A method for growing a high luminous efficiency light emitting diode epitaxial wafer

Abstract

The present invention relates to the technical field of light-emitting diodes, and particularly relates to a method for growing a high-light-efficiency light-emitting diode epitaxial wafer, which includes: a substrate, a buffer layer is grown on the substrate, a U_GaN1 layer is grown thereon, a U_GaN2 layer is grown thereon, an NGaN layer and an LED full structure layer are grown thereon; wherein the U_GaN1 layer includes a 3D1 layer grown at a low temperature and a low growth rate, a recrystallization layer is grown thereon, and a 3D2 layer is grown thereon; wherein the temperature of the recrystallization layer is higher than that of the 3D1 layer, the NH3 of the recrystallization layer is less than that of the 3D1 layer, and the H2 is greater than that of the 3D1 layer. The present invention innovatively utilizes the different atmospheres of the recrystallization layer to decompose GaN on the C-plane / non-C-plane, thereby eliminating the proportion of non-C-plane GaN crystals. The 3D2 layer grown thereon has a high temperature and a high growth rate, mainly GaN crystals on the C-plane, which is beneficial to eliminating the dislocations in contact with the non-C-plane and reducing the generation of voids in the GaN crystals grown at the top of the patterned substrate, thereby improving the lattice quality of the epitaxial material and enhancing the light-emitting efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of light-emitting diodes, and particularly relates to a method for growing a high-light-efficiency light-emitting diode epitaxial wafer. Background Art

[0002] White LEDs have currently replaced traditional lighting and become the preferred method for general indoor and outdoor lighting. How to improve the luminous efficiency of light-emitting diodes (LEDs) has become an important issue to be solved. Due to the properties of the material itself, the mismatch stress in the epitaxial layer will introduce structural defects such as dislocations, stacking faults, and pores, deteriorating the crystal quality and thus reducing the luminous efficiency. How to improve the crystal quality of the epitaxial structure has become an important issue for improving the luminous efficiency of LEDs.

[0003] Currently, for LED epitaxial wafers with PSS patterned substrates, the dislocation density can be well reduced and the luminous efficiency can be improved. However, in the actual 3D growth process, a small amount of GaN crystals will also be generated on the non-polar surface of Al2O3, and will contact the GaN crystals grown on the C plane at the top and below the substrate pattern, resulting in the following: 1. Due to the different polarities of the two GaN, the atoms at the interface are not easy to bond, thus generating new dislocations or increasing the polarization effect at the interface due to the different polarities of GaN; 2. When the GaN crystals fill and cover the top of the substrate pattern, holes may be formed in the substrate pattern and its top region, thus affecting the luminous efficiency. Summary of the Invention

[0004] In order to overcome the problems existing in the background art, the present invention has developed a method for growing a high-light-efficiency light-emitting diode epitaxial wafer, and its purpose is: by inserting a recrystallization layer in the 3D layer to eliminate the generation of GaN crystals on non-C planes, and cracking the GaN crystals generated on non-C planes of the patterned substrate through the recrystallization layer, avoiding or reducing the generation of GaN crystals on non-C planes, and reducing the dislocations or polarization effects generated when GaN crystals with different polarities bond: maximizing the contact and bonding of the GaN crystals grown on the C plane at the top of the substrate pattern, reducing the formation of voids in the substrate pattern and its top region, reducing the generation of dislocations and improving the lattice quality of the epitaxial layer, thereby improving the luminous efficiency.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for growing a high-light-efficiency light-emitting diode epitaxial wafer, comprising: a substrate, growing a buffer layer on the substrate, growing a U_GaN1 layer thereon, growing a U_GaN2 layer thereon, growing an NGaN layer and an LED full structure layer thereon; wherein the U_GaN1 layer includes a 3D1 layer grown at a low temperature and a low growth rate, growing a recrystallization layer thereon, and growing a 3D2 layer thereon; wherein the temperature of the recrystallization layer is higher than that of the 3D1 layer, the NH3 flow rate of the recrystallization layer is lower than that of the 3D1 layer, and the H2 flow rate is higher than that of the 3D1 layer.

