GaN-based LED based on high In component thermal decomposition superlattice layer

Abstract

The invention discloses a GaN-based LED based on a high In component thermal decomposition superlattice layer. A u-GaN layer, an n-GaN layer, the high In component thermal decomposition superlattice layer, a medium-temperature GaN repairing layer, a high-temperature GaN decomposition layer, a quantum well layer, a p-GaN layer and a p +-GaN layer are sequentially deposited on a sapphire substrate from bottom to top. Wherein the high In component thermal decomposition superlattice layer comprises 2-5 groups of InGaN decomposition layers and GaN cap layers which are sequentially and circularly stacked. According to the device structure, stress is fully released, the In component content of the quantum well region is improved, emission of higher wavelength is achieved, and the external quantum efficiency is kept.

Description

Technical Field

[0001] The present invention relates to the technical field of light-emitting diodes, and particularly to a GaN-based LED based on a high In-component thermally decomposed superlattice layer. Background Art

[0002] The third-generation semiconductor materials represented by GaN have received wide attention. They have a wide bandgap, a high electron saturation rate, a high breakdown field strength, and a high thermal conductivity, and are widely used in the fields of semiconductor lighting, 5G communication, microwave radio frequency, etc. With the breakthrough of key technologies such as p-type doping and quantum well preparation, GaN-based optoelectronic devices have made great progress. When the emission wavelength of InGaN-based LEDs extends from blue light to green light, the efficiency drops by more than 50%, and this phenomenon is called the "green gap", which restricts the realization of high-efficiency long-wavelength GaN-based LEDs.

[0003] The emission of long wavelengths requires a higher In component to be incorporated. Usually, the growth temperature of quantum wells with a high In component is relatively low, resulting in poor crystal quality and interface characteristics of the quantum wells, seriously affecting the external quantum efficiency of the devices. Moreover, as the In component increases, the lattice mismatch between the InGaN well layer and the underlying GaN increases, and the compressive strain in the quantum well gradually strengthens. On the one hand, the stronger compressive strain leads to a decrease in crystal quality and reduces the external quantum efficiency of the chip. On the other hand, the compressive strain will cause piezoelectric polarization, and the polarization electric field makes the energy band of the semiconductor tilt, reducing the overlap degree of the electron-hole wave functions, resulting in the shift of the emission wavelength and the reduction of the external quantum efficiency of the LED device. Usually, the metalorganic chemical vapor deposition (MOCVD) technology is used to introduce an InGaN / GaN superlattice layer to relieve the stress in the quantum well active region, reduce the density of V-shaped pits in the quantum well, improve the current diffusion in the LED, and thus improve the external quantum efficiency and luminous efficiency of the LED.

[0004] Although some progress has been made in the research of superlattice LEDs, there are still the following deficiencies:

[0005] 1. The stress release of the existing superlattice structure is insufficient: The crystal axis length ratios of group III nitride materials are all smaller than the unit cell of the perfect hexagonal structure, making the positive and negative charge centers in the unit cell unable to coincide, generating a piezoelectric polarization effect. The energy band of the InGaN / GaN quantum well in the polarization electric field will tilt, causing electrons and holes to be confined on both sides of the quantum well, resulting in a weakening of the overlap degree of the electron-hole wave functions, reducing the recombination probability, and causing a sharp drop in the external quantum efficiency of the LED. The existing superlattice structure has insufficient stress release, and the lattice mismatch between the quantum well region and the underlying GaN is still very large.

[0006] 2. Short emission wavelength: Due to the compositional migration effect, during the growth of InGaN thin films, as the film thickness increases, the crystal quality deteriorates, generating a large number of crystal defects. At the same time, due to the increase in lattice mismatch, this effect is exacerbated, making it impossible for the In component to be effectively incorporated, resulting in a short emission wavelength.

[0007] 3. Low efficiency of LEDs realized by traditional superlattices: The cracking rate of the N source (NH 3 ) of the superlattice grown at low temperature is low, resulting in the appearance of N vacancies in the crystal, deteriorating the crystal quality. Moreover, the quantum wells with high In content cause a greater lattice mismatch and are accompanied by a dislocation density of a higher order of magnitude, both of which reduce the device efficiency.

[0008] 4. The common stress relaxation template (SRT) prepares a porous GaN pseudosubstrate by using electrochemical etching technology and adjusts the relaxation of the InGaN template on the GaN pseudosubstrate through different porosities. This SRT requires a complex manufacturing process.

