Growth method of green light LED epitaxial structure

Abstract

The invention is applicable to the technical field of LED (light-emitting diode) preparation, and provides a growth method of a green-light LED epitaxial structure, which comprises the following steps of: sequentially growing a nucleating layer, a U-shaped high-temperature GaN layer which is not doped, an N-shaped high-temperature GaN layer which is continuously doped with Si, a multi-quantum well light-emitting layer, a P-shaped AlGaN layer which is doped with Al and Mg and a high-temperature P-shaped GaN layer which is doped with Mg by adopting an MOCVD (metal organic chemical vapor deposition) process; the composite nucleating layer replaces a traditional single GaN nucleating layer, lattice mismatch and stress accumulation are reduced from the source, and the dislocation defect of the multi-quantum well layer is reduced; according to the invention, electric leakage of a green light LED device is effectively reduced, the luminous efficiency and the antistatic capability are improved, and the method is suitable for preparation of a high-brightness GaN-based green light LED epitaxial wafer.

Description

Technical Field

[0001] This invention relates to the field of LED fabrication technology, specifically a method for growing a green LED epitaxial structure. Background Technology

[0002] Currently, the emitting layer of most GaN-based green LEDs in China uses a multi-quantum-well layer formed by an InGaN / GaN superlattice. Because the growth temperature of the green quantum well region is lower than that of the blue quantum well, the crystal quality is poor, resulting in numerous dislocation defects. This leads to high leakage current and low luminous efficiency in the LED device, and green LEDs are more sensitive to defects. Traditional green LED epitaxial growth uses a single GaN nucleation layer, which results in severe lattice mismatch and stress accumulation, making it difficult to fundamentally solve the defect problem.

[0003] Therefore, in view of the above situation, there is an urgent need to provide a growth method for green LED epitaxial structures to overcome the shortcomings in current practical applications. Summary of the Invention

[0004] The purpose of this invention is to provide a method for growing a green LED epitaxial structure, which effectively solves the problems mentioned in the background art.

[0005] This invention is implemented as follows: a method for growing a green LED epitaxial structure using MOCVD technology, specifically including the following steps: S1. Anneal the sapphire substrate in a hydrogen atmosphere at a temperature of 1000-1020℃, a pressure of 100-150mbar, and a treatment time of 5-10 minutes. S2. Cool down to 750-850℃, control the pressure at 100-500mbar, and grow a nucleation layer on the sapphire substrate. S3. Heat to 1030-1080℃ and keep the temperature constant, control the pressure at 150-500mbar, and continue to grow an undoped U-shaped high-temperature GaN layer of 2-4µm. S4. Keep the temperature constant and control the pressure at 150-500 mbar, then grow 1-2 μm of continuously doped Si N-type high-temperature GaN. S5. Cool to 690-740℃, control pressure at 200-400mbar, and periodically grow In from 2.0-3.0nm. x Ga （1-x） A multi-quantum-well light-emitting layer consisting of an N (x=0.18-0.23) well layer and a 10-15 nm GaN barrier layer; S6. Heat to 850-950℃, control the pressure at 100-300mbar, and use TMGa, TMAl and CP2Mg as MO sources to continuously grow 20-100nm of Al and Mg-doped P-type AlGaN layers. S7. Heat to 900-950℃, control the pressure at 200-300mbar, use TMGa and CP2Mg as MO sources, and grow 50-200nm Mg-doped high-temperature P-type GaN layers. S8. Cool down to 750-800℃, control the pressure at 500-800mbar, anneal in the furnace for 25-30 minutes, and then cool down in the furnace.

[0006] As a further aspect of the present invention: in S2, the nucleation layer growth step is as follows: S2.1, Grow an ALN ​​layer with a thickness of 1-3 nm; S2.2. Grow an AlGaN layer with a thickness of 2-5 nm on the ALN layer, with the Al composition gradually decreasing. S2.3. Grow an InGaN layer with a thickness of 2-5 nm on the AlGaN layer; S2.4. Grow a GaN layer with a thickness of 5-10 nm on the InGaN layer; The MO sources used are TMGa, TMIn and TMAl, with TMGa used at a concentration of 40-100 sccm, TMIn used at a concentration of 100-500 sccm, and TMAl used at a concentration of 50-200 sccm.

[0007] As a further aspect of the present invention: in S3, the MO source used is TMGa, and the amount of TMGa used is 200-800 sccm.

[0008] As a further aspect of the present invention: in S4, the MO source used is TMGa, and the amount of TMGa used is 600-1000 sccm.