[0007] Preferably, a 3D2R1 recrystallization layer and a 3D2R2 recrystallization layer are successively grown on the 3D1 layer. The two recrystallization layers can quickly pull the temperature to a high level for better recrystallization.

[0008] Preferably, the growth conditions of the 3D1 layer are as follows: temperature: 1030 - 1080 °C, NH3 flow rate: 15 - 80 SLM, N2 flow rate: 25 - 100 SLM, H2 flow rate: 120 - 350 SLM, TMG flow rate: 160 - 500 Sccm, growth thickness: 0.03 - 0.09 μm, pressure P = 200 Torr; rotation speed: 700 - 900 RPM.

[0009] Preferably, in the growth conditions of the 3D1 layer, the proportion of NH3 in the total gas is 8% - 15%, the proportion of N2 in the total gas is 15% - 30%, and the proportion of H2 is 50% - 80%.

[0010] Preferably, the growth conditions of the recrystallization layer are as follows: temperature: 1080 - 1100 °C, NH3 flow rate is less than that of the 3D1 layer, H2 flow rate is greater than that of the 3D1 layer, grow for 30 s - 3 min without Mo source introduced, pressure P = 200 Torr; rotation speed: 700 - 900 RPM, recrystallization time: 10 - 300 s.

[0011] Preferably, in the growth conditions of the recrystallization layer, the NH3 flow rate includes NH3 = 0.

[0012] Preferably, the growth time of the 3D2R1 recrystallization layer is 10 - 60 S, and the growth time of the 3D2R2 recrystallization layer is 1 - 3 min.

[0013] Preferably, the 3D2R1 - 3D2R2 layers are grown in the same conditions for 5 - 10 cycles, and the non - C - plane GaN is repeatedly recrystallized to improve the lattice quality.

[0014] Preferably, the growth conditions of the 3D2 layer are as follows: temperature: 1080 - 1100 °C, NH3 flow rate: 15 - 80 SLM, N2 flow rate: 25 - 100 SLM, H2 flow rate: 120 - 350 SLM, TMG flow rate: 400 - 1600 Sccm, grow for 5 - 12 min, pressure P = 200 Torr; rotation speed: 700 - 900 RPM, the growth atmosphere conditions of the 3D2 layer are the same as those of the 3D1 layer (higher temperature, faster growth rate).

[0015] Preferably, in the growth of the 3D2 layer, the proportion of NH3 in the total gas is 8% - 15%, the proportion of N2 in the total gas is 15% - 30%, and the proportion of H2 in the total gas is 50% - 80%.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The present invention innovatively utilizes the different atmospheres of the recrystallization layer to decompose GaN on the C-plane / non-C-plane, thereby eliminating the proportion of non-C-plane GaN crystals. On it, 3D2 with high temperature and high growth rate is grown, mainly GaN crystals on the C-plane, which is beneficial to eliminating dislocations in contact with the non-C-plane and reducing the generation of voids in the GaN crystals grown at the top of the patterned substrate, thereby improving the lattice quality of the epitaxial material and enhancing the light-emitting efficiency. Brief Description of the Drawings

[0018] Figure 1 It is a TEM image of a PSS patterned substrate and the actually grown U_GaN1 layer (3D layer) in the prior art.

[0019] Figure 2 It is a structural diagram of a high-light-efficiency light-emitting diode epitaxial wafer according to the present invention.

[0020] Figure 3 It is a recrystallization layer epitaxial structure diagram according to the present invention.

[0021] Figure 4 It is a demonstration process diagram according to the present invention.

[0022] Figure 5 It is a comparison diagram between the actually grown TEM image and the SEM image of the 3D layer according to the present invention.

[0023] Figure 6 It is an example diagram of Embodiment 2 according to the present invention.

[0024] Figure 7 It is a comparison diagram of the data of the epitaxial wafers grown by the new and old epitaxial structures. Detailed Embodiments

[0025] To further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following will, in conjunction with the accompanying drawings and preferred embodiments, describe in detail the specific embodiments, structures, features and their effects according to the present invention as follows.