[0009] 5. The existing high-temperature repair layer has a significant negative impact on the crystal quality and surface morphology, ultimately reducing the performance of the LED. Summary of the Invention

[0010] To solve the above technical problems, the present invention provides a GaN-based LED based on a high-In-composition thermally decomposed superlattice layer. The decomposition of InGaN in the high-In-composition thermally decomposed superlattice layer generates voids to release stress through a high-temperature GaN decomposition layer, and at the same time, a medium-temperature GaN repair layer is used to restore the quality damage caused by the decomposition.

[0011] To solve the above problems, the present invention adopts the following technical solutions.

[0012] The GaN-based LED based on a high-In-composition thermally decomposed superlattice layer is characterized in that a u-GaN layer (i.e., an undoped GaN layer), an n-GaN layer (i.e., an n-type doped GaN layer), a high-In-composition thermally decomposed superlattice layer, a medium-temperature GaN repair layer, a high-temperature GaN decomposition layer, a quantum well layer, and a p-GaN layer (i.e., a p-type doped GaN layer), p + -GaN layer (i.e., a p-type heavily doped GaN layer) are sequentially deposited from bottom to top on a sapphire substrate; the high-In-composition thermally decomposed superlattice layer includes 2 to 5 groups of InGaN decomposition layers and GaN cap layers (one InGaN decomposition layer and one GaN cap layer form a group) stacked in sequence and cyclically.

[0013] Furthermore, the growth temperature of the u-GaN layer is 1050 - 1150 °C, and the growth thickness is 2 - 4 μm.

[0014] Further, the growth temperature of the n-GaN layer is 1000 - 1200 °C, the growth thickness is 2 - 5 μm, Si doping is adopted, and the doping concentration is 1×10 19 ~1.5×10 19 cm -3 。

[0015] Further, in the high In-component thermally decomposed superlattice layer: the In molar percentage of the InGaN decomposition layer is 25 - 30%; the growth temperature of the InGaN decomposition layer and the GaN cap layer is 700 - 750 °C, and the growth pressure is 180 - 250 torr; the thickness of the InGaN decomposition layer is 2 - 2.5 nm, and the thickness of the GaN cap layer is 3 - 4 nm.

[0016] Further, in the high In-component thermally decomposed superlattice layer: the V / III ratio for the growth of the InGaN decomposition layer is 1000 - 1200, and the V / III ratio for the growth of the GaN cap layer is 2600 - 2800.

[0017] Further, the growth temperature of the medium-temperature GaN repair layer is 850 - 870 °C, the growth pressure is 150 - 200 torr, the V / III ratio for growth is 1100 - 1250, and the thickness is 110 - 130 nm.

[0018] Further, the growth temperature of the high-temperature GaN decomposition layer is 970 - 1050 °C, the growth pressure is 150 - 200 torr, the V / III ratio for growth is 500 - 600, and the thickness is 20 - 30 nm.

[0019] Further, on the quantum well layer, from bottom to top, there are successively an In 0.2 Ga 0.8 N well layer with a thickness of 3 nm, a GaN barrier layer with a thickness of 9 nm, an In 0.3 Ga 0.7 N well layer with a thickness of 3 nm, an Al 0.1 Ga 0.9 N barrier layer with a thickness of 6 nm, an In 0.3 Ga 0.7 N well layer with a thickness of 3 nm, and an Al 0.1 Ga 0.9 N barrier layer with a thickness of 6 nm. Among them, the growth temperature of the In 0.2 Ga 0.8 N well layer and the GaN barrier layer is 765 °C, and the growth temperature of the In 0.3 Ga 0.7 N well layer and the Al 0.1 Ga 0.9 N barrier layer is 720 °C.

[0020] Furthermore, the thickness of the p-GaN layer is 70 - 90 nm, the growth temperature is 950 - 1000 °C, Mg doping is used, and the doping concentration is 2×10 20 ~2.5×10 20 cm -3 ; the thickness of the p + -GaN layer is 2 - 5 nm, the growth temperature is 860 - 885 °C, Mg doping is used, and the doping concentration is 4×10 21 ~5×10 21 cm -3 .

[0021] A preparation method of a GaN-based LED based on a high In-component thermally decomposed superlattice layer includes the following steps:

[0022] S1. At a temperature of 950 - 1100 °C, perform a reduction treatment on the patterned sapphire substrate in an H 2 atmosphere for 200 - 400 s to remove surface impurities and oxides;

[0023] S2. Grow a u-GaN layer on the surface of the sapphire substrate: Use trimethylgallium as the gallium source, NH 3 as the nitrogen source, H 2 as the carrier gas, control the growth temperature to be 1050 - 1150 °C, the growth time to be 3000 - 3500 s, the growth pressure to be 400 torr, and the V / III ratio to be 1000 - 1200;

