GaN-based white light epitaxial structure and growth method thereof

Abstract

The application relates to the technical field of semiconductors, in particular to a GaN-based white light epitaxial structure and a growth method thereof. The GaN-based white light epitaxial structure comprises, from top to bottom, a P-GaN layer, a multi-quantum layer, an N-GaN layer, an AlN-layer, an AlN+ layer and a sapphire substrate. The GaN-based white light epitaxial structure uses the AlN+ layer and the AlN-layer to replace a traditional buffer layer, a U-GaN layer and an N-type AlGaN layer, so as to reduce dislocations and improve the crystal quality.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor, in particular to a GaN-based white light epitaxial structure and a growth method thereof. BACKGROUND

[0002] Gallium nitride (GaN) has become a representative of the third generation of semiconductor materials due to its stable chemical properties, thermal stability, high temperature resistance and other advantages. At present, GaN-based LED is attracting more and more attention and research, and its epitaxial structure mainly includes substrate, buffer layer, U-GaN layer, nAl, nGaN layer, multi-quantum step active region, and P-type layer. When current passes through, the electrons in the N-type region and the holes in the P-type region enter the multi-quantum step active region and recombine to emit visible light of the required wavelength. Sapphire substrate (PSS) is the earliest and most widely used substrate in the preparation of light-emitting diodes. However, there is a large lattice mismatch and thermal mismatch between sapphire and GaN. The large lattice mismatch and thermal mismatch will result in a high dislocation in the GaN thin film material grown on the sapphire substrate, and will also make the epitaxial layer more prone to warping and cracking, making the subsequent processing process difficult.

[0003] In the epitaxial preparation of GaN-based LED, the large lattice mismatch and thermal mismatch have always been an important factor affecting the electrical properties of LED. The main way to handle dislocations in China is to grow a buffer layer and a GaN intrinsic layer between the substrate and GaN to reduce the large lattice mismatch and thermal mismatch between the epitaxial layer and the hetero-substrate. For example, the Chinese utility model patent with publication number CN209561451U discloses a GaN-based light-emitting diode epitaxial wafer, which includes a sapphire substrate layer, a buffer layer, a U-GaN layer, an nGaN, an MQW light-emitting layer, an LT-pGaN layer, and an HT-pGaN layer. However, this structure has limited effect on dislocations, and the growth cost is high. SUMMARY

[0004] In order to overcome the defects of the prior art, the technical problem to be solved by the present application is to provide a GaN-based white light epitaxial structure and a growth method thereof which can reduce dislocations.

[0005] In order to solve the above technical problems, the technical scheme adopted by the present application is as follows: a GaN-based white light epitaxial structure, which comprises, from top to bottom, a P-GaN layer, a multi-quantum layer, an N-GaN layer, an AlN-layer, an AlN+ layer, and a sapphire substrate.

[0006] Another technical scheme of the present application is a growth method of a GaN-based white light epitaxial structure, which comprises growing an AlN+ layer, an AlN-layer, an N-GaN layer, a multi-quantum layer, and a P-GaN layer on a sapphire substrate in sequence.

[0007] The GaN-based white light epitaxial structure of the present application has the beneficial effect that the AlN+ layer and the AlN- layer are arranged between the N-GaN layer and the sapphire substrate to replace the traditional buffer layer, the U-GaN layer and the N-type AlGaN layer, which can more efficiently reduce the lattice mismatch and thermal mismatch between the epitaxial layer and the hetero-substrate, reduce dislocations, improve the crystal quality and further promote the production capacity. BRIEF DESCRIPTION OF DRAWINGS

[0008] Figure 1 Fig. 1 shows a structure schematic diagram of the epitaxial structure of the embodiment one of the present application;

[0009] Figure 2 Fig. 2 shows a structure schematic diagram of the epitaxial structure of the comparative example one of the present application;

[0010] Figure 3 Fig. 3 shows a dislocation comparison diagram of the epitaxial structure of the embodiment one of the present application. DETAILED DESCRIPTION

[0011] To make the technical content, the achieved purposes and effects of the present application clear, the following will be described in combination with the embodiments and the accompanying drawings.

[0012] The most key idea of the present application is to use the AlN+ layer and the AlN- layer to replace the traditional buffer layer, the U-GaN layer and the N-type AlGaN layer, which can reduce dislocations and improve the crystal quality.

[0013] Please refer to Figure 1 Fig. 1 shows the GaN-based white light epitaxial structure of the present application, which comprises a P-GaN layer, a multi-quantum layer, an N-GaN layer, an AlN- layer, an AlN+ layer and a sapphire substrate arranged in sequence from top to bottom.