[0026] As Figure 1 shown, in the actual growth process of the 3D by the existing growth method, a small amount of GaN crystals will also be generated on the non-polar surface of Al2O3, and will contact the GaN crystals grown on the C-plane at the top and below the substrate pattern, resulting in the following consequences: 1. Since the polarities of the two GaN are different, the atoms at the interface are not easy to bond, thus generating new dislocations or increasing the polarization effect at the interface due to the different polarities of GaN; 2. When the GaN crystals fill and cover the top of the substrate pattern, holes may be formed in the substrate pattern and its top region, thus affecting the light-emitting efficiency (see specifically Figure 1 in 1-1), Figure 1 in 1-2 is the TEM picture of the actually grown U_GaN1 layer (3D layer), which is basically consistent with the speculated growth.

[0027] AsFigure 2 As shown in the figure, the present invention provides a method for growing a high-light-efficiency light-emitting diode epitaxial wafer, including: a substrate, growing a buffer layer on the substrate, growing a U_GaN1 layer thereon, growing a U_GaN2 layer thereon, growing an NGaN layer and an LED full structure layer thereon; wherein the U_GaN1 layer includes a 3D1 layer grown at a low temperature and a low growth rate, growing a recrystallization layer thereon, and growing a 3D2 layer thereon; wherein the temperature of the recrystallization layer is higher than that of the 3D1 layer, the NH3 flow rate of the recrystallization layer is less than that of the 3D1 layer, and the H2 flow rate is greater than that of the 3D1 layer.

[0028] As Figure 3 shown, in order to quickly raise the temperature to a high level for better recrystallization, the recrystallization layer includes a 3D2R1 recrystallization layer and a 3D2R2 recrystallization layer. The 3D2R1 recrystallization layer is grown on the 3D1 layer, and the 3D2R2 recrystallization layer is grown on the 3D2R1 recrystallization layer. Among them, the NH3 flow rate of the 3D2R1 / 2 pause layer is less than that of the 3D1 layer, the H2 flow rate of the 3D2R1 / 2 pause layer is greater than that of the 3D1 layer, the temperature of the 3D2R1 / 2 is 30 - 50 degrees higher than that of the 3D1 layer, and the growth thickness of the 3D1 layer is 0.03 - 0.09 μm. 3D1 - 3D2R2 are grown by cycling, and non-C-plane-grown GaN is repeatedly cracked and recrystallized to reduce the proportion of non-C-plane GaN and improve the lattice quality of the overall epitaxial layer.

[0029] The process of dislocation / stress generation and improvement at the contact surface between GaN crystals on the non-C plane and GaN crystals grown on the C plane through the epitaxial structure of the recrystallization layer:

[0030] Since the GaN grown on the buffer layer grows on the C plane, the C plane has strong polarity and there are GaN nuclei conducive to crystallization. The growth rate of GaN on the C plane is fast and the proportion is high. Due to the weak polarity of the non-C plane, the generated GaN has a slow growth rate and a low proportion. Moreover, due to the different polarities of GaN formed by the two epitaxial methods, there are problems such as difficult bonding and large polarization effects, which affect the lattice quality. The present invention uses different atmospheres in the recrystallization layer to decompose GaN on the C plane / non-C plane, thereby eliminating the proportion of non-C plane GaN crystals. The 3D2 grown thereon has a high temperature and a high growth rate, mainly GaN crystals on the C plane, which is conducive to eliminating dislocations in contact with the non-C plane and reducing the generation of voids in the GaN crystals grown at the top of the patterned substrate, thereby improving the lattice quality of the epitaxial material and enhancing the light emission efficiency. The demonstration process is shown in Figure 4 , and the comparison of the actual growth TEM image and the 3D layer SEM image under this condition is as Figure 5 , which is basically consistent with the speculation.