[0024] S3. Grow an n-GaN layer on the surface of the u-GaN layer: Use trimethylgallium as the gallium source, NH 3 as the nitrogen source, SiH 4 as the silicon source, H 2 as the carrier gas, control the growth temperature to be 1000 - 1200 °C, the growth time to be 1500 - 1800 s, the growth pressure to be 400 torr, and the V / III ratio to be 600 - 800;

[0025] S4. Sequentially and cyclically grow an InGaN decomposition layer and a GaN cap layer on the surface of the n-GaN layer:

[0026] InGaN decomposition layer: Use triethylgallium as the gallium source, trimethylindium as the indium source, NH 3 as the nitrogen source, N 2 as the carrier gas, control the growth temperature to be 700 - 750 °C, the growth time to be 100 - 200 s, the growth pressure to be 180 - 250 torr, and the V / III ratio to be 1000 - 1200;

[0027] GaN cap layer: Use trimethylgallium as the gallium source, NH 3 as the nitrogen source, N 2Using [gas name] as the carrier gas, control the growth temperature to be 700 - 750 °C, the growth time to be 200 - 300 s, the growth pressure to be 180 - 250 torr, and the V / III ratio to be 2600 - 2800;

[0028] S5, grow a medium-temperature GaN repair layer on the surface of the high In-component thermally decomposed superlattice layer: Use trimethylgallium as the gallium source, NH 3 as the nitrogen source, N 2 as the carrier gas, control the growth temperature to be 850 - 870 °C, the growth time to be 300 - 400 s, the growth pressure to be 150 - 200 torr, and the V / III ratio to be 1100 - 1250;

[0029] S6, grow a high-temperature GaN decomposition layer on the surface of the medium-temperature GaN repair layer: Use trimethylgallium as the gallium source, NH 3 as the nitrogen source, N 2 as the carrier gas, control the growth temperature to be 970 - 1050 °C, the growth time to be 100 - 200 s, the growth pressure to be 150 - 200 torr, and the V / III ratio to be 500 - 600;

[0030] S7, grow a quantum well layer on the surface of the high-temperature GaN decomposition layer, successively including:

[0031] In 0.2 Ga 0.8 N well layer: Use triethylgallium as the gallium source, trimethylindium as the indium source, NH 3 as the nitrogen source, N 2 as the carrier gas, control the growth temperature to be 765 °C, the growth time to be 100 - 200 s, the pressure to be 200 torr, and the V / III ratio to be 900 - 1100;

[0032] GaN barrier layer: Use trimethylgallium as the gallium source, NH 3 as the nitrogen source, N 2 as the carrier gas, control the growth temperature to be 765 °C, the growth time to be 200 - 300 s, the growth pressure to be 200 torr, and the V / III ratio to be 2000 - 2200;

[0033] In 0.3 Ga 0.7 N well layer: Use triethylgallium as the gallium source, trimethylindium as the indium source, NH 3 as the nitrogen source, N 2 as the carrier gas, control the growth temperature to be 720 °C, the growth time to be 100 - 200 s, the growth pressure to be 200 torr, and the V / III ratio to be 1000 - 1200;

[0034] Al 0.1 Ga 0.9 N barrier layer: Use trimethylgallium as the gallium source, trimethylaluminum as the aluminum source, NH3 Using trimethylgallium as the gallium source, trimethylindium as the indium source, NH 2 as the nitrogen source, and N

[0035] In 0.3 Ga 0.7 N well layer: Using trimethylgallium as the gallium source, trimethylindium as the indium source, NH 3 as the nitrogen source, and N 2 as the carrier gas, controlling the growth temperature at 720 °C, the growth time at 150 - 250 s, the growth pressure at 200 torr, and the V / III ratio at 2300 - 2500;

[0036] Al 0.1 Ga 0.9 N barrier layer: Using trimethylgallium as the gallium source, trimethylaluminum as the aluminum source, NH 3 as the nitrogen source, and N 2 as the carrier gas, controlling the growth temperature at 720 °C, the growth time at 150 - 250 s, the growth pressure at 200 torr, and the V / III ratio at 2300 - 2500;

[0037] S8, growing a p-GaN layer on the surface of the quantum well layer: Using trimethylgallium as the gallium source, bis(cyclopentadienyl)magnesium as the magnesium source, NH 3 as the nitrogen source, and N 2 as the carrier gas, controlling the growth temperature at 950 - 1000 °C, the growth time at 2000 - 3000 s, the growth pressure at 150 torr, and the V / III ratio at 1000 - 1200;

[0038] S9, growing a p + -GaN layer on the surface of the p-GaN layer: Using trimethylgallium as the gallium source, bis(cyclopentadienyl)magnesium as the magnesium source, NH 3 as the nitrogen source, and N 2 as the carrier gas, controlling the growth temperature at 860 - 885 °C, the growth time at 500 - 700 s, the growth pressure at 180 torr, and the V / III ratio at 600 - 800;

