type dopant for epitaxial growth.

[0066] Step S03 , pre-treating the substrate on which the buffer layer is deposited in an H 2 atmosphere.

[0067] Specifically, the sapphire substrate coated with the AlN buffer layer is transferred into the MOCVD process, pretreated in an H2 atmosphere for 1 to 10 minutes at a treatment temperature of 1000 to 1200° C., and then the sapphire substrate is nitrided.

[0068] Step S04: Depositing a first three-dimensional nucleation sublayer and a second three-dimensional nucleation sublayer in sequence on the buffer layer. The thickness ratio of the first three-dimensional nucleation sublayer to the second three-dimensional nucleation sublayer is 1:2 to 1:10. The first three-dimensional nucleation sublayer and the second three-dimensional nucleation sublayer are both MgGaN layers, and the total Mg content in the first three-dimensional nucleation sublayer and the second three-dimensional nucleation sublayer is 0.001 to 0.1.

[0069] Optionally, the growth temperature of the first three-dimensional nucleation sublayer is 900-1100° C., and the growth temperature of the second three-dimensional nucleation sublayer is 10-100° C. higher than the growth temperature of the first three-dimensional nucleation sublayer.

[0070] Optionally, the growth pressure of the first three-dimensional nucleation sublayer and the second three-dimensional nucleation sublayer is 100 to 500 torr.

[0071] Optionally, the first three-dimensional nucleation sublayer and the second three-dimensional nucleation sublayer are grown in a mixed atmosphere of N2, H2 and NH3, and the ratio of N2, H2 and NH3 in the mixed atmosphere is 2:4:1 to 2:8:1.

[0072] Specifically, in this embodiment, the total Mg content of the first and second three-dimensional nucleation sublayers is 0.05, and the total thickness is 2 μm. The thickness of the first three-dimensional nucleation sublayer is 0.4 μm, and the thickness of the second three-dimensional nucleation sublayer is 1.6 μm. The growth temperature of the first three-dimensional nucleation sublayer is 1050°C, and the growth temperature of the second three-dimensional nucleation sublayer is 1080°C. The growth pressure of the three-dimensional nucleation layer is 150 Torr, and the growth atmosphere has an N2 / H2 / NH3 ratio of 2:6:1.

[0073] Step S05 : depositing an undoped GaN layer on the second three-dimensional nucleation sublayer.

[0074] Optionally, the undoped GaN layer is grown at a temperature of 1050° C. to 1200° C., a pressure of 100 torr to 600 torr, and a thickness of 1 to 5 um.

[0075] Specifically, in this embodiment, the undoped GaN layer is grown at a temperature of 1100°C and a pressure of 150 Torr. As GaN grows thicker, its crystal quality improves, but its cost also increases. In this embodiment, the undoped GaN layer is grown to a thickness of 2.5 μm, which not only improves the GaN crystal quality but also saves Ga source and reduces production costs.

[0076] Step S06 , depositing an N-type GaN layer on the undoped GaN layer.

[0077] Optionally, the N-type GaN layer is grown at a temperature of 1050°C to 1200°C, a pressure of 100 to 600 torr, a thickness of 2 to 3 μm, and a Si doping concentration of 1E19 to 5E19 atoms / cm 3 .

[0078] Specifically, in this embodiment, the N-type GaN layer is grown at a temperature of 1120°C, a pressure of 100 Torr, a thickness of 2.5 μm, and a Si doping concentration of 2.5E19 atoms / cm 3 At this thickness and Si doping concentration, the n-type GaN interface resistance is 12Ω·cm2, which is equivalent to the contact resistance between the P layer and ITO, reducing the current crowding effect and facilitating current expansion.

[0079] Step S07 , depositing a multi-quantum well layer on the N-type GaN layer.

