GaN-based epitaxial structure, method for manufacturing the same and GaN-based light emitting device

Abstract

This invention provides a GaN-based epitaxial structure and its fabrication method, as well as a GaN-based light-emitting device. The GaN-based epitaxial structure includes a stacked structure disposed on the surface of a patterned sapphire substrate. The stacked structure includes, in sequence, an island-shaped growth region, an island-shaped rapid merging region, a superlattice growth region, and a GaN high-quality region. The island-shaped growth region has a columnar structure, which results in better crystal quality and lower dislocation density. The atomic diffusion length of the island-shaped rapid merging region is greater than that of the island-shaped growth region, which can generate dislocation lines in the island-shaped rapid merging region to release stress. Combined with the superlattice growth region, the dislocation lines bend, tilt, and eventually disappear in the superlattice growth region. This not only obtains an ultrathin GaN-based epitaxial structure but also improves the crystal quality of the GaN-based epitaxial structure.

Description

Technical Field

[0001] This invention relates to the field of optoelectronic technology, and more specifically, to a GaN-based epitaxial structure and its fabrication method, and a GaN-based light-emitting device. Background Technology

[0002] In recent years, III-V group nitrides have been widely used in optoelectronic technology due to their excellent physical and chemical properties, such as large band gap, high breakdown electric field, and high electron saturation mobility. Among these, sapphire substrates, as the most commercially available substrates for GaN-based epitaxial wafers, have significant advantages in terms of material stability and cost. However, the lattice and thermal mismatch between sapphire and GaN materials leads to a high dislocation density during material growth. The presence of dislocations in the epitaxial layer, acting as non-radiative recombination centers and leakage channels, has a significant impact on the performance of GaN-based power electronic and optoelectronic devices. Furthermore, the stress generated by heteroepitaxial growth results in significant warpage of the epitaxial wafer, making the achievement of highly uniform GaN-based epitaxial wafers on sapphire a common challenge in the industry's epitaxial technology field.

[0003] To obtain high-quality GaN materials, in addition to homoepitaxial growth on GaN substrates, various methods such as lateral epitaxial growth and cantilever epitaxial growth have been proposed. Among these, lateral epitaxial growth is widely considered an extremely effective way to reduce dislocation density in heteroepitaxial growth.

[0004] While homoepitaxial growth can avoid the crystal quality degradation caused by lattice mismatch and thermal mismatch, its commercial application is limited due to the scarcity of GaN single crystal materials and the high cost of GaN substrates. In heteroepitaxial growth, lateral epitaxial growth can effectively reduce dislocation line density, but it requires masking techniques, making the process complex and cumbersome. Furthermore, it necessitates a secondary epitaxy, which can easily introduce impurities into the reaction chamber, affecting growth stability and the final device performance. Summary of the Invention

[0005] In view of this, the present invention provides a GaN-based epitaxial structure and its fabrication method, as well as a GaN-based light-emitting device, to solve the problems of lattice mismatch and thermal mismatch caused by heteroepitaxial growth on sapphire substrates in the prior art, which leads to a high dislocation density during material growth; and the fabrication process is too complicated and cumbersome, which easily introduces impurities into the reaction chamber, affecting the growth stability and the final device performance.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A GaN-based epitaxial structure, comprising:

[0008] A patterned sapphire substrate, wherein the surface of the patterned sapphire substrate has a plurality of integrally formed protrusion structures;

[0009] A stacked structure is layered on the surface of the patterned sapphire substrate. The stacked structure includes an island growth region, an island rapid merging region, a superlattice growth region, and a GaN high-quality region that are sequentially stacked along a first direction. The first direction is perpendicular to the patterned sapphire substrate and points from the patterned sapphire substrate to the GaN high-quality region.

[0010] The island-shaped growth region has a columnar structure, and the atomic diffusion length of the island-shaped rapid merging region is greater than the atomic diffusion length of the island-shaped growth region.

[0011] Furthermore, the superlattice growth region includes a first sublayer and a second sublayer with two different lattice constants that are alternately stacked.

[0012] Optionally, the island-shaped growth region includes a high-temperature GaN seed layer, a low-temperature buffer layer, and an island-shaped GaN growth layer stacked sequentially along the first direction, and the high-temperature GaN seed layer, the low-temperature buffer layer, and the island-shaped GaN growth layer are all three-dimensional island structures.

[0013] Optionally, the island-shaped rapid merging region connects to and covers the three-dimensional island structure of the island-shaped GaN growth layer, and the top of the island-shaped GaN growth layer is flush with the top of the protrusion structure.

[0014] Optionally, the island-shaped fast merging region includes a GaN layer, and the thickness of the island-shaped fast merging region ranges from 50 to 1000 nm, including the endpoint values.

[0015] Optionally, the alternating stacking period of the superlattice growth regions is 1-100, and the thickness of the superlattice growth regions ranges from 10-500 nm, including the endpoint values.

[0016] Optionally, the first sub-layer includes A1 X Ga 1-X N layers or In Y Ga 1-Y The N-layer, the second sub-layer including the GaN layer, wherein 0 < x ≤ 1, 0 < y ≤ 1, and the thickness of a single first sub-layer or a single second sub-layer ranges from 1 to 50 nm, including the endpoint values.