[0009] As a further aspect of the present invention: in S4, the Si doping concentration is 8E+18-2E+19 atom / cm². 3 .

[0010] As a further aspect of the present invention: in S5, the number of cycles is 6-15, the overall thickness of the multi-quantum-well light-emitting layer is controlled at 120-300nm, and the MO source used is TEGa and TMIn, with TEGa amounting to 200-1000sccm and TMIn amounting to 200-2000sccm.

[0011] As a further aspect of the present invention: in S6, the MO source used is TMGa, TMAl and CP2Mg, the amount of TMGa is 40-200 sccm, the amount of TMAl is 20-200 sccm and the amount of CP2Mg is 100-1000 sccm.

[0012] As a further aspect of the present invention: in S6, the doping concentration of Mg is 3E+18-6E+18 atom / cm³. 3 The Al doping concentration is 1E+20-3E+20 atom / cm³ 3 .

[0013] As a further aspect of the present invention: in S7, the MO source used is TMGa and CP2Mg, the amount of TMGa is 40-200 sccm, and the amount of CP2Mg is 200-2000 sccm.

[0014] As a further aspect of the present invention: in S7, the doping concentration of Mg is 1E+19-3E+19 atom / cm³. 3 .

[0015] Compared with existing technologies, the beneficial effects of this invention are as follows: By first growing an AlN layer, the stress at the contact surface with the sapphire substrate is reduced. Then, a GaN layer with a gradually decreasing Al composition is grown, allowing the lattice to slowly transition to GaN. Next, an InGaN layer is grown, which can partially compensate for the tensile stress in subsequent growth layers, reducing overall lattice mismatch and stress accumulation from the source. Finally, GaN is grown to cover the InGaN layer, reducing the decomposition of In in the InGaN layer and ensuring lattice matching with the subsequently grown GaN layer. The growth of this nucleation layer significantly reduces leakage current and improves luminous efficiency in green LEDs. Attached Figure Description

[0016] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of a traditional LED epitaxial structure.

[0018] Figure 2 This is a schematic diagram of the green LED epitaxial structure provided by the present invention.

[0019] Figure 3 This is a schematic diagram of the brightness test results of Sample 1 and Sample 2 in Example 1.

[0020] Figure 4 This is a schematic diagram of the antistatic ability test results for samples 1 and 2 in Example 1.

[0021] In the attached diagram: 1 - P-type GaN layer, 2 - P-type AlGaN layer, 3.1 - GaN barrier layer, 3.2 - In x Ga （1-x） N (x=0.20-0.22) well layer, 4-N-type high-temperature GaN, 5-U-type high-temperature GaN layer, 6.1-GaN layer, 6.2-InGaN layer, 6.3-AlGaN layer, 6.4-ALN layer, 7-substrate sapphire substrate. Detailed Implementation

[0022] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] The present invention will be further explained below with reference to specific embodiments.

[0024] This invention utilizes MOCVD to grow high-brightness GaN-based LED epitaxial wafers. High-purity H2, high-purity N2, or a mixture of both are used as the carrier gas. High-purity NH3 is used as the N source, trimethylgallium (TMGa) as the gallium source, trimethylindium (TMIn) as the indium source, silane (SiH4) as the N-type dopant, trimethylaluminum (TMAl) as the aluminum source, and magnesium pyrocene (CP2Mg) as the P-type dopant. The substrate is (0001)-plane sapphire, and the reaction chamber pressure is between 150 mbar and 600 mbar.

[0025] Please see Figures 2-4 The present invention provides a method for growing a green LED epitaxial structure, the specific steps of which include: S1. Anneal the sapphire substrate 7 in a hydrogen atmosphere at a temperature of 1000-1020℃, a pressure of 100-150mbar, and a treatment time of 5-10 minutes. S2. Cool to 750-850℃, control the pressure at 100-500mbar, and grow a nucleation layer on the sapphire substrate 7; the nucleation layer growth steps are as follows: S2.1, Grow an ALN ​​layer with a thickness of 1-3 nm 6.4; S2.2, An AlGaN layer 6.3 with a thickness of 2-5 nm is grown on the AlN layer 6.4, with the Al composition gradually decreasing; S2.3, Grow an InGaN layer 6.2 with a thickness of 2-5 nm on the AlGaN layer 6.3; S2.4, Grow a GaN layer 6.1 with a thickness of 5-10 nm on the InGaN layer 6.2; The MO sources used are TMGa, TMIn and TMAl, with TMGa used at a concentration of 40-100 sccm, TMIn used at a concentration of 100-500 sccm, and TMAl used at a concentration of 50-200 sccm.