[0080] Optionally, the multi-quantum well layer is an alternately stacked InGaN quantum well layer and an AlGaN quantum barrier layer, with a stacking period of 6 to 12, wherein the InGaN quantum well layer is grown at a temperature of 790 to 810°C, a thickness of 2 to 5 nm, a growth pressure of 100 torr to 300 torr, and the AlGaN layer is grown at a temperature of 100 to 300 torr to achieve a thickness of 2 to 5 nm. x Ga 1-xThe growth temperature of the N quantum barrier layer is 800 - 900 °C, the thickness is 8 - 12 nm, the growth pressure is 100 - 300 torr, and the Al component is 0.01 - 0.1.

[0081] Specifically, in this embodiment, the number of alternating stacks of InGaN quantum well layers and AlGaN quantum barrier layers is 10. Among them, the growth temperature of the InGaN quantum well is 795 °C, the thickness is 3.5 nm, and the pressure is 200 torr. The growth temperature of the AlGaN quantum barrier layer is 855 °C, the thickness is 9.8 nm, the growth pressure is 200 torr, and the Al component is 0.05.

[0082] Step S08, depositing an electron blocking layer on the multiple quantum well layer.

[0083] Optionally, the electron blocking layer is Al x In y Ga 1-x-y N with a thickness of 10 - 40 nm, a growth temperature of 900 - 100 °C, a pressure of 100 - 300 torr, where the Al component is 0.005 < x < 0.1 and the In component concentration is 0.05 < y < 0.2.

[0084] Specifically, in this embodiment, the electron blocking layer is Al 0.05 In 0.1 Ga 0.85 N, with a thickness of 15 nm, a growth temperature of 965 °C, and a growth pressure of 200 torr. This electron blocking layer can effectively limit electron overflow and reduce the blocking of holes.

[0085] Step S09, depositing a P-type GaN layer on the electron blocking layer.

[0086] Optionally, the growth temperature of the P-type GaN layer is 900 - 1050 °C, the thickness is 10 - 50 nm, the growth pressure is 100 - 600 torr, and the Mg doping concentration is 1E+19 - 1E+21 atoms / cm 3 。

[0087] Specifically, in this embodiment, the growth temperature of the P-type GaN layer is 985 °C, the thickness is 15 nm, the growth pressure is, 200 torr, and the Mg doping concentration is 2E+20 atoms / cm 3 。

[0088] In this embodiment, a three-dimensional nucleation layer is grown before the undoped layer. The three-dimensional nucleation layer is composed of MgGaN, with a Mg content of 0.01 to 0.1. The introduction of Mg into the three-dimensional nucleation layer increases the density of threading dislocations in the epitaxial layer. The density of V-pits is closely related to the density of threading dislocations. Therefore, the increased density of V-pits improves the hole injection efficiency, thereby enhancing the photoelectric efficiency of the light-emitting diode. The growth temperature of the three-dimensional nucleation layer is 900 to 1100°C, with the growth temperature of the second three-dimensional nucleation sublayer being 10 to 100°C higher than that of the first three-dimensional nucleation sublayer. The lower growth temperature of the first three-dimensional nucleation sublayer results in a lower density of nucleation islands, slowing the merging of islands and reducing the density of defects, thereby improving the crystal quality of the GaN epitaxial layer. The slightly higher growth temperature of the second nucleation layer accelerates the lateral growth of the nucleation islands, allowing the islands to continue to grow and fuse. The three-dimensional nucleation layer growth pressure is 100 to 500 torr, and the N2 / H2 / NH3 ratio in the mixed growth atmosphere is between 2:4:1 and 2:8:1. During the initial stages of 3D nucleation layer growth, reducing the V / III ratio can enhance 3D growth and increase the size of the GaN islands. The V / III ratio refers to the ratio of NH3 to Ga source. A decrease in the NH3 ratio reduces island density and delays island merging, thereby reducing the density of line defects and improving the crystal quality of the GaN epitaxial layer. This 3D nucleation layer growth pattern can effectively improve the photoelectric efficiency of light-emitting diodes.