[0014] From the above description, it can be known that the present application has the beneficial effect that the AlN+ layer and the AlN- layer are arranged between the N-GaN layer and the sapphire substrate to replace the traditional buffer layer, the U-GaN layer and the N-type AlGaN layer, which can more efficiently reduce the lattice mismatch and thermal mismatch between the epitaxial layer and the hetero-substrate, reduce dislocations, improve the crystal quality and further promote the production capacity.

[0015] Further, a stress release layer is arranged between the N-GaN layer and the light-emitting layer.

[0016] From the above description, it can be known that the stress release layer K can eliminate the stress caused by the lattice mismatch in the LED.

[0017] Further, an electron blocking layer is arranged between the multi-quantum layer and the P-GaN layer.

[0018] From the above description, the introduction of the electron blocking layer improves the restriction ability to electrons and improves the injection rate of holes, thereby improving the internal quantum efficiency and the luminous efficiency.

[0019] Further, the P-GaN layer is provided with a P-type contact layer away from the side of the multi-quantum layer.

[0020] Another technical solution of the present application is a growth method of a GaN-based white light epitaxial structure, which sequentially grows an AlN+ layer, an AlN- layer, an N-GaN layer, a multi-quantum layer and a P-GaN layer on a sapphire substrate.

[0021] From the above description, the present application proposes a GaN-based epitaxial structure growth method which better reduces dislocations, uses a bottom layer formed by sequentially stacking an AlN+ layer and an AlN- layer grown in a PVD (physical vapor deposition) reaction chamber, and replaces the traditional bottom layer of a buffer layer, a U-GaN layer and an N-type AlGaN layer produced in a MOCVD (metal organic chemical vapor deposition) reaction chamber. The bottom layer formed by the AlN+ layer and the AlN- layer has a low dislocation density. The AlN+ layer forms a three-dimensional "island" surface during growth, and the AlN- layer grows in a two-dimensional layer form. The growth of a two-dimensional layer structure on a three-dimensional "island" surface can reduce the dislocations of the epitaxial structure, reduce stress, and replace the original buffer layer and U-GaN layer. It also improves the crystal quality and greatly reduces the production cost.

[0022] The PVD growth bottom layer has advantages over the MOCVD growth bottom layer, can reduce dislocations, improve crystal quality, and reduce costs.

[0023] Further, the AlN+ layer is grown in a reaction chamber, the temperature of the reaction chamber is 550-750℃, 20-40sccm argon, 150-240sccm nitrogen and 1-2sccm oxygen are introduced into the reaction chamber, and the duration is 5-10min. Preferably, the temperature of the reaction chamber is 600-700℃.

[0024] From the above description, the temperature during the growth of the AlN+ layer is 550-750℃, which can increase the energy during the AlN film formation on the substrate, promote crystallization, and realize preferential growth of a specific crystal orientation. The Al content of the AlN+ layer is lower than that of the Al- layer.

[0025] Further, the thickness of the AlN+ layer is 250-320nm. Preferably, the thickness of the AlN+ layer is 280-300nm.

[0026] Further, the AlN- layer is grown in a reaction chamber with a temperature of 600-700 °C, and 30-70 seem of argon, 150-240 seem of nitrogen and 1.5-2.5 seem of oxygen are introduced into the reaction chamber for 3-6 min.

[0027] Further, the AlN- layer has a thickness of 140-220 nm. Preferably, the AlN- layer has a thickness of 170-200 nm.

[0028] From the above description, it can be seen that the thickness of the AlN+ layer and the AlN- layer affects the crystalline quality of the n-type GaN grown on the AlN layer.

[0029] Further, after the AlN- layer is grown, the temperature is cooled for 4-6 min.

[0030] Further, the stress release layer comprises a stack structure of 5-8 groups of N-AlGaN layers and GaN layers.

[0031] Further, the N-AlGaN layer is doped with Si, and the N-AlGaN layer is grown in a reaction chamber with a temperature of 900-1200 °C and a pressure of 100 Torr-300 Torr, and the GaN layer is grown in a reaction chamber with a temperature of 900-1200 °C and a pressure of 100 Torr-300 Torr.

[0032] Further, the multi-quantum well layer comprises a stack structure of 14-16 groups of In x Ga 1-x N(0 < x < 1) layers and GaN layers, the In x Ga 1-x N(0 < x < 1) layer has a thickness of 3-5 nm, and the GaN layer has a thickness of 9-15 nm.

[0033] Further, the total thickness of the multi-quantum well layer is ≤300 nm, and the thickness of the stack structure is ≤20.