[0017] This invention also provides a method for fabricating a GaN-based epitaxial structure, comprising:

[0018] A patterned sapphire substrate is provided, wherein the surface of the patterned sapphire substrate has a plurality of integrally formed protrusion structures;

[0019] A stacked structure is formed on the surface of the patterned sapphire substrate. The stacked structure includes an island growth region, an island rapid merging region, a superlattice growth region and a GaN high quality region formed sequentially along the growth direction. The island growth region includes a high-temperature GaN seed layer, a low-temperature buffer layer and an island GaN growth layer stacked sequentially along the growth direction. The high-temperature GaN seed layer, the low-temperature buffer layer and the island GaN growth layer are all three-dimensional island structures.

[0020] The island-shaped growth region has a columnar structure, and the atomic diffusion length of the island-shaped rapid merging region is greater than the atomic diffusion length of the island-shaped growth region.

[0021] Furthermore, the superlattice growth region includes a first sublayer and a second sublayer with two different lattice constants that are alternately stacked.

[0022] Optionally, the island-shaped GaN growth layer includes lateral growth and longitudinal growth, and the longitudinal growth rate is greater than the lateral growth rate.

[0023] Optionally, the growth temperature and V / III ratio of the island-shaped growth zone are lower than those of the island-shaped rapid merging zone, and the growth pressure of the island-shaped growth zone is higher than that of the island-shaped rapid merging zone.

[0024] Optionally, the V / III ratio of the high-temperature GaN seed layer is greater than that of the low-temperature buffer layer and the island-shaped GaN growth layer.

[0025] Optionally, the method for fabricating the stacked structure includes:

[0026] Step S01: Using an MOCVD device, a high-temperature GaN seed layer is grown on the surface of a patterned sapphire substrate by metal-organic chemical vapor deposition.

[0027] Step S02: Grow a low-temperature buffer layer;

[0028] Step S03: Grow an island-shaped GaN growth layer, wherein the top of the island-shaped GaN growth layer is flush with the top of the protrusion structure;

[0029] Step S04: Growing island-shaped rapid merging regions, wherein the island-shaped rapid merging regions connect to and cover the three-dimensional island structure of the island-shaped GaN growth layer, and the island-shaped rapid merging regions include GaN layers.

[0030] Step S05: Growing a superlattice growth region, wherein the superlattice growth region is alternately stacked with a period of 1-100, and the thickness of the superlattice growth region ranges from 10-500 nm, including the endpoint value;

[0031] The first sublayer includes Al X Ga 1-X N layers or InY Ga 1-Y N layers, the second sub-layer includes a GaN layer, wherein 0 < x ≤ 1, 0 < y ≤ 1, and the thickness of a single first sub-layer or a single second sub-layer ranges from 1 to 50 nm, including the endpoint values;

[0032] Step S06: Grow a high-quality GaN region.

[0033] Optionally, the method for preparing the stacked structure specifically includes the following steps:

[0034] Step A01: Using an MOCVD device, set the growth pressure inside the reaction chamber to 100-500 Torr, the growth temperature to 1000-1100 degrees Celsius, maintain the first V / III ratio inside the reaction chamber, and continuously introduce gallium source and ammonia gas into the reaction chamber for 1-100 seconds. Grow the high-temperature GaN seed layer on the surface of the patterned sapphire substrate. The thickness of the high-temperature GaN seed layer ranges from 1-50 nm, including the endpoint values.

[0035] Step A02: Stop feeding gallium source into the reaction chamber, and set the growth pressure inside the reaction chamber to 200-500 Torr and the growth temperature to 500-800 degrees Celsius.

[0036] Step A03: Maintain the growth pressure inside the reaction chamber at 200-500 Torr, the growth temperature at 500-800 degrees Celsius, set the second V / III ratio inside the reaction chamber, reduce the ammonia flow rate, and continuously introduce gallium source and / or aluminum source into the reaction chamber for 1-500 seconds to grow the low-temperature buffer layer. The thickness of the low-temperature buffer layer is 1-100 nm, including the endpoint value.

[0037] Step A04: Stop feeding gallium and aluminum sources into the reaction chamber, maintain the growth pressure inside the reaction chamber at 200-500 Torr, set the growth temperature inside the reaction chamber at 900-1100 degrees Celsius, and the duration at 10-300 seconds to allow the low-temperature buffer layer to recrystallize.

[0038] Step A05: Maintain the growth pressure inside the reaction chamber at 200-500 Torr and the growth temperature at 900-1100 degrees Celsius. Set the third V / III ratio inside the reaction chamber and continuously introduce gallium source and ammonia into the reaction chamber for 200-2000 seconds until they are flush with the top of the protruding structure. Then stop immediately to grow the island-shaped GaN growth layer.

[0039] Step A06: Set the growth pressure inside the reaction chamber to 100-200 Torr and the growth temperature to 1000-1200 degrees Celsius. Maintain the fourth V / III ratio inside the reaction chamber. Continuously introduce gallium source and ammonia into the reaction chamber for 100-2000 seconds until the three-dimensional island structure of the island GaN growth layer is completely merged. Then immediately stop to form the island rapid merging region. The thickness of the island rapid merging region is in the range of 50-1000 nm, including the endpoint value.

[0040] Step A07: Set the growth pressure inside the reaction chamber to 100-200 Torr and the growth temperature to 900-1100 degrees Celsius. Continuously introduce gallium source, ammonia and aluminum source, or gallium source, ammonia and indium source into the reaction chamber to form the first sublayer. Stop introducing aluminum source or indium source into the reaction chamber to form the second sublayer. Repeat the alternating growth of the first sublayer and the second sublayer to form the superlattice growth region.