[0026] S3. Heat to 1030-1080℃ and keep the temperature constant, control the pressure at 150-500mbar, and continue to grow an undoped U-shaped high-temperature GaN layer of 2-4um; the MO source used is TMGa, and the amount of TMGa is 200-800sccm.

[0027] S4. Maintaining a constant temperature and pressure of 150-500 mbar, grow 1-2 μm thick, continuously doped Si-based N-type high-temperature GaN4. The MO source used is TMGa, with a TMGa concentration of 600-1000 sccm, and the Si doping concentration is 8E+18-2E+19 atom / cm. 3 .

[0028] S5. Cool to 690-740℃, control pressure at 200-400mbar, and periodically grow In from 2.0-3.0nm. x Ga （1-x） The light-emitting layer consists of an N (x=0.18-0.23) well layer 3.2 and a 10-15 nm GaN barrier layer 3.1; the number of periods is 6-15, and the overall thickness of the light-emitting layer is controlled at 120-300 nm. The MO source used is TEGa and TMIn, with TEGa amounting to 200-1000 sccm and TMIn amounting to 200-2000 sccm.

[0029] S6. Heat to 850-950℃, control the pressure at 100-300mbar, and use TMGa, TMAl, and CP2Mg as MO sources to continuously grow 20-100nm Al- and Mg-doped P-type AlGaN layers. The MO sources used are TMGa, TMAl, and CP2Mg, with TMGa dosage at 40-200 sccm, TMAl dosage at 20-200 sccm, and CP2Mg dosage at 100-1000 sccm. The Mg doping concentration is 3E+18-6E+18 atom / cm. 3 The Al doping concentration is 1E+20-3E+20 atom / cm³ 3 .

[0030] S7. The temperature is increased to 900-950℃, and the pressure is controlled at 200-300 mbar. The MO source used is TMGa and CP2Mg to grow a 50-200 nm Mg-doped high-temperature p-type GaN layer 1. The MO source used is TMGa and CP2Mg, with TMGa dosage at 40-200 sccm and CP2Mg dosage at 200-2000 sccm. In S7, the Mg doping concentration is 1E+19-3E+19 atom / cm. 3。

[0031] S8. Cool down to 750-800℃, control the pressure at 500-800mbar, anneal in the furnace for 25-30 minutes, and then cool down in the furnace.

[0032] In this embodiment, by first growing an AlN layer to reduce the stress at the contact surface with the sapphire substrate, followed by growing a GaN layer with a gradually decreasing Al composition, the lattice gradually transitions to GaN. Then, an InGaN layer is grown, which partially compensates for the tensile stress in the subsequent growth layers, reducing overall lattice mismatch and stress accumulation from the source. Finally, GaN is grown to cover the InGaN layer, reducing the decomposition of In in the InGaN layer and ensuring lattice matching with the subsequently grown GaN layer. This nucleation layer growth significantly reduces leakage current and improves luminous efficiency in green LEDs.

[0033] Example 1: Sample 1 was prepared according to conventional LED growth methods, and Sample 2 was prepared according to the method described in this invention. Samples 1 and 2 were deposited with an ITO layer of 300-700 Å under the same pre-process conditions, a Cr / Pt / Au electrode of 400-500 Å under the same conditions, and a protective SiO2 layer of 100-200 Å under the same conditions. Then, the samples were ground and cut into 16.5 μm * 16.5 mil chip particles under the same conditions. 150 chips were selected from the same locations for both Samples 1 and 2, and they were packaged into green LEDs using the same packaging process. The photoelectric performance of Samples 1 and 2 was then tested using an integrating sphere at a driving current of 150 mA. The obtained parameters are shown in [details omitted]. Figure 3 and Figure 4 ; Please analyze and compare the obtained data, and refer to Table 1 and the appendix. Figure 3 As shown in Table 1, the XRD test results indicate that the full width at half maximum (FWHM) of the 102 and 002 peaks in the GaN grown according to this invention are smaller than those grown using traditional methods, demonstrating a significant improvement in the crystal quality of the GaN grown according to this invention. Figure 3 The data shows that sample 2 has a significantly higher brightness than sample 2; from Figure 4The data shows that the ESD yield of sample 2 increased significantly from 2kvs to 8kv compared to sample 1, indicating a substantial increase in ESD pass rate. The growth method provided by this invention improves the crystal quality of large-size chips, enhances ESD resistance, and also increases the light output power of LEDs to some extent.

