Nitride-based LED epitaxial structure, its preparation method and application

Abstract

The present invention discloses a nitride-based LED epitaxial structure, its preparation method and application. The epitaxial structure includes an n-type layer, a buffer layer, a restriction layer, a light-emitting layer and a p-type layer; a first inverted cone pit structure is distributed on the surface of the buffer layer; the restriction layer fills the first inverted cone pit structure and is distributed with a second inverted cone pit structure, the light-emitting layer fills the second inverted cone pit structure and is distributed with a third inverted cone pit structure on the surface; the p-type layer fills the third inverted cone pit structure and has a flat surface. The present invention blocks the holes in the light-emitting layer from being transmitted to the nitride buffer layer through the inverted cone pits in the nitride buffer layer by setting a restriction layer, and then introduces new inverted cone pits, thereby increasing the hole distribution density in the light-emitting layer; the holes can use the inverted cone pits to shield carriers from leaking to dislocations, suppressing non-radiative recombination, greatly improving the luminous efficiency of the epitaxial structure, having a simple structure, reducing the preparation cycle, and improving the equipment utilization rate, making it suitable for large-scale mass production processes.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, in particular to the field of optoelectronic device technology, and more particularly to a nitride-based LED epitaxial structure, a preparation method and application thereof. Background Art

[0002] LED devices, such as Micro-LED display devices, have many advantages such as self-luminescence, high efficiency, low power consumption, high integration, and high stability. They are also small in size, highly flexible, and easy to disassemble and merge. They can be applied to any existing display application from small to large sizes. Modern society has entered the information age and is developing towards intelligence. Display is a key link in realizing information exchange and intelligence. Among the many current display technologies, Micro-LED display technology is considered to be a disruptive next-generation display technology.

[0003] Currently, a typical GaN-based LED epitaxial layer consists of an n-type doped layer, a superlattice nitride buffer layer, a multi-quantum well (MQW) light-emitting layer, and a p-type doped layer. Because the concentration of free electrons is higher than that of holes, this can easily lead to uneven distribution of electrons and holes in the MQW (quantum well). Therefore, improving the uniformity of hole distribution in the quantum well light-emitting layer is crucial to the luminous efficiency of the LED epitaxial structure.

[0004] Existing research indicates that inverted cone-shaped pits in quantum well light-emitting layers can effectively promote hole injection, improve the uniformity of carrier distribution in the quantum well light-emitting layer, and thus enhance the luminous efficiency of LED epitaxial structures. However, in actual applications, the hole concentration in the quantum well light-emitting layer is found to be low. Especially for Micro-LED epitaxial structures, the addition of inverted cone-shaped pits in the quantum well light-emitting layer does not theoretically achieve higher luminous efficiency, which seriously restricts the luminous efficiency of Micro-LED epitaxial structures. Summary of the Invention

[0005] In view of the deficiencies in the prior art, the present invention aims to provide a nitride-based LED epitaxial structure, a preparation method and applications thereof.

[0006] To achieve the aforementioned object of the invention, the technical solutions adopted by the present invention include:

[0007] In a first aspect, the present invention provides a nitride-based LED epitaxial structure, comprising an n-type nitride layer, a nitride buffer layer, a nitride confinement layer, a quantum well light-emitting layer, and a p-type nitride layer sequentially arranged along a specified direction;

[0008] Wherein, the nitride buffer layer has a superlattice structure, and a first inverted cone pit structure is distributed on the surface of the nitride buffer layer;

[0009] The nitride restriction layer fills the first inverted cone pit structure, and a second inverted cone pit structure is distributed on the surface of the nitride restriction layer;

[0010] The quantum well light-emitting layer fills at least a portion of the second inverted cone pit structure, and a third inverted cone pit structure is distributed on the surface of the quantum well light-emitting layer;

[0011] The p-type nitride layer fills the third inverted cone pit structure, and the p-type nitride layer has a flat surface.

[0012] Furthermore, the nitride restriction layer includes a nitride capping layer, a nitride opening layer and a nitride barrier layer sequentially arranged along a specified direction; wherein,

[0013] The nitride capping layer fills the first inverted cone pit structure, the nitride opening layer covers the surface of the nitride capping layer and forms the second inverted cone pit structure, and the nitride barrier layer covers the surface of the nitride opening layer;

[0014] The second inverted cone-shaped pit structure extends into the quantum well light-emitting layer to form the third inverted cone-shaped pit structure.