[0041] Step A08: Set the growth pressure inside the reaction chamber to 100-200 Torr and the growth temperature to 1000-1200 degrees Celsius. Continuously introduce gallium source and ammonia gas into the reaction chamber to form the high-quality GaN region.

[0042] The present invention also provides a GaN-based light-emitting device, comprising: the GaN-based epitaxial structure described in any one of the preceding claims.

[0043] The above technical solution achieves the following results:

[0044] 1. The GaN-based epitaxial structure provided by this invention comprises a stacked structure disposed on the surface of a patterned sapphire substrate. The stacked structure includes sequentially stacked island growth regions, island rapid merging regions, superlattice growth regions, and GaN high-quality regions. The island growth regions are columnar structures, resulting in better crystal quality and lower dislocation density. The atomic diffusion length of the island rapid merging regions is greater than that of the island growth regions, enabling the generation of dislocation lines in the island rapid merging regions to release stress. Furthermore, the superlattice growth regions include alternating layers of two different lattice constants. The superlattice layers with abrupt interface changes, such as the first and second sublayers, allow dislocation lines extending upward from the island-like rapid merging region to bend, tilt, and eventually disappear within the superlattice growth region. By releasing stress through the dislocation lines generated by the island-like rapid merging region and slowing down the slope of the dislocation lines in conjunction with the superlattice growth region, the thickness of the low-temperature buffer layer can be effectively reduced, resulting in an ultrathin GaN-based epitaxial structure while ensuring the crystal quality of the material. Furthermore, it can suppress dislocation defects, improve crystal quality, and provide a foundation for the subsequent formation of high-quality GaN regions, thereby improving the crystal quality of the GaN-based epitaxial structure.

[0045] 2. Furthermore, by setting up an island-shaped growth region comprising a high-temperature GaN seed layer, a low-temperature buffer layer, and an island-shaped GaN growth layer stacked sequentially, and wherein the high-temperature GaN seed layer, the low-temperature buffer layer, and the island-shaped GaN growth layer are all three-dimensional island structures, the high-temperature GaN seed layer not only provides a seed for the low-temperature buffer layer, which is beneficial for obtaining polycrystalline islands with consistent orientation, but also provides a foundation for the subsequent formation of island-shaped GaN growth layers and island-shaped rapid merging regions. The low-temperature buffer layer can alleviate lattice mismatch and thermal mismatch, reduce crystal defects, and form crystal nuclei with uniform density and consistent orientation, making the island structure size and density of the subsequent island-shaped GaN growth layer more uniform and the crystal orientation more consistent, thereby further improving the crystal quality of the GaN-based epitaxial structure.

[0046] 3. Furthermore, the three-dimensional island structure that connects and covers the island GaN growth layer by setting the top of the island GaN growth layer to be flush with the top of the protrusion structure can avoid crystal orientation disorder when setting the island fast merging region later, thereby further improving the crystal quality of the GaN-based epitaxial structure.

[0047] 4. The method for fabricating GaN-based epitaxial structures provided by this invention can effectively solve the problem of high dislocation density caused by lattice mismatch and thermal mismatch during material growth due to heteroepitaxial growth on sapphire substrates, thereby improving the crystal quality of GaN-based epitaxial structures.

[0048] 5. The GaN-based light-emitting device provided by the present invention can improve the internal quantum efficiency and stability of the GaN-based light-emitting device by using the aforementioned GaN-based epitaxial structure, thereby effectively improving the luminous efficiency and performance of the GaN-based light-emitting device. Attached Figure Description

[0049] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0050] Figure 1 This is a schematic diagram of a GaN-based epitaxial structure provided in an embodiment of the present invention;

[0051] Figures 2.1 to 2.6 The diagram shows the structural schematics corresponding to each step of a method for fabricating a GaN-based epitaxial structure according to an embodiment of the present invention.

[0052] Explanation of symbols in the diagram:

[0053] 1. Patterned sapphire substrate; 11. Protrusion structure; 2. Island growth region; 21. High-temperature GaN seed layer; 22. Low-temperature buffer layer; 23. Island GaN growth layer; 3. Island rapid merging region; 4. Superlattice growth region; 41. First sublayer; 42. Second sublayer; 5. High-quality GaN region. Detailed Implementation

[0054] To make the content of this invention clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0055] Many specific details are set forth in the following description in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0056] Secondly, this application provides a detailed description in conjunction with schematic diagrams. When detailing the embodiments of this application, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not adhering to the usual scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of this application. In addition, actual fabrication should include three-dimensional spatial dimensions of length, width, and depth.

[0057] An embodiment of the present invention provides a GaN-based epitaxial structure, such as... Figure 1 As shown, it includes:

[0058] A patterned sapphire substrate 1 has a number of integrally formed protrusion structures 11 on its surface;

[0059] A stacked structure is stacked on the surface of a patterned sapphire substrate 1. The stacked structure includes an island growth region 2, an island rapid merging region 3, a superlattice growth region 4 and a GaN high-quality region 5 stacked sequentially along a first direction. The first direction is perpendicular to the patterned sapphire substrate 1 and points from the patterned sapphire substrate 1 to the GaN high-quality region 5.

[0060] Among them, the island growth region 2 has a columnar structure, and the atomic diffusion length of the island rapid merging region 3 is greater than that of the island growth region 2.