[0089] Example 2

[0090] The structure of the light-emitting diode epitaxial wafer in this embodiment is basically the same as that in the first embodiment, except that:

[0091] The thickness ratio of the first three-dimensional nucleation sublayer to the second three-dimensional nucleation sublayer is 1:2.

[0092] Example 3

[0093] The structure of the light-emitting diode epitaxial wafer in this embodiment is basically the same as that in the first embodiment, except that:

[0094] The thickness ratio of the first three-dimensional nucleation sublayer to the second three-dimensional nucleation sublayer is 1:10.

[0095] Example 4

[0096] The structure of the light-emitting diode epitaxial wafer in this embodiment is basically the same as that in the first embodiment, except that:

[0097] The thickness of the three-dimensional nucleation layer is 2 μm, that is, the total thickness of the first three-dimensional nucleation sublayer and the second three-dimensional nucleation sublayer is 2 μm.

[0098] Example 5

[0099] The structure of the light-emitting diode epitaxial wafer in this embodiment is basically the same as that in the first embodiment, except that:

[0100] The ratio of N2, H2 and NH3 in the growth atmosphere of the three-dimensional nucleation layer is 2:4:1.

[0101] Example 6

[0102] The structure of the light-emitting diode epitaxial wafer in this embodiment is basically the same as that in the first embodiment, except that:

[0103] The ratio of N2, H2 and NH3 in the growth atmosphere of the three-dimensional nucleation layer is 2:8:1.

[0104] Example 7

[0105] The structure of the light-emitting diode epitaxial wafer in this embodiment is basically the same as that in the first embodiment, except that:

[0106] The total content of Mg components in the three-dimensional nucleation layer is 0.03.

[0107] Example 8

[0108] The structure of the light-emitting diode epitaxial wafer in this embodiment is basically the same as that in the first embodiment, except that:

[0109] The total content of Mg components in the three-dimensional nucleation layer is 0.07, and the ratio of N2, H2 and NH3 in the growth atmosphere of the three-dimensional nucleation layer is 2:8:1.

[0110] Comparative Example 1

[0111] The structure of the light-emitting diode epitaxial wafer in this embodiment is basically the same as that in the first embodiment, except that:

[0112] In this embodiment, no Mg is added to the three-dimensional nucleation layer.

[0113] Comparative Example 2

[0114] The structure of the light-emitting diode epitaxial wafer in this embodiment is basically the same as that in the first embodiment, except that:

[0115] In this embodiment, no Mg is added to the three-dimensional nucleation layer, and the temperature during the growth of the three-dimensional nucleation layer remains constant at 1050° C., that is, the first three-dimensional nucleation sublayer and the second three-dimensional nucleation sublayer are not formed in this embodiment.

[0116] Please refer to Table 1 below, which shows the parameters corresponding to the above-mentioned Examples 1 to 8 and Comparative Examples 1-2 of the present invention.

[0117] Table 1

[0118]

[0119]

[0120] Examples 1 through 8, as well as Comparative Examples 1 and 2, were fabricated using the same chip processing conditions into 10 mil x 24 mil chips. 300 LED chips were sampled from each chip and tested at 120 mA / 60 mA. The luminous efficacy improvement compared to conventional chips is shown in Table 2. Combining the data in Tables 1 and 2 clearly demonstrates that the technical solutions in the embodiments of the present invention can significantly improve luminous efficacy, by 0.1% to 1% compared to conventional chips, while maintaining good electrical performance.

[0121] From Comparative Examples 1 to 2, it can be seen that when Mg is not added to the three-dimensional nucleation layer, or when the first three-dimensional nucleation sublayer and the second three-dimensional nucleation sublayer are not formed, the luminous efficiency is unchanged compared with the conventional chip, that is, the luminous efficiency is not improved.