[0039] S10, annealing the structure obtained in step S9 in an N 2 atmosphere at 600 - 700 °C for 700 - 900 s, and then cooling to room temperature to obtain a GaN-based LED based on a high In-component thermally decomposed superlattice layer.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] 1. By introducing a high-In composition thermally decomposed superlattice layer, a medium-temperature GaN repair layer, and a high-temperature GaN decomposition layer, the InGaN in the high-In composition thermally decomposed superlattice layer is decomposed by the high-temperature GaN decomposition layer to generate voids, thereby releasing stress. At the same time, the medium-temperature GaN repair layer is used to restore the quality damage caused by the decomposition, so as to more fully release the stress, improve the piezoelectric polarization effect caused by lattice mismatch, weaken the quantum-confined Stark effect of the LED device, and improve the LED luminous efficiency.

[0042] 2. By effectively introducing a high-In composition thermally decomposed superlattice layer, a medium-temperature GaN repair layer, and a high-temperature GaN decomposition layer, the stress is effectively released, the content of In composition in the quantum well region can be increased, the emission of a longer peak wavelength is achieved, and a more efficient LED is obtained.

[0043] 3. The GaN cap layer in the high-In composition thermally decomposed superlattice layer of the present invention can prevent the premature decomposition of the InGaN decomposition layer when growing the high-temperature GaN decomposition layer. By simultaneously setting a medium-temperature GaN repair layer and a high-temperature GaN decomposition layer on the high-In composition thermally decomposed superlattice layer, the two GaN layers with different temperatures cooperate. On the one hand, it can repair the problems of poor crystal quality and surface morphology of the lower superlattice, and on the other hand, it can achieve strain relaxation, more fully release the stress, and realize a higher-performance LED.

[0044] 4. The wafer fabricated by the process of the present invention has good light emission uniformity and a low standard deviation of emission wavelength, which is beneficial to commercialization.

[0045] 5. Compared with the existing GaN-based LEDs based on superlattice layers, the device performance of the present invention is significantly improved, and the external quantum efficiency is maintained while the emission wavelength is increased.

[0046] 6. The preparation process of the GaN-based LED of the present invention based on the high-In composition thermally decomposed superlattice layer is simple, without complex processes such as electrochemical etching, and is easier to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a schematic diagram of each layer structure of the GaN-based LED of the present invention based on the high-In composition thermally decomposed superlattice;

[0048] Figure 2 It is a schematic diagram of the preparation process of the GaN-based LED of the present invention based on the high-In composition thermally decomposed superlattice;

[0049] Figure 3 It is a cross-sectional and top-view schematic diagram of the voids generated by the decomposition of the InGaN decomposition layer in Example 1;

[0050] Figure 4 It is an atomic force microscope (AFM) image of the high-temperature GaN decomposition layer in Example 1;

[0051] Figure 5 It is a scanning transmission electron microscope (STEM) image of the GaN-based LED in Example 1.

[0052] Figure 6 It is a Raman comparison image of the GaN layer under the quantum well in Example 1 and Comparative Example 1.

[0053] Figure 7 It is the electroluminescence spectrum of the GaN-based LED in Example 1 at different current densities of 1 - 10 A / cm 2 .

[0054] Figure 8 It is a comparison image of the peak wavelengths of the LEDs obtained in Example 1 and Comparative Example 1 at different current densities of 0 - 100 A / cm 2 .

[0055] Figure 9 It is a comparison image of the external quantum efficiencies of the LEDs obtained in Example 1 and Comparative Example 1 at different current densities of 0 - 100 A / cm 2 . Detailed implementation manners

[0056] The following combines the accompanying drawings and examples to further describe in detail the detailed implementation manners of the present invention

[0057] Example 1

[0058] As Figure 1 shown, the GaN-based LED provided in this example based on a high-In composition thermally decomposed superlattice layer is sequentially deposited from bottom to top on a sapphire substrate with: a u-GaN layer, an n-GaN layer, a high-In composition thermally decomposed superlattice layer, a medium-temperature GaN repair layer, a high-temperature GaN decomposition layer, a quantum well layer, a p-GaN layer, a p + -GaN layer; where: the high-In composition thermally decomposed superlattice layer includes 3 groups of InGaN decomposition layers and GaN cap layers (one InGaN decomposition layer and one GaN cap layer form a group) stacked in sequence and cyclically. From bottom to top on the quantum well layer, there are sequentially included In 0.2 Ga 0.8 N well layer, GaN barrier layer, In 0.3 Ga 0.7 N well layer, Al 0.1 Ga 0.9 N barrier layer, In 0.3 Ga 0.7 N well layer, Al 0.1 Ga 0.9 N barrier layer.