[0031] The growth conditions of the U_GaN1 layer are:

[0032] Example 1:

[0033] Growth conditions of 3D1 layer: Temp: 1030 - 1080 °C, NH3 flow rate: 15 - 80 SLM (the proportion of NH3 in the total gas is 8% - 15%), N2 flow rate: 25 - 100 SLM (the proportion of N2 in the total gas is 15% - 30%), H2: 120 - 350 SLM (the proportion of H2 in the total gas is 50% - 80%), TMG flow rate: 160 - 500 Sccm, growth thickness is 0.03 - 0.09 μm, pressure P = 200 Torr; rotation speed: 700 - 900 RPM.

[0034] Growth conditions of 3D2R1 / 2 recrystallization layer: Temp: 1080 - 1100 °C, NH3 flow rate is less than that of 3D1 (including NH3 = 0), H2 flow rate is greater than that of 3D1, grow for 30 s - 3 min without Mo source input, pressure P = 200 Torr; rotation speed: 700 - 900 RPM, recrystallization time is 10 - 300 s.

[0035] Growth conditions of 3D2 layer: Temp: 1080 - 1100 °C, NH3 flow rate: 15 - 80 SLM (the proportion of NH3 in the total gas is 8% - 15%), N2: 25 - 100 SLM (the proportion of N2 in the total gas is 15% - 30%), H2 flow rate: 120 - 350 SLM (the proportion of H2 in the total gas is 50% - 80%), TMG flow rate: 400 - 1600 Sccm, grow for 5 - 12 min, pressure P = 200 Torr; rotation speed: 700 - 900 RPM, the growth atmosphere conditions of 3D2 layer are the same as those of 3D1 layer (higher temperature, faster growth rate).

[0036] Grow the 3D1 - 3D2R layer under the same conditions for 5 - loop times, and repeatedly recrystallize the non - C - plane GaN to improve the lattice quality.

[0037] Example 2:

[0038] Growth conditions of 3D1 layer: Temp: 1030 °C, NH3 flow rate: 15 - 80 SLM (the proportion of NH3 in the total gas is 8% - 15%), N2 flow rate: 25 - 100 SLM (the proportion of N2 in the total gas is 15% - 30%), H2 flow rate: 120 - 350 SLM (the proportion of H2 in the total gas is 50% - 80%), TMG flow rate: 160 - 500 Sccm, growth thickness is 0.03 - 0.09 μm, pressure P = 200 Torr; rotation speed: 700 - 900 RPM; the temperature of each cycle of 3D1 layer is 5 - 10 higher than that of the previous cycle (Temp: 1035 - 1070 °C), until the temperature of the last cycle is 1080 °C.

[0039] Growth conditions of the 3D2R1 / 2 recrystallization layer: Temp: 1080 - 1100 °C, NH3 flow rate is A (where A < 3D1 NH3 flow rate), H2 flow rate is B (where B > 3D1 H2 flow rate). Grow for 30 s - 3 min under the condition of no Mo source introduced, pressure P = 200 Torr; rotation speed: 700 - 900 RPM, recrystallization time 10 - 300 s, where the growth temperature of each cycle is different from the previous cycle (the temperature of the recrystallization layer is 30 - 50 °C higher than that of the 3D1 layer); the gas volume introduced in each cycle is different from the previous cycle (the NH3 flow rate introduced in the recrystallization layer is less than 3D1, the H2 flow rate introduced is greater than 3D1, including NH3 = 0 in one or more cycles).

[0040] Growth conditions of the 3D2 layer: Temp: 1080 - 1100 °C, NH3 flow rate: 15 - 80 SLM (the proportion of NH3 in the total gas is 8% - 15%), N2 flow rate: 25 - 100 SLM (the proportion of N2 in the total gas is 15% - 30%), H2 flow rate: 120 - 350 SLM (the proportion of H2 in the total gas is 50% - 80%), TMG flow rate: 400 - 1600 Sccm, grow for 5 - 12 min, pressure P = 200 Torr; rotation speed: 700 - 900 RPM, the growth atmosphere conditions of 3D2 are the same as those of 3D1 (higher temperature, faster growth rate).