[0015] Furthermore, the surface roughness of the p-type nitride layer is less than 0.3 nm.

[0016] Furthermore, the thickness of the nitride capping layer is 100-300 nm, and the material thereof is aluminum nitride.

[0017] Furthermore, the aluminum-containing nitride includes any one of AlGaN, AlInGaN, and AlN.

[0018] Furthermore, the nitride buffer layer includes periodically stacked superlattice well layers and superlattice barrier layers, and the number of stacking periods of the superlattice well layers and superlattice barrier layers is 2-6;

[0019] The quantum well light-emitting layer includes periodically stacked quantum well layers and quantum barrier layers, and the number of stacking periods of the quantum well layers and quantum barrier layers is 1-8.

[0020] Furthermore, the thickness of the nitride opening layer is 40-80 nm, and the material thereof is any one of GaN, AlGaN and InGaN;

[0021] The opening size of the second inverted cone pit structure formed in the nitride opening layer is greater than 100 nm, and the distribution density is 10 8 -10 11 cm -2 .

[0022] Furthermore, the thickness of the n-type nitride layer is 1-4 μm;

[0023] The thickness of the superlattice well layer is 1-5 nm, and the thickness of the superlattice barrier layer is 10-50 nm;

[0024] The thickness of the nitride capping layer is 100-300 nm, the thickness of the nitride opening layer is 40-80 nm, and the thickness of the nitride barrier layer is 15-40 nm;

[0025] The thickness of the quantum well layer is 1-5 nm, and the thickness of the quantum barrier layer is 6-10 nm;

[0026] The thickness of the p-type nitride layer is 100-200 nm.

[0027] In a second aspect, the present invention further provides a method for preparing the above-mentioned epitaxial structure, comprising:

[0028] 1) forming an n-type nitride layer on a substrate;

[0029] 2) forming a nitride buffer layer on the surface of the n-type nitride layer, and generating a plurality of first inverted cone pit structures in the nitride buffer layer;

[0030] 3) forming a nitride confinement layer on the surface of the nitride buffer layer, wherein the nitride confinement layer fills the first inverted cone pit structure, and forming a second inverted cone pit structure in the nitride confinement layer;

[0031] 4) forming a quantum well light-emitting layer on the surface of the nitride confinement layer, and extending part of the second inverted cone pit structure into the quantum well light-emitting layer to form a third inverted cone pit structure;

[0032] 5) forming a p-type nitride layer on the surface of the quantum well light-emitting layer, wherein the p-type nitride layer fills the third inverted cone pit structure and has a flat surface.

[0033] Furthermore, step 3) growing a nitride confinement layer at a temperature of 950-1050° C. and a pressure of 50-400 Torr specifically includes:

[0034] Under a first pressure, surface treatment is performed on the surface of the nitride buffer layer using at least an In source and an Al source;

[0035] growing an aluminum-containing nitride capping layer using at least an Al source at a second pressure;

[0036] growing a nitride opening layer on the nitride capping layer under a third pressure;

[0037] growing a nitride barrier layer containing In and Al on the nitride opening layer using at least an In source and an Al source;

[0038] The second pressure is lower than the first pressure and the third pressure.

[0039] Furthermore, the surface treatment is performed at elevated temperature for 5-100 seconds, and the first pressure is 100-200 Torr;

[0040] Furthermore, the growth temperature of the nitride capping layer is 1000-1050° C., and the second pressure is 50-100 Torr;

[0041] Furthermore, the growth temperature of the nitride opening layer is 950-1000° C., and the third pressure is 100-200 Torr;

[0042] Furthermore, the growth temperature of the nitride barrier layer is 1000-1050° C., and the pressure during its growth is 150-350 Torr.

[0043] In a third aspect, the present invention further provides a gallium nitride LED device, comprising a first electrode, a second electrode, and the above-mentioned epitaxial structure;

[0044] The first electrode is electrically connected to the n-type nitride layer of the epitaxial structure, and the second electrode is electrically connected to the p-type nitride layer of the epitaxial structure.

[0045] In a fourth aspect, the present invention further provides an LED display unit comprising the above-mentioned nitride-based LED device.