[0059] As Figure 2As shown in the figure, the preparation method of the GaN-based LED based on the high In-component thermal decomposition superlattice layer in this embodiment includes the following steps:

[0060] S1. At a temperature of 1000 °C, the patterned sapphire substrate is reduced in an H 2 atmosphere for 300 s to remove surface impurities and oxides.

[0061] S2. Grow a u-GaN layer on the surface of the sapphire substrate: Using trimethylgallium as the gallium source, NH 3 as the nitrogen source, and H 2 as the carrier gas, controlling the growth temperature at 1100 °C, the growth time at 3200 s, the growth pressure at 400 torr, and the V / III ratio at 1100. The thickness of the obtained u-GaN layer is 3 μm.

[0062] S3. Grow an n-GaN layer on the surface of the u-GaN layer: Using trimethylgallium as the gallium source, NH 3 as the nitrogen source, SiH 4 as the silicon source, and H 2 as the carrier gas, controlling the growth temperature at 1080 °C, the growth time at 1600 s, the growth pressure at 400 torr, and the V / III ratio at 752. The thickness of the obtained n-GaN layer is 2 μm.

[0063] S4. Sequentially and cyclically grow an InGaN decomposition layer and a GaN cap layer on the surface of the n-GaN layer:

[0064] InGaN decomposition layer: Using triethylgallium as the gallium source, trimethylindium as the indium source, NH 3 as the nitrogen source, and N 2 as the carrier gas, controlling the reaction temperature at 720 °C, the growth time at 150 s, the growth pressure at 200 torr, and the V / III ratio at 1056. The thickness of the obtained InGaN decomposition layer is 2.2 nm.

[0065] GaN cap layer: Using trimethylgallium as the gallium source, NH 3 as the nitrogen source, and N 2 as the carrier gas, controlling the reaction temperature at 720 °C, the growth time at 220 s, the growth pressure at 200 torr, and the V / III ratio at 2650. The thickness of the obtained GaN cap layer is 3 nm.

[0066] S5. Grow a medium-temperature GaN repair layer on the surface of the high In-component thermal decomposition superlattice layer: Using trimethylgallium as the gallium source, NH 3 as the nitrogen source, and N 2 as the carrier gas, controlling the growth temperature at 865 °C, the growth time at 320 s, the growth pressure at 200 torr, and the V / III ratio at 1141. The thickness of the obtained medium-temperature GaN repair layer is 125 nm.

[0067] S6, grow a high-temperature GaN decomposition layer on the surface of the intermediate-temperature GaN repair layer: Use trimethylgallium as the gallium source, NH 3 as the nitrogen source, and N 2 as the carrier gas. Control the growth temperature at 1000 °C, the growth time at 130 s, the pressure at 200 torr, and the V / III ratio at 506. The thickness of the obtained high-temperature GaN decomposition layer is 25 nm.

[0068] S7, grow a quantum well layer on the surface of the high-temperature GaN decomposition layer, which successively includes:

[0069] In 0.2 Ga 0.8 N well layer: Use triethylgallium as the gallium source, trimethylindium as the indium source, NH 3 as the nitrogen source, and N 2 as the carrier gas. Control the growth temperature at 765 °C, the growth time at 140 s, the pressure at 200 torr, and the V / III ratio at 1000. The thickness of the obtained In 0.2 Ga 0.8 N well layer is 3 nm.

[0070] GaN barrier layer: Use trimethylgallium as the gallium source, NH 3 as the nitrogen source, and N 2 as the carrier gas. Control the growth temperature at 765 °C, the growth time at 270 s, the pressure at 200 torr, and the V / III ratio at 2100. The thickness of the obtained GaN barrier layer is 9 nm.

[0071] In 0.3 Ga 0.7 N well layer: Use triethylgallium as the gallium source, trimethylindium as the indium source, NH 3 as the nitrogen source, and N 2 as the carrier gas. Control the growth temperature at 720 °C, the growth time at 150 s, the growth pressure at 200 torr, and the V / III ratio at 1155. The thickness of the obtained In 0.3 Ga 0.7 N well layer is 3 nm.

[0072] Al 0.1 Ga 0.9 N barrier layer: Use trimethylgallium as the gallium source, trimethylaluminum as the aluminum source, NH 3 as the nitrogen source, and N 2 as the carrier gas. Control the growth temperature at 720 °C, the growth time at 200 s, the growth pressure at 200 torr, and the V / III ratio at 2320. The thickness of the obtained Al 0.1 Ga 0.9 N barrier layer is 6 nm.