[0041] The 3D1 - 3D2R layers are grown in cycles 5 - 10 times. Among them, the temperature of the 3D1 layer is 5 °C higher than the previous cycle in each cycle, and the temperature of the recrystallization layer in each cycle... Taking 3 cycles as an example, see Figure 6 。

[0042] In this invention, for the epitaxial wafers grown with the same substrate, on the same machine, and with new and old epitaxial structures, through PL data testing, it shows that the XRD data of 002 / 102 of the new structure becomes significantly smaller, indicating that the lattice quality of the new structure grown is better, thus achieving the purpose of ultimately improving the light efficiency. For specific data, see Figure 7 。

[0043] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Although the present invention has been disclosed as above with the preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art, without departing from the scope of the technical solution of the present invention, may make some changes or modifications to the above - disclosed technical content to obtain equivalent embodiments with equivalent changes. However, as long as it does not depart from the content of the technical solution of the present invention, any brief modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for growing a high-efficiency light-emitting diode epitaxial wafer, characterized in that: The invention comprises: a substrate, a buffer layer is grown on the substrate, a U_GaN1 layer is grown on the substrate, a U_GaN2 layer is grown on the substrate, an NGaN layer and an LED full structure layer are grown on the substrate; wherein the U_GaN1 layer comprises a 3D1 layer grown at a low temperature and a low growth rate, a recrystallization layer is grown on the substrate, and a 3D2 layer is grown on the substrate; wherein the temperature of the recrystallization layer is greater than that of the 3D1 layer, the NH3 flow rate of the recrystallization layer is less than that of the 3D1 layer, and the H2 flow rate is greater than that of the 3D1 layer; the growth conditions of the 3D1 layer are as follows: temperature: 1030-1080 degrees, NH3 flow rate: 15-80 SLM, N2 flow rate: 25-100 SLM, H2 flow rate: 120-350 SLM, TMG flow rate: 160-500 Sccm, growth thickness is 0.03-0.09 μm, and pressure P=200 Torr; Rotation speed: 700~900RPM; the recrystallization layer growth conditions are: temperature: 1080~1100 degrees, growth time of 30s~3 min without Mo source, pressure P=200 Torr; Rotation speed: 700~900RPM, recrystallization time 10~300s; the 3D2 layer growth conditions are temperature: 1080~1100 degrees, NH3 flow: 15~80SLM, N2 flow: 25~100SLM, H2 flow: 120~350 SLM, TMG flow: 400~1600 Sccm, growth 5~12min, pressure P=200 Torr; Rotation speed: 700~900RPM. The gas atmosphere conditions involved in the growth of the 3D2 layer are the same as those of the 3D1 layer.

2. A method for growing a high-efficiency light-emitting diode epitaxial wafer as claimed in claim 1, characterized in that: In the 3D1 layer growth conditions, NH3 accounts for 8% to 15% of the total gas, N2 accounts for 15% to 30% of the total gas, and H2 accounts for 50% to 80% of the total gas.

3. The method for growing a high-efficiency light-emitting diode epitaxial wafer according to claim 1, characterized in that: The NH3 flow rate in the recrystallization layer growth conditions includes NH3=0.

4. The method for growing a high-efficiency light-emitting diode epitaxial wafer according to claim 1, characterized in that: A 3D2R1 recrystallized layer and a 3D2R2 recrystallized layer are sequentially grown on the 3D1 layer.

5. A method for growing a high-efficiency light-emitting diode epitaxial wafer as claimed in claim 4, characterized in that: The growth time of the 3D2R1 recrystallization layer is 10-60 seconds, and the growth time of the 3D2R2 recrystallization layer is 1-3 minutes.

6. A method for growing a high-efficiency light-emitting diode epitaxial wafer as claimed in claim 5, characterized in that: The 3D2R1-3D2R2 layers are cyclically grown for 5-10 times under the same conditions, and the non-C-face GaN is repeatedly recrystallized to improve the lattice quality.

7. The method for growing a high-efficiency light-emitting diode epitaxial wafer according to claim 1, characterized in that: During the growth of the 3D2 layer, NH3 accounts for 8%~15% of the total gas, N2 accounts for 15%~30% of the total gas, and H2 accounts for 50%~80% of the total gas.

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