[0046] Based on the above technical solution, compared with the prior art, the beneficial effects of the present invention include at least:

[0047] The nitride-based LED epitaxial structure and preparation method provided by the present invention are as follows: by setting a nitride confinement layer on the nitride buffer layer, first filling the inverted cone pits on the surface of the superlattice, and then introducing new inverted cone pits and extending them to the quantum well light-emitting layer, on the one hand, the first inverted cone pit structure on the surface of the nitride buffer layer can be filled with the nitride covering layer, thereby blocking the holes in the quantum well light-emitting layer from being transmitted to the nitride buffer layer through the inverted cone pits in the nitride buffer layer, avoiding the possibility of holes overflowing the quantum well light-emitting layer, and improving the hole distribution density of the quantum well light-emitting layer; on the other hand, a second inverted cone pit structure is formed on the surface of the nitride opening layer. The cone pit structure and the second inverted cone pit structure extend into the nitride quantum well light-emitting layer to form a third inverted cone pit structure. Holes can use the inverted cone pit to shield carriers from leaking to dislocations, thereby suppressing non-radiative recombination. In addition, the nitride barrier layer can well match the lattice of the quantum well light-emitting layer, reduce the stress of the quantum well light-emitting layer, reduce the quantum confined Stark effect (QCSE), increase the overlap of hole and electron wave functions, and greatly improve the luminescence efficiency of the epitaxial structure. Furthermore, the epitaxial structure provided by the present invention is simple, reduces the preparation cycle of the epitaxial structure, improves the equipment utilization rate, and is suitable for large-scale mass production processes.

[0048] The above description is only an overview of the technical solution of the present invention. In order to enable those skilled in the art to more clearly understand the technical means of this application and implement them according to the contents of the specification, the following is an explanation of the preferred embodiments of the present invention with detailed drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 This is a schematic diagram of the formation principle and structure of an inverted cone pit provided by a typical embodiment of the present invention;

[0050] Figure 2 This is a schematic structural diagram of a nitride-based LED epitaxial structure provided by a typical embodiment of the present invention;

[0051] Figure 3 This is a test chart of the luminous performance of a gallium nitride LED device provided by a typical embodiment of the present invention and a comparative example;

[0052] Figure 4 This is a test chart of the external quantum efficiency of a gallium nitride LED device provided by a typical implementation case and a comparative case of the present invention.

[0053] Explanation of reference numerals: 10, substrate; 11, n-type nitride layer; 12, nitride buffer layer; 13, nitride confinement layer; 14, quantum well light-emitting layer; 15, p-type nitride layer;

[0054] 121. The first inverted cone pit structure; 141. The third inverted cone pit structure. DETAILED DESCRIPTION

[0055] In view of the shortcomings of the prior art, the inventors of this case, after long-term research and extensive practice, have proposed the technical solution of the present invention. The following will further explain this technical solution, its implementation process and principles.

[0056] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0057] Moreover, relational terms such as “first” and “second” are merely used to distinguish one component or method step from another with the same name, but do not necessarily require or imply any actual relationship or order between these components or method steps.

[0058] An embodiment of the present invention provides a nitride-based LED epitaxial structure, comprising an n-type nitride layer, a nitride buffer layer, a nitride confinement layer, a quantum well light-emitting layer, and a p-type nitride layer, which are sequentially arranged along a specified direction; wherein the nitride buffer layer has a superlattice structure, and a first inverted cone pit structure is distributed on the surface of the nitride buffer layer; the nitride confinement layer fills the first inverted cone pit structure, and a second inverted cone pit structure is distributed on the surface of the nitride confinement layer; the quantum well light-emitting layer fills at least a portion of the second inverted cone pit structure, and a third inverted cone pit structure is distributed on the surface of the quantum well light-emitting layer; the p-type nitride layer fills the third inverted cone pit structure, and the p-type nitride layer has a flat surface.

[0059] The embodiment of the present invention further provides a method for preparing a nitride-based LED epitaxial structure, comprising the following steps:

[0060] 1) An n-type nitride layer is formed on a substrate.

[0061] 2) forming a nitride buffer layer on the surface of the n-type nitride layer, and generating a plurality of first inverted cone pit structures in the nitride buffer layer.