[0034] Further, the In x Ga 1-x N(0 < x < 1) layer is grown in a reaction chamber with a temperature of 800 °C and a pressure of 100-300 Torr.

[0035] Further, the electron blocking layer is a P-type Al y Ga 1-y N(0.1 < y < 0.5) electron blocking layer with a thickness of 40-90 nm, and the electron blocking layer is grown in a reaction chamber with a temperature of 850-1080 °C and a pressure of 200-500 Torr.

[0036] Further, the P-type contact layer is grown in the reaction chamber at a temperature of 850-1080℃ and a pressure of 100-300Torr.

[0037] Further, after the P-type contact layer is grown, the temperature of the reaction chamber is set to 650-850℃ for 5-15min.

[0038] From the above description, it is known that this step is annealing, which has an activation effect and can also slow down the cooling curve, thereby protecting the machine.

[0039] Further, the AlN+ layer, the AlN- layer, the N-GaN layer, the stress release layer, the multi-quantum layer, the electron blocking layer, the P-GaN layer and the P-type contact layer are sequentially grown on the sapphire substrate.

[0040] Please refer to Figure 1 The embodiment one of the present application is a growth method of a GaN-based white light epitaxial structure, comprising the following steps:

[0041] S1: The sapphire substrate is placed in a PVD reaction chamber, the temperature of the PVD reaction chamber is set to 550-750℃, 30sccm argon, 200sccm nitrogen and 1.5sccm oxygen are introduced into the PVD reaction chamber for 7min, and an AlN+ layer with a thickness of 280nm is formed;

[0042] S2: The temperature of the PVD reaction chamber is set to 650℃, 50sccm argon, 200sccm nitrogen and 2sccm oxygen are introduced into the PVD reaction chamber for 4min, and an AlN- layer with a thickness of 170nm is formed;

[0043] S3: After 5min of cooling, the substrate is moved from the PVD reaction chamber to a MOCVD reaction chamber;

[0044] S4: The temperature of the MOVCD reaction chamber is set to 1050℃ and the pressure is set to 200Torr, and a 2.5um N-GaN layer doped with Si is grown, wherein the doping concentration of Si is 5*10 18 atom / cm 3 ;

[0045] S5: A 20nm N-AlGaN layer doped with Si and a 10nm GaN layer are sequentially grown;

[0046] When the N-AlGaN layer doped with Si is grown, the temperature of the MOVCD reaction chamber is set to 1000℃ and the pressure is set to 200Torr, wherein the doping concentration of Si is 5*10 18 atom / cm 3 ;

[0047] When growing the GaN layer, the temperature of the MOVCD reaction cavity is set to 1000 degrees, and the pressure is 200 Torr;

[0048] S6: The S5 is repeated for 9 times to form a stress release layer;

[0049] S7: 4nm In x Ga 1-x N (0 < x < 1) layer and 12nm GaN layer are sequentially grown;

[0050] When growing the In x Ga 1-x N (0 < x < 1) layer, the temperature of the MOVCD reaction cavity is set to 800 degrees, and the pressure is 200 Torr;

[0051] When growing the GaN layer, the temperature of the MOVCD reaction cavity is set to 900 degrees, and the pressure is 200 Torr;

[0052] S8: The S7 is repeated for 15 times to form a multi-quantum well layer;

[0053] S9: The temperature of the MOVCD reaction cavity is set to 950 degrees, and the pressure is 400 Torr, and a 70nm P-type Al y Ga 1-y N (0.1 < y < 0.5) electron blocking layer is grown;

[0054] S10: The temperature of the MOVCD reaction cavity is set to 890 degrees, and the pressure is 200 Torr, and a 450nm P-type GaN layer is grown;

[0055] S11: The temperature of the MOVCD reaction cavity is set to 900 degrees, and the pressure is 200 Torr, and a 150nm P-type contact layer is grown;

[0056] S12: The temperature of the MOVCD reaction cavity is set to 750 degrees, and the duration is 10 minutes, and the preparation of the LED epitaxial structure is completed.

[0057] Embodiment two of the present application is a growth method of a GaN-based white light epitaxial structure, comprising the following steps:

[0058] S1: A sapphire substrate is placed in a PVD reaction cavity, the temperature of the PVD reaction cavity is set to 550-750 degrees, 20sccm argon, 150sccm nitrogen and 1sccm oxygen are introduced into the PVD reaction cavity, and the duration is 5 minutes, so as to form a 250nm AlN+ layer;

[0059] S2: Set the temperature of the PVD reaction chamber to 600°C, introduce 30 seem argon, 150 seem nitrogen and 1.5 seem oxygen into the PVD reaction chamber for 3 min, and form a 140 nm AlN layer;