[0061] Furthermore, the superlattice growth region 4 includes a first sublayer 41 and a second sublayer 42 with two different lattice constants that are alternately stacked.

[0062] It should be noted that, in this embodiment, the material of the superlattice growth region 4 is selected from binary nitride materials and / or ternary nitride materials in the AlInGaN semiconductor material system.

[0063] It should be noted that, in this embodiment, the start layer and end layer of the superlattice growth region 4 are not limited. The start layer of the superlattice growth region 4 can be the first sublayer 41 or the second sublayer 42, and the end layer of the superlattice growth region 4 can be the first sublayer 41 or the second sublayer 42.

[0064] In one embodiment of this application, the protrusion structures 11 are arranged in a periodic manner.

[0065] In one embodiment of this application, the island-shaped fast merging region 3 includes a GaN layer, and the thickness of the island-shaped fast merging region 3 ranges from 50 to 1000 nm, including the endpoint values.

[0066] In one embodiment of this application, the superlattice growth regions 4 are alternately stacked with a period of 1-100, and the thickness of the superlattice growth regions 4 ranges from 10-500 nm, including the endpoint values.

[0067] In one embodiment of this application, the first sublayer 41 includes A1 X Ga 1-X N layers or In Y Ga 1-Y The N-layer and the second sub-layer 42 include a GaN layer, wherein 0 < x ≤ 1 and 0 < y ≤ 1, and the thickness of a single first sub-layer 41 or a single second sub-layer 42 ranges from 1 to 50 nm, including the endpoint values.

[0068] In one embodiment of this application, the top diameter of the protrusion structure 11 is less than or equal to the bottom diameter.

[0069] In one embodiment of this application, the shape of the protrusion structure 11 includes one of the following: conical, pyramidal, hemispherical, ellipsoidal, and elongated.

[0070] To further improve the crystal quality of GaN-based epitaxial structures, optionally, in one embodiment of this application, the following steps are continued: Figure 1 As shown, the island growth region 2 includes a high-temperature GaN seed layer 21, a low-temperature buffer layer 22 and an island GaN growth layer 23 stacked sequentially along the first direction, and the high-temperature GaN seed layer 21, the low-temperature buffer layer 22 and the island GaN growth layer 23 are all three-dimensional island structures.

[0071] In one embodiment of this application, the thickness of the high-temperature GaN seed layer 21 ranges from 1 to 50 nm, including the endpoint values.

[0072] In one embodiment of this application, the thickness of the low-temperature buffer layer 22 ranges from 1 to 100 nm, including the endpoint values.

[0073] In one embodiment of this application, the low-temperature buffer layer 22 includes one or more of AlGaN layers, GaN layers, and AlN layers.

[0074] In one embodiment of this application, the island-shaped rapid merging region 3 connects to and covers the three-dimensional island structure of the island-shaped GaN growth layer 23, and the top of the island-shaped GaN growth layer 23 is flush with the top of the protrusion structure 11.

[0075] This invention also provides a method for fabricating GaN-based epitaxial structures, used to fabricate the GaN-based epitaxial structures of the above embodiments, with reference to... Figure 1 As shown, it includes:

[0076] A patterned sapphire substrate 1 is provided, the surface of which has a plurality of integrally formed protrusion structures 11;

[0077] A stacked structure is formed on the surface of a patterned sapphire substrate 1. The stacked structure includes an island growth region 2, an island rapid merging region 3, a superlattice growth region 4, and a GaN high quality region 5, which are formed sequentially along the growth direction. The island growth region 2 includes a high-temperature GaN seed layer 21, a low-temperature buffer layer 22, and an island GaN growth layer 23, which are stacked sequentially along the growth direction. The high-temperature GaN seed layer 21, the low-temperature buffer layer 22, and the island GaN growth layer 23 are all three-dimensional island structures.

[0078] Among them, the island growth region 2 has a columnar structure, and the atomic diffusion length of the island rapid merging region 3 is greater than that of the island growth region 2.

[0079] Furthermore, the superlattice growth region 4 includes a first sublayer 41 and a second sublayer 42 with two different lattice constants that are alternately stacked.

[0080] It should be noted that, in this embodiment, the material of the superlattice growth region 4 is selected from binary nitride materials and / or ternary nitride materials in the AlInGaN semiconductor material system.

[0081] It should be noted that, in this embodiment, the start layer and end layer of the superlattice growth region 4 are not limited. The start layer of the superlattice growth region 4 can be the first sublayer 41 or the second sublayer 42, and the end layer of the superlattice growth region 4 can be the first sublayer 41 or the second sublayer 42.

[0082] In one embodiment of this application, the island-shaped GaN growth layer 23 includes lateral growth and longitudinal growth, and the longitudinal growth rate is greater than the lateral growth rate.

[0083] It should be noted that in this embodiment, the island growth region 2 is based on the high-temperature GaN seed layer 21. By controlling the growth temperature, growth pressure and V / III ratio, the island GaN growth layer 23 is grown laterally and longitudinally, so that the island growth region 2 forms a columnar structure, which results in better crystal quality and lower dislocation density.

[0084] In one embodiment of this application, the protrusion structures 11 are arranged in a periodic manner.

[0085] In one embodiment of this application, the top diameter of the protrusion structure 11 is less than or equal to the bottom diameter.

[0086] In one embodiment of this application, the shape of the protrusion structure 11 includes one of the following: conical, pyramidal, hemispherical, ellipsoidal, and elongated.