[0062] 3) forming a nitride confinement layer on the surface of the nitride buffer layer, wherein the nitride confinement layer fills the first inverted cone-shaped pit structure, and forming a second inverted cone-shaped pit structure in the nitride confinement layer.

[0063] 4) forming a quantum well light-emitting layer on the surface of the nitride confinement layer, and extending a portion of the second inverted cone pit structure into the quantum well light-emitting layer to form a third inverted cone pit structure.

[0064] 5) forming a p-type nitride layer on the surface of the quantum well light-emitting layer, wherein the p-type nitride layer fills the third inverted cone pit structure and has a flat surface.

[0065] The nitride-based LED epitaxial structure may be a Micro-LED or a common LED structure.

[0066] For details, see Figure 1-Figure 2 Some embodiments of the present invention exemplarily provide a Micro-LED epitaxial structure, which may include at least a substrate 10 and an n-type nitride layer (as the n-type nitride layer 11, the same below), a nitride buffer layer 12, a nitride confinement layer 13, a nitride quantum well light-emitting layer 14 and the p-type nitride layer 15, wherein the surface of the nitride buffer layer 12 has a first inverted cone pit structure 12l, and the nitride confinement layer 13 includes a nitride capping layer, a nitride opening layer and a nitride barrier layer, wherein the nitride capping layer is filled with a nitride buffer layer. The surface of the layer 12 has a first inverted cone pit structure 121 and has a flat surface, the surface of the nitride opening layer has a second inverted cone pit structure (not shown in the figure), the nitride barrier layer fills part of the second inverted cone pit structure on the surface of the nitride opening layer and has an extended inverted cone pit structure, the quantum well light-emitting layer 14 fills part of the inverted cone pit structure on the surface of the nitride barrier layer and has a third inverted cone pit structure 141 that continues to extend and grow from the extended inverted cone pit structure, and the p-type nitride layer 15 fills the third inverted cone pit structure 141 on the quantum well light-emitting layer 14 and has a flat surface.

[0067] At the same time, some embodiments of the present invention exemplarily provide a process for preparing the above-mentioned epitaxial structure, and the specific process can be as follows:

[0068] S1. Providing a substrate 10. Growing an n-type nitride layer 11 with a thickness of 1-4 μm on the substrate 10 at a temperature of 1050-1200° C. and a pressure of 100-400 Torr.

[0069] S2. A nitride buffer layer 12 is grown on the n-type nitride layer 11 at a temperature of 850-950°C and a pressure of 150-350 Torr. The nitride buffer layer 12 includes a nitride superlattice well layer with a thickness of 1-5 nm and a nitride superlattice barrier layer with a thickness of 10-50 nm, which are grown in a periodic cycle of 2-6 times.

[0070] S3, growing a nitride confinement layer 13 on the nitride buffer layer 12 at a temperature of 950-1050° C. and a pressure of 100-400 Torr, comprising at least the following sub-steps:

[0071] S31, in the pressure range of 100-200torr, while heating, introduce In source and Al source at the same time, and maintain for 5-100s. In this step, considering that the surface activity of Al atoms is poor, it is necessary to improve the migration and distribution uniformity of Al atoms on the surface of the nitride buffer layer 12 at a higher temperature, and considering that under high temperature (for example, >1000°C), the decomposition efficiency of the In source increases exponentially, and the residence time on the surface of the nitride buffer layer 12 decreases exponentially, affecting the surface activity of the In atoms, so step S31 adopts the method of heating while introducing In source and Al source, while ensuring the migration ability of Al atoms and the surface activity of In atoms. At the same time, the introduction during the heating process makes the Al atoms distributed at different positions on the surface of the nitride buffer layer 12 have different potential energies. Al atoms with different potential energies can form the best surface uniformity distribution by using different annealing degrees in the process of temperature gradient equivalent to annealing.

[0072] S32. The temperature is raised to a range of 1000-1050°C. The In source is turned off, and the Al source is continuously introduced to grow an aluminum-containing nitride capping layer with a thickness of 100-300nm at a pressure range of 50-100 torr. The principle that this capping layer can cover the first inverted cone pit structure and form a relatively flat surface is: 1. Covering by sufficient thickness and / or 2. Covering is achieved by controlling the process conditions in this step: In step S32, the Al source has low mobility and can fill the first inverted cone pit structure; and the lower pressure in this step compared to the previous and next steps can reduce the pre-reaction of the In and Al sources, avoiding the reduction in filling effect caused by the pre-reaction, especially the generation of particle byproducts of Al. In this step, the aluminum-containing nitride capping layer formed can be: AlGaN, AlInGaN, or AlN.