[0060] S3: After 5 min of cooling, move the substrate from the PVD reaction chamber to the MOCVD reaction chamber;

[0061] S4: Set the temperature of the MOVCD reaction chamber to 1050°C and the pressure to 200 Torr, and grow a 2.5 um Si-doped N-GaN layer, wherein the Si doping concentration is 5*10 18 atom / cm 3 ;

[0062] S5: Grow a 20 nm Si-doped N-AlGaN layer and a 10 nm GaN layer in sequence;

[0063] When growing the Si-doped N-AlGaN layer, set the temperature of the MOVCD reaction chamber to 900°C and the pressure to 100 Torr, wherein the Si doping concentration is 5*10 18 atom / cm 3 ;

[0064] When growing the GaN layer, set the temperature of the MOVCD reaction chamber to 900°C and the pressure to 100 Torr;

[0065] S6: Repeat S5 for 8 times to form a stress release layer;

[0066] S7: Grow a 3 nm In x Ga 1-x N(0 < x < 1) layer and a 9 nm GaN layer in sequence;

[0067] When growing the In x Ga 1-x N(0 < x < 1) layer, set the temperature of the MOVCD reaction chamber to 800°C and the pressure to 100 Torr;

[0068] When growing the GaN layer, set the temperature of the MOVCD reaction chamber to 900°C and the pressure to 200 Torr;

[0069] S8: Repeat S7 for 14 times to form a multi-quantum well layer;

[0070] S9: Set the temperature of the MOVCD reaction chamber to 850-1080°C and the pressure to 200 Torr, and grow a 40 nm P-type Al y Ga 1-y N(0.1 < y < 0.5) electron blocking layer;

[0071] S10: set the temperature of the MOVCD reaction cavity to 890 DEG C, the pressure to 200 Torr, and grow a 450-nm P-type GaN layer;

[0072] S11: set the temperature of the MOVCD reaction cavity to 850 DEG C, the pressure to 100 Torr, and grow a 150-nm P-type contact layer;

[0073] S12: set the temperature of the MOVCD reaction cavity to 650 DEG C, and keep for 5-15 min, to complete the preparation of the LED epitaxial structure.

[0074] Embodiment three of the application is a growth method of a GaN-based white light epitaxial structure, comprising the following steps:

[0075] S1: place a sapphire substrate in a PVD reaction cavity, set the temperature of the PVD reaction cavity to 550-750 DEG C, introduce 40 sccm argon, 240 sccm nitrogen and 2 sccm oxygen into the PVD reaction cavity, and keep for 10 min, to form a 320-nm AlN+ layer;

[0076] S2: set the temperature of the PVD reaction cavity to 700 DEG C, introduce 70 sccm argon, 240 sccm nitrogen and 2.5 sccm oxygen into the PVD reaction cavity, and keep for 6 min, to form a 220-nm AlN- layer;

[0077] S3: cool for 5 min, and then move the substrate from the PVD reaction cavity to a MOCVD reaction cavity;

[0078] S4: set the temperature of the MOVCD reaction cavity to 1050 DEG C, the pressure to 200 Torr, and grow a 2.5-um Si-doped N-GaN layer, wherein the Si doping concentration is 5*10 18 atom / cm 3 ;

[0079] S5: sequentially grow a 20-nm Si-doped N-AlGaN layer and a 10-nm GaN layer;

[0080] When growing the Si-doped N-AlGaN layer, set the temperature of the MOVCD reaction cavity to 1200 DEG C, the pressure to 300 Torr, and the Si doping concentration to 5*10 18 atom / cm 3 ;

[0081] When growing the GaN layer, set the temperature of the MOVCD reaction cavity to 1200 DEG C, the pressure to 300 Torr;

[0082] S6: repeat S5 for 10 times, to form a stress release layer;

[0083] S7: Grow an In x Ga 1-x N (0 < x < 1) layer and a 15-nm GaN layer in sequence;

[0084] When growing the In x Ga 1-x N (0 < x < 1) layer, set the temperature of the MOVCD reaction chamber to 800 °C and the pressure to 300 Torr;

[0085] When growing the GaN layer, set the temperature of the MOVCD reaction chamber to 900 °C and the pressure to 200 Torr;

[0086] S8: Repeat S7 for 16 cycles to form a multi-quantum well layer;

[0087] S9: Set the temperature of the MOVCD reaction chamber to 1080 °C and the pressure to 500 Torr, and grow a 90-nm P-type Al y Ga 1-y N (0.1 < y < 0.5) electron blocking layer;

[0088] S10: Set the temperature of the MOVCD reaction chamber to 890 °C and the pressure to 200 Torr, and grow a 450-nm P-type GaN layer;

[0089] S11: Set the temperature of the MOVCD reaction chamber to 1080 °C and the pressure to 300 Torr, and grow a 150-nm P-type contact layer;

[0090] S12: Set the temperature of the MOVCD reaction chamber to 850 °C for 5 - 15 min to complete the preparation of the LED epitaxial structure.