[0034] Table 1 XRD characterization

[0035] In summary, the growth method provided by this invention can effectively reduce dislocation defects in the multi-quantum-well layer of green LEDs from the source, thereby improving the light output power of green LEDs to a certain extent. By using an AlN / Al-doped graded GaN layer / InGaN / GaN nucleation layer to replace the traditional GaN nucleation layer, the overall lattice mismatch and stress accumulation are reduced from the source, thereby reducing defect generation.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for growing a green LED epitaxial structure, characterized in that, The MOCVD process is adopted, and the specific steps include: S1, annealing the substrate sapphire substrate (7) in a hydrogen atmosphere, the annealing temperature is 1000-1020℃, the pressure is controlled at 100-150mbar, and the processing time is 5-10 minutes; S2, cooling to 750-850℃, the pressure is controlled at 100-500mbar, and a nucleation layer is grown on the substrate sapphire substrate (7); S3, heating to 1030-1080℃, keeping the temperature unchanged, the pressure is controlled at 150-500mbar, and a 2-4um undoped U-shaped high-temperature GaN layer (5) is continuously grown; S4, keeping the temperature unchanged, the pressure is controlled at 150-500mbar, and then a 1-2um continuously doped Si N-type high-temperature GaN (4) is grown; S5, cooling to 690-740 °C, pressure control at 200-400 mbar, periodic growth by 2.0-3.0 nm of In x Ga （1-x） N (x = 0.18-0.23) well layer (3.2) and 10-15 nm of GaN barrier layer (3.1) consisting of multiple quantum well light emitting layer; S6, heating to 850-950℃, the pressure is controlled at 100-300mbar, the MO source used is TMGa, TMAl and CP2Mg, and a 20-100nm P-type AlGaN layer (2) doped with Al and Mg is continuously grown; S7, heating to 900-950℃, the pressure is controlled at 200-300mbar, the MO source used is TMGa and CP2Mg, and a 50-200nm high-temperature P-type GaN layer (1) doped with Mg is grown; S8, cooling to 750-800℃, the pressure is controlled at 500-800mbar, and after annealing in the furnace for 25-30min, the furnace is cooled.

2. The method of claim 1, wherein the green LED epitaxial structure is grown by metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE). In S2, the nucleation layer growth step is: S2.1, growing a layer of ALN layer (6.4) with a thickness of 1-3nm; S2.2, growing a layer of AlGaN layer (6.3) with a thickness of 2-5nm on the ALN layer (6.4), and the Al component gradually decreases; S2.3, growing a layer of InGaN layer (6.2) with a thickness of 2-5nm on the AlGaN layer (6.3); S2.4, growing a layer of GaN layer (6.1) with a thickness of 5-10nm on the InGaN layer (6.2); The MO source used is TMGa, TMIn and TMAl, the amount of TMGa is 40-100sccm, the amount of TMIn is 100-500sccm, and the amount of TMAl is 50-200sccm.

3. The method of claim 1, wherein the green LED epitaxial structure is grown by metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE). In S3, the MO source used is TMGa, and the amount of TMGa is 200-800sccm.

4. The method of claim 1, wherein the green LED epitaxial structure is grown by metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE). In S4, the MO source used is TMGa, and the amount of TMGa is 600-1000sccm.

5. The method of claim 1, wherein the green LED epitaxial structure is grown by metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE). In S4, the doping concentration of Si is 8E+18-2E+19 atom / cm 3 .

6. The method of claim 1, wherein the green LED epitaxial structure is grown by metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE). In S5, the number of cycles is 6-15, the total thickness of the multi-quantum well light emitting layer is controlled at 120-300nm, the MO source used is TEGa and TMIn, the amount of TEGa is 200-1000sccm, and the amount of TMIn is 200-2000sccm.

7. The method of claim 6, wherein the green LED epitaxial structure is grown by metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE). In S6, the MO source used is TMGa, TMAl and CP2Mg, the amount of TMGa is 40-200sccm, the amount of TMAl is 20-200sccm, and the amount of CP2Mg is 100-1000sccm.

8. The method of claim 6, wherein the green LED epitaxial structure is grown by metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE). In S6, the doping concentration of Mg is 3E+18-6E+18 atom / cm 3 , and the doping concentration of Al is 1E+20-3E+20 atom / cm 3 .

9. The method of claim 1, wherein the green LED epitaxial structure is grown by metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE). In S7, the MO source used is TMGa and CP2Mg, the amount of TMGa used is 40-200 sccm, and the amount of CP2Mg used is 200-2000 sccm.

10. The method of claim 1, wherein the green LED epitaxial structure is grown by metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE). In S7, the doping concentration of Mg is 1E+19-3E+19 atom / cm 3 .

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