[0087] In one embodiment of this application, the growth temperature and V / III ratio of the island growth region 2 are lower than those of the island rapid merging region 3, and the growth pressure of the island growth region 2 is greater than that of the island rapid merging region 3.

[0088] It should be noted that the V / III ratio represents the ratio of group 5 sources to group 3 sources. Low temperature, low V / III ratio, and high pressure are conducive to the vertical growth of gallium nitride, while high temperature and low pressure can effectively increase the diffusion length of atoms, which is conducive to the lateral growth of gallium nitride. At the same time, at high temperature, in order to balance the high desorption rate of N2 (nitrogen gas), the V / III ratio is increased to avoid the rapid loss of N (nitrogen atoms) from the growth surface to form Ga droplets, which would deteriorate the crystal quality. By controlling the growth temperature, growth pressure, and V / III ratio, the dislocation density of island growth region 2 and island rapid merging region 3 can be reduced, thus improving the crystal quality.

[0089] In one embodiment of this application, the V / III ratio of the high-temperature GaN seed layer 21 is greater than that of the low-temperature buffer layer 22 and the island-shaped GaN growth layer 23.

[0090] In one embodiment of this application, the method for fabricating the stacked structure includes:

[0091] Step S01: Using an MOCVD device, a high-temperature GaN seed layer 21 is grown on the surface of a patterned sapphire substrate 1 by metal-organic chemical vapor deposition.

[0092] Step S02: Grow a low-temperature buffer layer 22, which includes one or more of AlGaN, GaN and AlN layers;

[0093] Step S03: Grow an island-shaped GaN growth layer 23, with the top of the island-shaped GaN growth layer 23 flush with the top of the protrusion structure 11.

[0094] Step S04: Growing island-shaped rapid merging region 3. Island-shaped rapid merging region 3 connects to and covers the three-dimensional island structure of island-shaped GaN growth layer 23. Island-shaped rapid merging region 3 includes GaN layer.

[0095] Step S05: Grow superlattice growth region 4. The superlattice growth region 4 is alternately stacked with a period of 1-100. The thickness of the superlattice growth region 4 ranges from 10-500 nm, including the endpoint values.

[0096] The first sublayer 41 includes Al X Ga 1-X N layers or In Y Ga 1-Y The N-layer, the second sub-layer 42 includes a GaN layer, where 0 < x ≤ 1, 0 < y ≤ 1, and the thickness of a single first sub-layer 41 or a single second sub-layer 42 ranges from 1 to 50 nm, including the endpoint values.

[0097] Step S06: Grow high-quality GaN region 5.

[0098] In one embodiment of this application, the method for fabricating the stacked structure specifically includes the following steps:

[0099] Step A01, as follows Figure 2.1 As shown, an MOCVD device was used, the growth pressure inside the reaction chamber was set to 100-500 Torr, the growth temperature was set to 1000-1100 degrees Celsius, the first V / III ratio was maintained in the reaction chamber, and gallium source and ammonia gas were continuously introduced into the reaction chamber for 1-100s. A high-temperature GaN seed layer 21 was grown on the surface of the patterned sapphire substrate 1. The thickness of the high-temperature GaN seed layer 21 ranged from 1-50nm, including the endpoint value.

[0100] It should be noted that in this embodiment, the high-temperature GaN seed layer 21 can form a randomly distributed three-dimensional island structure under high temperature and N-rich conditions. This not only provides seed crystals for the low-temperature buffer layer 22, which is beneficial for obtaining polycrystalline islands with consistent orientation, but also provides a basis for the subsequent formation of the island-shaped GaN growth layer 23 and the island-shaped rapid merging region 3.

[0101] Step A02: Stop feeding gallium source into the reaction chamber, and set the growth pressure inside the reaction chamber to 200-500 Torr and the growth temperature to 500-800 degrees Celsius.

[0102] Step A03, as follows Figure 2.2As shown, the growth pressure inside the reaction chamber is maintained at 200-500 Torr, the growth temperature is 500-800 degrees Celsius, the second V / III ratio is set in the reaction chamber, the ammonia flow rate is reduced, and gallium source and / or aluminum source are continuously introduced into the reaction chamber for 1-500s to grow a low temperature buffer layer 22. The thickness of the low temperature buffer layer 22 ranges from 1-100nm, including the endpoint value.

[0103] Step A04: Stop feeding gallium and aluminum sources into the reaction chamber, maintain the growth pressure inside the reaction chamber at 200-500 Torr, set the growth temperature inside the reaction chamber at 900-1100 degrees Celsius, and the duration at 10-300s, so that the low temperature buffer layer 22 can recrystallize.

[0104] It should be noted that, in this embodiment, the low-temperature buffer layer 22 is annealed at high temperature after growth, which can alleviate lattice mismatch and thermal mismatch, reduce crystal defects, and form crystal nuclei with uniform density and consistent orientation. This makes the size and density of the three-dimensional island structure of the subsequent island GaN growth layer 23 more uniform and the crystal orientation more consistent.

[0105] Step A05, as follows Figure 2.3 As shown, the growth pressure inside the reaction chamber is maintained at 200-500 Torr, the growth temperature is 900-1100 degrees Celsius, the third V / III ratio is set inside the reaction chamber, and gallium source and ammonia are continuously introduced into the reaction chamber for 200-2000 seconds until they are flush with the top of the protrusion structure 11, and then the process ends immediately to grow an island-shaped GaN growth layer 23.