[0073] In 0.3Ga 0.7 N-well layer: Triethylgallium is used as the gallium source, trimethylindium is used as the indium source, NH 3 is used as the nitrogen source, N 2 is used as the carrier gas. The growth temperature is controlled at 720 °C, the growth time is 150 s, the growth pressure is 200 torr, and the V / III ratio is 1155. The obtained In 0.3 Ga 0.7 N-well layer has a thickness of 3 nm.

[0074] Al 0.1 Ga 0.9 N-barrier layer: Trimethylgallium is used as the gallium source, trimethylaluminum is used as the aluminum source, NH 3 is used as the nitrogen source, N 2 is used as the carrier gas. The growth temperature is controlled at 720 °C, the growth time is 200 s, the growth pressure is 200 torr, and the V / III ratio is 2320. The obtained Al 0.1 Ga 0.9 N-barrier layer has a thickness of 6 nm.

[0075] S8. For growing the p-GaN layer on the surface of the quantum well layer: Trimethylgallium is used as the gallium source, bis(cyclopentadienyl)magnesium is used as the magnesium source, NH 3 is used as the nitrogen source, N 2 is used as the carrier gas. The growth temperature is controlled at 960 °C, the growth time is 2300 s, the growth pressure is 150 torr, and the V / III ratio is 1072. The obtained p-GaN layer has a thickness of 80 nm.

[0076] S9. For growing the p + -GaN layer on the surface of the p-GaN layer: Trimethylgallium is used as the gallium source, bis(cyclopentadienyl)magnesium is used as the magnesium source, NH 3 is used as the nitrogen source, N 2 is used as the carrier gas. The growth temperature is controlled at 885 °C, the growth time is 510 s, the growth pressure is 180 torr, and the V / III ratio is 615. The obtained p + -GaN layer has a thickness of 3 nm.

[0077] S10. Anneal the structure obtained in step S9 in an N 2 atmosphere at 650 °C for 750 s, and then cool it down to room temperature to obtain a GaN-based LED based on a high-In-component thermally decomposed superlattice layer.

[0078] Figure 3 It is the cross-sectional view and top view of the voids generated by the decomposition of the InGaN decomposition layer. In the process of S6, the high-temperature grown GaN decomposition layer causes the high-In-content InGaN layer grown in S4 to decompose and generate voids, thereby relaxing the strain of the GaN layer above the superlattice layer.

[0079] Figure 4It is an atomic force microscope (AFM) image of the high-temperature GaN decomposition layer, and the root mean square (RMS) of the surface roughness of the sample is less than 0.5 nm. The medium-temperature GaN repair layer introduced in the S5 process avoids surface deterioration caused by the decomposition of the superlattice layer, making the surface roughness of the upper-layer GaN at a relatively low level.

[0080] Figure 5 It is a scanning transmission electron microscope (STEM) image of the GaN-based LED prepared in this embodiment. It can be observed that voids are generated due to the decomposition of the InGaN decomposition layer in the thermally decomposed superlattice layer.

[0081] Comparative Example 1

[0082] To verify the influence of the high-In composition thermally decomposed superlattice layer on the LED performance, a GaN-based LED without the high-In composition thermally decomposed superlattice layer was prepared in this comparative example. Compared with the device structure in Example 1, the difference is only that there is no high-In composition thermally decomposed superlattice layer, medium-temperature GaN repair layer, and high-temperature GaN decomposition layer. Compared with the preparation method in Example 1, the difference is only that steps S4, S5, and S6 were not carried out.

[0083] Figure 6 It is a Raman comparison diagram of the GaN layer below the quantum well with and without the high-In composition thermally decomposed superlattice layer in Example 1 and Comparative Example 1. The E 2 (high) peak of non-stressed gallium nitride is located at 566.2 cm -1 , the redshift of the n-GaN layer below the quantum well in Comparative Example 1 is 6.6 cm -1 , while the redshift of the high-temperature GaN decomposition layer below the quantum well in Example 1 is 4.9 cm -1 . The calculated stress of the n-GaN layer below the quantum well in Comparative Example 1 is 2.58 GPa, and the calculated stress of the high-temperature GaN decomposition layer below the quantum well in Example 1 is 1.91 GPa. It can be seen that the compressive stress on the GaN layer below the quantum well in Example 1 is smaller.

[0084] Figure 7 It is an electroluminescence spectrum diagram of the GaN-based LED prepared in Example 1 at different current densities from 1 - 10 A / cm 2 . It can be seen from the figure that the LED has no parasitic blue emission.