[0091] Please refer to Figure 2 As shown, Comparative Example 1 of the present invention is: the growth method of a conventional GaN-based white light epitaxial structure.

[0092] The difference from Example 1 is that the following steps are used to replace S1 - S3 in Example 1.

[0093] Step 1: Place the sapphire substrate into the MOCVD reaction chamber, anneal the substrate in a hydrogen atmosphere for 8 min; set the temperature of the MOCVD reaction chamber to 1500 °C and nitridize the substrate;

[0094] Step 2: Set the temperature of the MOCVD reaction chamber to 800 °C and the pressure to 200 Torr, and grow a 30-nm buffer layer;

[0095] Step 3: Set the temperature of the MOCVD reaction chamber to 1100 °C and the pressure to 200 Torr for 6 min;

[0096] Step 4: set the temperature of the MOCVD reaction cavity to 1100℃, the pressure to 200 Torr, and grow a 3um U-GaN layer;

[0097] Step 5: set the temperature of the MOCVD reaction cavity to 900℃, the pressure to 300 Torr, and grow an 80nm N-type AlGaN layer.

[0098] The epitaxial structure of Example 1 and Comparative Example 1 is detected, the 102 plane half-width of Example 1 is 223.2 arcsec, the 002 plane half-width is 165.2 arcsec (see Figure 3 ), and the surface roughness is 0.1nm; the 102 plane half-width of Comparative Example 1 is 280 arcsec, and the 002 plane half-width is 180 arcsec. It can be seen that the growth method of the epitaxial structure of the application can greatly reduce the dislocation between the epitaxial layer and the substrate and optimize the crystal structure.

[0099] In summary, the application proposes a GaN-based epitaxial structure growth method which can better reduce dislocation, which uses a bottom layer formed by stacking 250-320nm and 140-220nm thick crack-free and low dislocation density AlN+ layer and AlN- layer in a PVD (physical vapor deposition) reaction cavity, instead of the traditional bottom layer of the buffer layer, U-GaN layer and N-type AlGaN layer produced in the MOCVD (metal organic chemical vapor deposition) reaction cavity. The bottom layer formed by the AlN+ layer and the AlN- layer has low dislocation density, the AlN+ layer forms a three-dimensional "island" surface during growth, and the AlN- layer grows in a two-dimensional layer shape. The growth of the two-dimensional layer structure on the three-dimensional "island" surface can reduce the dislocation of the epitaxial structure, reduce stress, and replace the original buffer layer and U-GaN layer. It can also improve the crystal quality and greatly reduce the production cost.

[0100] The above is only an embodiment of the application, and does not limit the patent scope of the application, and any equivalent transformation or direct or indirect application in related technical fields using the content of the application specification and drawings is also included in the patent protection scope of the application.

Claims

1. A GaN-based white light epitaxial structure, characterized by, The P-GaN layer, the multi-quantum layer, the N-GaN layer, the AlN-layer, the AlN+ layer and the sapphire substrate are sequentially arranged from top to bottom; The stress release layer is arranged between the N-GaN layer and the multi-quantum layer; The electron blocking layer is arranged between the multi-quantum layer and the P-GaN layer; The P-type contact layer is arranged on the side of the P-GaN layer away from the multi-quantum layer.

2. A method for growing a GaN-based white light epitaxial structure, the method comprising: The AlN+ layer, the AlN-layer, the N-GaN layer, the multi-quantum layer and the P-GaN layer are sequentially grown on the sapphire substrate; The AlN+ layer is grown in a reaction cavity, the temperature of the reaction cavity is 550-750℃, 20-40sccm argon, 150-240sccm nitrogen and 1-2sccm oxygen are introduced into the reaction cavity, and the duration is 5-10min; The thickness of the AlN+ layer is 250-320nm; The AlN-layer is grown in a reaction cavity, the temperature of the reaction cavity is 600-700℃, 30-70sccm argon, 150-240sccm nitrogen and 1.5-2.5sccm oxygen are introduced into the reaction cavity, and the duration is 3-6min; The thickness of the AlN-layer is 140-220nm; The AlN+ layer, the AlN-layer, the N-GaN layer, the stress release layer, the multi-quantum layer, the electron blocking layer, the P-GaN layer and the P-type contact layer are sequentially grown on the sapphire substrate.

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