[0122] Table 2

[0123]

[0124] Through the structural design of this embodiment of the present invention, the light-emitting diode epitaxial wafer can effectively increase the density of V-shaped pits, improve the injection efficiency of carriers, and enhance the photoelectric performance of the light-emitting diode.

[0125] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0126] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A light-emitting diode epitaxial wafer, characterized in that: include: A substrate, and a buffer layer, a three-dimensional nucleation layer, an undoped GaN layer, an N-type GaN layer, a multi-quantum well layer, an electron blocking layer and a P-type GaN layer deposited in sequence on the substrate, wherein the three-dimensional nucleation layer includes a stacked first three-dimensional nucleation sublayer and a second three-dimensional nucleation sublayer, the thickness of the first three-dimensional nucleation sublayer is less than the thickness of the second three-dimensional nucleation sublayer, the first three-dimensional nucleation sublayer and the second three-dimensional nucleation sublayer are both MgGaN layers, the growth temperature of the second three-dimensional nucleation sublayer is 10 to 100° C. higher than the growth temperature of the first three-dimensional nucleation sublayer, the total thickness of the first three-dimensional nucleation sublayer and the second three-dimensional nucleation sublayer is 0.5 μm to 5 μm, and the thickness ratio of the first three-dimensional nucleation sublayer to the second three-dimensional nucleation sublayer is 1:2 to 1:

10.

2. The light emitting diode epitaxial wafer according to claim 1, wherein: The total content of Mg components in the first three-dimensional nucleation sublayer and the second three-dimensional nucleation sublayer is 0.01-0.

1.

3. The light emitting diode epitaxial wafer according to claim 1, wherein: The growth temperature of the first three-dimensional nucleation sublayer is 900-1100°C.

4. The light emitting diode epitaxial wafer according to claim 1, wherein: The first three-dimensional nucleation sublayer and the second three-dimensional nucleation sublayer are grown in a mixed atmosphere of N2, H2 and NH3, and the ratio of N2, H2 and NH3 in the mixed atmosphere is 2:4:1 to 2:8:

1.

5. A method for preparing a light-emitting diode epitaxial wafer, characterized in that: include: providing a substrate; depositing a buffer layer on the substrate; Pre-treating the substrate with the buffer layer deposited thereon in a H2 atmosphere; A first three-dimensional nucleation sublayer and a second three-dimensional nucleation sublayer are sequentially deposited on the buffer layer, wherein the thickness of the first three-dimensional nucleation sublayer is less than the thickness of the second three-dimensional nucleation sublayer, the first three-dimensional nucleation sublayer and the second three-dimensional nucleation sublayer are both MgGaN layers, and the growth temperature of the second three-dimensional nucleation sublayer is 10 to 100° C. higher than the growth temperature of the first three-dimensional nucleation sublayer, the total thickness of the first three-dimensional nucleation sublayer and the second three-dimensional nucleation sublayer is 0.5 μm to 5 μm, and the thickness ratio of the first three-dimensional nucleation sublayer to the second three-dimensional nucleation sublayer is 1:2 to 1:10; depositing an undoped GaN layer on the second three-dimensional nucleation sublayer; Depositing an N-type GaN layer on the undoped GaN layer; depositing a multi-quantum well layer on the N-type GaN layer; depositing an electron blocking layer on the multi-quantum well layer; A P-type GaN layer is deposited on the electron blocking layer.

6. The preparation method according to claim 5, wherein The growth temperature of the first three-dimensional nucleation sublayer is 900-1100°C.

7. The preparation method according to claim 5, wherein The growth pressure of the first three-dimensional nucleation sublayer and the second three-dimensional nucleation sublayer is 100 torr to 500 torr.

8. The preparation method according to claim 5, wherein The first three-dimensional nucleation sublayer and the second three-dimensional nucleation sublayer are grown in a mixed atmosphere of N2, H2 and NH3, and the ratio of N2, H2 and NH3 in the mixed atmosphere is 2:4:1 to 2:8:1.

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