[0085] Figure 8 and Figure 9 are respectively the peak wavelength comparison diagram and external quantum efficiency comparison diagram of the LEDs obtained in Example 1 and Comparative Example 1 at different current densities from 0 - 100 A / cm 2 . It can be seen from the figure that at a current density of 1 A / cm 2When there is a high-In composition thermally decomposed superlattice layer, the peak wavelength of the LED is 18 nm higher than that of the LED without the high-In composition thermally decomposed superlattice layer, while the external quantum efficiency only decreases by 1.4%. Due to the insertion of the high-In composition thermally decomposed superlattice layer, the crystal quality decreases slightly, but the external quantum efficiency only decreases slightly when the wavelength is increased.

[0086] The above are only exemplary embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. GaN-based LED based on high In content thermal decomposition superlattice layer, characterized in that: The following are deposited on the sapphire substrate from bottom to top: u-GaN layer, n-GaN layer, high In component thermal decomposition superlattice layer, medium temperature GaN repair layer, high temperature GaN decomposition layer, quantum well layer, p-GaN layer, p + -GaN layer; the high In component thermal decomposition superlattice layer comprises 2 to 5 groups of InGaN decomposition layers and GaN cap layers which are cyclically stacked in sequence.

2. The GaN-based LED based on a high In content thermal decomposition superlattice layer according to claim 1, characterized in that: The growth temperature of the u-GaN layer is 1050-1150° C., and the growth thickness is 2-4 μm.

3. The GaN-based LED based on a high In content thermal decomposition superlattice layer according to claim 1, characterized in that: The growth temperature of the n-GaN layer is 1000-1200°C, the growth thickness is 2-5 μm, and Si doping is used with a doping concentration of 1×10 19 ~1.5×10 19 cm -3 .

4. The GaN-based LED based on a high In content thermal decomposition superlattice layer according to claim 1, characterized in that: In the high In component thermal decomposition superlattice layer: the In molar percentage of the InGaN decomposition layer is 25-30%; the growth temperature of the InGaN decomposition layer and the GaN cap layer is 700-750°C, and the growth pressure is 180-250 torr; the thickness of the InGaN decomposition layer is 2-2.5nm, and the thickness of the GaN cap layer is 3-4nm.

5. The GaN-based LED based on a high In content thermal decomposition superlattice layer according to claim 1 or 4, characterized in that: In the high In component thermal decomposition superlattice layer: the V / III ratio of the InGaN decomposition layer growth is 1000-1200, and the V / III ratio of the GaN cap layer growth is 2600-2800.

6. The GaN-based LED based on a high In content thermal decomposition superlattice layer according to claim 1, characterized in that: The growth temperature of the medium-temperature GaN repair layer is 850-870° C., the growth pressure is 150-200 torr, the grown V / III ratio is 1100-1250, and the thickness is 110-130 nm.

7. The GaN-based LED based on a high In content thermal decomposition superlattice layer according to claim 1, characterized in that: The growth temperature of the high-temperature GaN decomposition layer is 970-1050° C., the growth pressure is 150-200 torr, the growth V / III ratio is 500-600, and the thickness is 20-30 nm.

8. The GaN-based LED based on a high In content thermal decomposition superlattice layer according to claim 1, characterized in that: The quantum well layer includes In with a thickness of 3 nm from bottom to top. 0.2 Ga 0.8 N well layer, GaN barrier layer with a thickness of 9nm, In 0.3 Ga 0.7 N well layer, Al with a thickness of 6nm 0.1 Ga 0.9 N barrier layer, In with a thickness of 3nm 0.3 Ga 0.7 N well layer, Al with a thickness of 6nm 0.1 Ga 0.9 N barrier layers, where In 0.2 Ga 0.8 The growth temperature of the N well layer and GaN barrier layer is 765℃, In 0.3 Ga 0.7 N well layer and Al 0.1 Ga 0.9 The growth temperature of the N barrier layer is 720°C.

9. The GaN-based LED based on a high In content thermal decomposition superlattice layer according to claim 1, characterized in that: The p-GaN layer has a thickness of 70-90 nm, a growth temperature of 950-1000° C., and is doped with Mg at a doping concentration of 2×10 20 ~2.5×10 20 cm -3 ; said p + -GaN layer thickness is 2-5nm, growth temperature is 860-885℃, Mg doping is used, and doping concentration is 4×10 21 ~5×10 21 cm -3 .