[0106] It should be noted that in this embodiment, the top of the island-shaped GaN growth layer 23 is flush with the top of the protrusion structure 11; this can prevent the three-dimensional island structure of the island-shaped GaN growth layer 23 from merging too early during the subsequent growth of the island-shaped rapid merging region 3, which would cause crystal orientation disorder.

[0107] Step A06, as follows Figure 2.4 As shown, the growth pressure inside the reaction chamber is set to 100-200 Torr, the growth temperature is set to 1000-1200 degrees Celsius, the fourth V / III ratio is maintained inside the reaction chamber, gallium source and ammonia are continuously introduced into the reaction chamber for 100-2000s, and the process ends immediately after the three-dimensional island structure of the island GaN growth layer 23 is completely merged to form the island rapid merging region 3. The thickness of the island rapid merging region 3 ranges from 50-1000nm, including the endpoint value.

[0108] It should be noted that, in this embodiment, when the top of the island GaN growth layer 23 is flush with the top of the protrusion structure 11, by changing the growth pressure, growth temperature and V / III ratio, longitudinal growth is suppressed and lateral growth of the island rapid merging region 3 is promoted, so that the three-dimensional island structures of the island GaN growth layer 23 merge rapidly and dislocation lines are generated in the island rapid merging region 3 to release stress.

[0109] Step A07, as follows Figure 2.5 As shown, the growth pressure inside the reaction chamber is set to 100-200 Torr, and the growth temperature is set to 900-1100 degrees Celsius. Gallium source, ammonia and aluminum source, or gallium source, ammonia and indium source are continuously introduced into the reaction chamber to form the first sublayer 41. The introduction of aluminum source or indium source into the reaction chamber is stopped to form the second sublayer 42. The alternating growth of the first sublayer 41 and the second sublayer 42 is repeated to form the superlattice growth region 4.

[0110] It should be noted that, in this embodiment, the superlattice growth region 4 includes a first sub-layer 41 and a second sub-layer 42 with two different lattice constants stacked alternately. This superlattice layer with abrupt interface changes can cause the dislocation lines extending upward from the island-shaped rapid merging region 3 to bend, tilt, and eventually disappear in the superlattice layer. By generating dislocation lines through the island-shaped rapid merging region 3 to release stress and combining with the superlattice growth region 4 to slow down the slope of the dislocation lines, it is possible not only to effectively reduce the thickness of the low-temperature buffer layer 22 and obtain an ultra-thin GaN-based epitaxial structure while ensuring the quality of the material crystal, but also to suppress dislocation defects, improve crystal quality, and provide a foundation for the subsequent formation of the GaN high-quality region 5, thereby improving the crystal quality of the GaN-based epitaxial structure.

[0111] Step A08, as follows Figure 2.6 As shown, the growth pressure inside the reaction chamber is set to 100-200 Torr, the growth temperature is set to 1000-1200 degrees Celsius, and gallium source and ammonia gas are continuously introduced into the reaction chamber to form a high-quality GaN region 5.

[0112] It should be noted that in this embodiment, high-purity H2 (hydrogen), high-purity N2 (nitrogen), or a mixture of high-purity H2 and high-purity N2 is used as the carrier gas, trimethylgallium (TMGa) and triethylgallium (TEGa) are used as gallium sources, trimethylindium (TMIn) is used as the indium source, and trimethylaluminum (TMAl) is used as the aluminum source.

[0113] In one embodiment of this application, before forming the stacked structure, the patterned sapphire substrate 1 is placed in the MOCVD reaction chamber, the temperature inside the reaction chamber is set to 1000-1100 degrees Celsius, the chamber pressure is maintained at 100-500 Torr, H2 is introduced, and the chamber is baked at high temperature for 1-10 minutes to remove surface contaminants.

[0114] The present invention also provides a GaN-based light-emitting device, which adopts the GaN stacked structure of the above embodiments.

[0115] In one embodiment of this application, an LED light-emitting structure is stacked on a GaN stacked structure. The LED light-emitting structure is disposed on the surface of the GaN high-quality region 5 away from the superlattice growth region 4. The LED light-emitting structure includes a first type semiconductor layer, an active region, and a second type semiconductor layer stacked sequentially along a first direction.

[0116] It should be noted that the types of the first type semiconductor layer and the second type semiconductor layer in this embodiment are not limited. For example, the first type semiconductor layer can be, but is not limited to, an N-type GaN layer, and correspondingly, the second type semiconductor layer can be, but is not limited to, a P-type GaN layer.

[0117] In another embodiment of this application, a transistor structure is stacked on the GaN stacked structure, and the transistor structure is disposed on the surface of the GaN high-quality region 5 away from the superlattice growth region 4.

[0118] In summary, the above technical solution achieves the following results:

[0119] 1. The GaN-based epitaxial structure provided in this embodiment utilizes a stacked structure disposed on the surface of a patterned sapphire substrate. This stacked structure includes sequentially stacked island growth regions, island rapid merging regions, superlattice growth regions, and GaN high-quality regions. The island growth regions are columnar structures, resulting in better crystal quality and lower dislocation density. The atomic diffusion length of the island rapid merging regions is greater than that of the island growth regions, enabling the generation of dislocation lines to release stress within the island rapid merging regions. Furthermore, the superlattice growth regions include alternating layers of two different lattice constants. The first and second sublayers, with their abrupt interface changes, allow dislocation lines extending upward from the island-like rapid merging region to bend, tilt, and eventually disappear within the superlattice growth region. By releasing stress through the dislocation lines generated by the island-like rapid merging region and mitigating the slope of the dislocation lines in conjunction with the superlattice growth region, the thickness of the low-temperature buffer layer can be effectively reduced. This not only ensures the crystal quality of the material while obtaining an ultrathin GaN-based epitaxial structure, but also suppresses dislocation defects, improves crystal quality, and provides a foundation for the subsequent formation of high-quality GaN regions, thereby enhancing the crystal quality of the GaN-based epitaxial structure.