10. A method for preparing a GaN-based LED based on a high In content thermal decomposition superlattice layer as claimed in any one of claims 1 to 9, characterized in that: The steps include: S1, performing a reduction treatment on the patterned sapphire substrate in a H2 atmosphere at a temperature of 950-1100°C for 200-400s to remove surface impurities and oxides; S2, growing a u-GaN layer on the surface of a sapphire substrate: using trimethylgallium as a gallium source, NH3 as a nitrogen source, and H2 as a carrier gas, controlling the growth temperature to be 1050-1150°C, the growth time to be 3000-3500s, the growth pressure to be 400torr, and the V / III ratio to be 1000-1200; S3, growing an n-GaN layer on the surface of the u-GaN layer: using trimethylgallium as a gallium source, NH3 as a nitrogen source, SiH4 as a silicon source, and H2 as a carrier gas, controlling the growth temperature to be 1000-1200°C, the growth time to be 1500-1800s, the growth pressure to be 400torr, and the V / III ratio to be 600-800; S4, cyclically growing an InGaN decomposition layer and a GaN cap layer on the surface of the n-GaN layer: InGaN decomposition layer: triethylgallium is used as gallium source, trimethylindium is used as indium source, NH3 is used as nitrogen source, and N2 is used as carrier gas. The growth temperature is controlled at 700-750°C, the growth time is 100-200s, the growth pressure is 180-250torr, and the V / III ratio is 1000-1200. GaN cap layer: trimethylgallium is used as gallium source, NH3 is used as nitrogen source, and N2 is used as carrier gas. The growth temperature is controlled at 700-750°C, the growth time is 200-300s, the growth pressure is 180-250torr, and the V / III ratio is 2600-2800. S5, growing a medium-temperature GaN repair layer on the surface of the high In component thermal decomposition superlattice layer: using trimethylgallium as a gallium source, NH3 as a nitrogen source, and N2 as a carrier gas, controlling the growth temperature to be 850-870°C, the growth time to be 300-400s, the growth pressure to be 150-200torr, and the V / III ratio to be 1100-1250; S6, growing a high-temperature GaN decomposition layer on the surface of the medium-temperature GaN repair layer: using trimethylgallium as a gallium source, NH3 as a nitrogen source, N2 as a carrier gas, controlling the growth temperature to be 970-1050°C, the growth time to be 100-200s, the growth pressure to be 150-200torr, and the V / III ratio to be 500-600; S7, growing a quantum well layer on the surface of the high-temperature GaN decomposition layer, sequentially comprising: In 0.2 Ga 0.8 N well layer: triethylgallium as gallium source, trimethylindium as indium source, NH3 as nitrogen source, N2 as carrier gas, control growth temperature to 765°C, growth time to 100-200s, pressure to 200torr, V / III ratio to 900-1100; GaN barrier layer: trimethylgallium is used as gallium source, NH3 is used as nitrogen source, and N2 is used as carrier gas. The growth temperature is controlled to be 765°C, the growth time is 200-300s, the growth pressure is 200torr, and the V / III ratio is 2000-2200. In 0.3 Ga 0.7 N well layer: triethylgallium as gallium source, trimethylindium as indium source, NH3 as nitrogen source, N2 as carrier gas, control growth temperature to 720°C, growth time to 100-200s, growth pressure to 200torr, V / III ratio to 1000-1200; Al 0.1 Ga 0.9 N barrier layer: trimethylgallium is used as gallium source, trimethylaluminum is used as aluminum source, NH3 is used as nitrogen source, and N2 is used as carrier gas. The growth temperature is controlled to be 720°C, the growth time is 150-250s, the growth pressure is 200torr, and the V / III ratio is 2300-2500. In 0.3 Ga 0.7 N well layer: triethylgallium as gallium source, trimethylindium as indium source, NH3 as nitrogen source, N2 as carrier gas, control growth temperature to 720°C, growth time to 100-200s, growth pressure to 200torr, V / III ratio to 1000-1200; Al 0.1 Ga 0.9 N barrier layer: trimethylgallium is used as gallium source, trimethylaluminum is used as aluminum source, NH3 is used as nitrogen source, and N2 is used as carrier gas. The growth temperature is controlled to be 720°C, the growth time is 150-250s, the growth pressure is 200torr, and the V / III ratio is 2300-2500. S8, growing a p-GaN layer on the surface of the quantum well layer: using trimethylgallium as a gallium source, bismuth magnesium as a magnesium source, NH3 as a nitrogen source, and N2 as a carrier gas, controlling the growth temperature to be 950-1000°C, the growth time to be 2000-3000s, the growth pressure to be 150torr, and the V / III ratio to be 1000-1200; S9, growing p on the surface of the p-GaN layer + -GaN layer: trimethylgallium as gallium source, bismuth magnesium as magnesium source, NH3 as nitrogen source, N2 as carrier gas, control the growth temperature to 860-885°C, growth time to 500-700s, growth pressure to 180torr, V / III ratio to 600-800; S10, annealing the structure obtained in step S9 at 600-700°C for 700-900s in a N2 atmosphere, and then cooling to room temperature to obtain a GaN-based LED based on a high In component thermal decomposition superlattice layer.

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