[0120] 2. Furthermore, by setting up an island-shaped growth region comprising a high-temperature GaN seed layer, a low-temperature buffer layer, and an island-shaped GaN growth layer stacked sequentially, and wherein the high-temperature GaN seed layer, the low-temperature buffer layer, and the island-shaped GaN growth layer are all three-dimensional island structures, the high-temperature GaN seed layer not only provides a seed for the low-temperature buffer layer, which is beneficial for obtaining polycrystalline islands with consistent orientation, but also provides a foundation for the subsequent formation of island-shaped GaN growth layers and island-shaped rapid merging regions. The low-temperature buffer layer can alleviate lattice mismatch and thermal mismatch, reduce crystal defects, and form crystal nuclei with uniform density and consistent orientation, making the island structure size and density of the subsequent island-shaped GaN growth layer more uniform and the crystal orientation more consistent, thereby further improving the crystal quality of the GaN-based epitaxial structure.

[0121] 3. Furthermore, the three-dimensional island structure that connects and covers the island GaN growth layer by setting the top of the island GaN growth layer to be flush with the top of the protrusion structure can avoid crystal orientation disorder when setting the island fast merging region later, thereby further improving the crystal quality of the GaN-based epitaxial structure.

[0122] 4. The GaN-based epitaxial structure fabrication method provided in this embodiment can effectively solve the problem of high dislocation density caused by lattice mismatch and thermal mismatch during material growth due to heteroepitaxial growth on sapphire substrates, thereby improving the crystal quality of GaN-based epitaxial structures.

[0123] 5. The GaN-based light-emitting device provided in this embodiment, by using the aforementioned GaN-based epitaxial structure, can improve the internal quantum efficiency and stability of the GaN-based light-emitting device, thereby effectively improving the luminous efficiency and performance of the GaN-based light-emitting device.

[0124] Those skilled in the art should understand that, in the disclosure of this invention, the terms "lateral", "longitudinal", "upper", "lower", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limiting this invention.

[0125] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0126] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A GaN-based epitaxial structure, characterized in that, include: A patterned sapphire substrate, wherein the surface of the patterned sapphire substrate has a plurality of integrally formed protrusion structures; A stacked structure is layered on the surface of the patterned sapphire substrate. The stacked structure includes an island growth region, an island rapid merging region, a superlattice growth region, and a GaN high-quality region that are sequentially stacked along a first direction. The first direction is perpendicular to the patterned sapphire substrate and points from the patterned sapphire substrate to the GaN high-quality region. The island-shaped growth region has a columnar structure, and the atomic diffusion length of the island-shaped rapid merging region is greater than the atomic diffusion length of the island-shaped growth region. Furthermore, the superlattice growth region includes a first sublayer and a second sublayer with two different lattice constants that are alternately stacked.

2. The GaN-based epitaxial structure according to claim 1, characterized in that: The island-shaped growth region includes a high-temperature GaN seed layer, a low-temperature buffer layer, and an island-shaped GaN growth layer stacked sequentially along the first direction, and the high-temperature GaN seed layer, the low-temperature buffer layer, and the island-shaped GaN growth layer are all three-dimensional island structures.

3. The GaN-based epitaxial structure according to claim 2, characterized in that: The island-shaped rapid merging region connects to and covers the three-dimensional island structure of the island-shaped GaN growth layer, and the top of the island-shaped GaN growth layer is flush with the top of the protruding structure.

4. The GaN-based epitaxial structure according to claim 1, characterized in that: The island-shaped fast merging region includes a GaN layer, and the thickness of the island-shaped fast merging region ranges from 50 to 1000 nm, including the endpoint values.

5. The GaN-based epitaxial structure according to claim 1, characterized in that: The superlattice growth regions are alternately stacked with a period of 1-100, and the thickness of the superlattice growth regions ranges from 10-500 nm, including the endpoint values.

6. The GaN-based epitaxial structure according to claim 1, characterized in that: The first sublayer includes Al X Ga 1-X N layers or In Y Ga 1-Y The N-layer, the second sub-layer including the GaN layer, wherein 0 < x ≤ 1, 0 < y ≤ 1, and the thickness of a single first sub-layer or a single second sub-layer ranges from 1 to 50 nm, including the endpoint values.

7. A method for fabricating a GaN-based epitaxial structure, characterized in that, include: A patterned sapphire substrate is provided, wherein the surface of the patterned sapphire substrate has a plurality of integrally formed protrusion structures; A stacked structure is formed on the surface of the patterned sapphire substrate. The stacked structure includes an island growth region, an island rapid merging region, a superlattice growth region and a GaN high quality region formed sequentially along the growth direction. The island growth region includes a high-temperature GaN seed layer, a low-temperature buffer layer and an island GaN growth layer stacked sequentially along the growth direction. The high-temperature GaN seed layer, the low-temperature buffer layer and the island GaN growth layer are all three-dimensional island structures. The island-shaped growth region has a columnar structure, and the atomic diffusion length of the island-shaped rapid merging region is greater than the atomic diffusion length of the island-shaped growth region. Furthermore, the superlattice growth region includes a first sublayer and a second sublayer with two different lattice constants that are alternately stacked.

8. The method for fabricating a GaN-based epitaxial structure according to claim 7, characterized in that: The island-shaped GaN growth layer includes lateral growth and longitudinal growth, and the longitudinal growth rate is greater than the lateral growth rate.

9. The method for fabricating a GaN-based epitaxial structure according to claim 7, characterized in that: The growth temperature and V / III ratio of the island-shaped growth zone are lower than those of the island-shaped rapid merging zone, while the growth pressure of the island-shaped growth zone is higher than that of the island-shaped rapid merging zone.

10. The method for fabricating a GaN-based epitaxial structure according to claim 7, characterized in that: The V / III ratio of the high-temperature GaN seed layer is greater than that of the low-temperature buffer layer and the island-shaped GaN growth layer.

11. The method for fabricating a GaN-based epitaxial structure according to claim 7, characterized in that: The method for preparing the stacked structure includes: Step S01: Using an MOCVD device, a high-temperature GaN seed layer is grown on the surface of a patterned sapphire substrate by metal-organic chemical vapor deposition. Step S02: Grow a low-temperature buffer layer; Step S03: Grow an island-shaped GaN growth layer, wherein the top of the island-shaped GaN growth layer is flush with the top of the protrusion structure; Step S04: Growing island-shaped rapid merging regions, wherein the island-shaped rapid merging regions connect to and cover the three-dimensional island structure of the island-shaped GaN growth layer, and the island-shaped rapid merging regions include GaN layers; Step S05: Growing a superlattice growth region, wherein the superlattice growth region is alternately stacked with a period of 1-100, and the thickness of the superlattice growth region ranges from 10-500 nm, including the endpoint value; The first sublayer includes Al X Ga 1-X N layers or In Y Ga 1-Y N layers, the second sub-layer includes a GaN layer, wherein 0 < x ≤ 1, 0 < y ≤ 1, and the thickness of a single first sub-layer or a single second sub-layer ranges from 1 to 50 nm, including the endpoint values; Step S06: Grow a high-quality GaN region.

12. The method for fabricating a GaN-based epitaxial structure according to claim 7, characterized in that: The method for preparing the stacked structure specifically includes the following steps: Step A01: Using an MOCVD device, set the growth pressure inside the reaction chamber to 100-500 Torr, the growth temperature to 1000-1100 degrees Celsius, maintain the first V / III ratio inside the reaction chamber, and continuously introduce gallium source and ammonia gas into the reaction chamber for 1-100 seconds. Grow the high-temperature GaN seed layer on the surface of the patterned sapphire substrate. The thickness of the high-temperature GaN seed layer ranges from 1-50 nm, including the endpoint values. Step A02: Stop feeding gallium source into the reaction chamber, and set the growth pressure inside the reaction chamber to 200-500 Torr and the growth temperature to 500-800 degrees Celsius. Step A03: Maintain the growth pressure inside the reaction chamber at 200-500 Torr, the growth temperature at 500-800 degrees Celsius, set the second V / III ratio inside the reaction chamber, reduce the ammonia flow rate, and continuously introduce gallium source and / or aluminum source into the reaction chamber for 1-500 seconds to grow the low-temperature buffer layer. The thickness of the low-temperature buffer layer is 1-100 nm, including the endpoint value. Step A04: Stop feeding gallium and aluminum sources into the reaction chamber, maintain the growth pressure inside the reaction chamber at 200-500 Torr, set the growth temperature inside the reaction chamber at 900-1100 degrees Celsius, and the duration at 10-300 seconds to allow the low-temperature buffer layer to recrystallize. Step A05: Maintain the growth pressure inside the reaction chamber at 200-500 Torr and the growth temperature at 900-1100 degrees Celsius. Set the third V / III ratio inside the reaction chamber and continuously introduce gallium source and ammonia into the reaction chamber for 200-2000 seconds until they are flush with the top of the protruding structure. Then stop immediately to grow the island-shaped GaN growth layer. Step A06: Set the growth pressure inside the reaction chamber to 100-200 Torr and the growth temperature to 1000-1200 degrees Celsius. Maintain the fourth V / III ratio inside the reaction chamber. Continuously introduce gallium source and ammonia into the reaction chamber for 100-2000 seconds until the three-dimensional island structure of the island GaN growth layer is completely merged. Then immediately stop to form the island rapid merging region. The thickness of the island rapid merging region is in the range of 50-1000 nm, including the endpoint value. Step A07: Set the growth pressure inside the reaction chamber to 100-200 Torr and the growth temperature to 900-1100 degrees Celsius. Continuously introduce gallium source, ammonia and aluminum source, or gallium source, ammonia and indium source into the reaction chamber to form the first sublayer. Stop introducing aluminum source or indium source into the reaction chamber to form the second sublayer. Repeat the alternating growth of the first sublayer and the second sublayer to form the superlattice growth region. Step A08: Set the growth pressure inside the reaction chamber to 100-200 Torr and the growth temperature to 1000-1200 degrees Celsius, and continuously introduce gallium source and ammonia gas into the reaction chamber to form the GaN high-quality region.

13. A GaN-based light-emitting device, characterized in that, Includes the GaN-based epitaxial structure according to any one of claims 1 to 6.

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