[0073] S33. The temperature is lowered to the range of 950-1000°C, and a nitride opening layer with a thickness of 40-80nm is grown on the nitride covering layer at a pressure range of 100-200torr. In this step, a low-pressure control process is used to form the nitride opening layer: under low pressure, the impurity atoms (such as C and / or O) in the nitride opening layer can form regional high doping, and the highly doped impurity atoms provide a base point for the formation of the opening, thereby forming the second inverted cone pit structure. Among them, the material of the nitride opening layer can be preferably GaN, or AlGaN, InGaN. The opening on the surface of the nitride opening layer (i.e., the second inverted cone pit structure) is not less than 100-200nm, and the distribution density is preferably between 10 8 -10 11 cm -2 within the range.

[0074] S34, raising the temperature to the range of 1000-1050°C, introducing an In source and an Al source, and growing a 15-40nm thick nitride barrier layer containing In and Al on the nitride opening layer at a pressure range of 150-350 Torr.

[0075] S4. Growing a quantum well light-emitting layer 14 on the nitride confinement layer 13 at a temperature of 700-1000° C. and a pressure of 200-400 Torr, including a quantum well layer with a thickness of 1-5 nm and a GaN quantum barrier layer with a thickness of 6-10 nm, which are grown periodically for 1-8 times.

[0076] S5. Growing a p-type nitride layer 15 with a thickness of 100-200 nm on the nitride quantum well light-emitting layer 14 at a temperature of 950-1050° C. and a pressure of 100-600 Torr.

[0077] Moreover, since the third inverted cone pit structure 141 in the quantum well light-emitting layer 14 is formed by extending the second inverted cone pit structure present in the nitride confinement layer 13, most of its apex is located on the nitride opening layer. Therefore, the third inverted cone pit structure 141 has a very uniform depth, which also brings about a very uniform hole injection depth, thereby bringing about more stable and controllable light emission.

[0078] Specifically, the nitride capping layer may fill the first cone pit structure on the surface of the nitride buffer layer 12 .

[0079] Specifically, a second inverted cone pit structure with an opening size of not less than 100-200 nm may be formed on the surface of the nitride opening layer.

[0080] Specifically, an extended inverted cone pit structure with an opening size of no less than 100-200 nm may be formed on the surface of the nitride barrier layer.

[0081] Specifically, a third inverted cone pit structure 141 with an opening size of not less than 100-200 nm may be formed on the surface of the quantum well light-emitting layer 14 .

[0082] Specifically, the p-type nitride layer 15 can fill the inverted cone pit structure 141 of the quantum well light-emitting layer 14 to form a flat surface with a roughness of less than 0.3 nm.

[0083] It should be noted that in the embodiment of the present invention, the Micro-LED epitaxial structure is realized by MOCVD epitaxial growth, and the precursor source, gas source and carrier gas required for growth can be various common precursor sources, gas sources and carrier gases required for MOCVD epitaxial growth, including Ga source, Al source, In source, Mg, Si source and N source and N2, H2, Ar, etc. The optional range of Ga source in the present invention can be, for example, trimethylgallium (TMG) and triethylgallium (TEG), the Al source can be trimethylaluminum (TMAl), the In source can be trimethylindium (TMIn), the Mg source can be bismuthocene magnesium (Cp2Mg), the Si source can be silane (SiH4), the N source can be ammonia (NH3), and the carrier gas can be N2 and H2, but of course it is not limited to this.

[0084] The technical solution of the present invention is further described in detail below through several more specific embodiments. However, it should be noted that the selected embodiments are only used to illustrate the present invention, to facilitate those skilled in the art to refer to or repeatedly implement or deeply understand the technical solution of the present invention, and do not limit the scope of the present invention.

[0085] Example 1

[0086] This embodiment illustrates a preparation process of a Micro-LED epitaxial structure, as shown below:

[0087] S1. Provide a substrate 10.

[0088] S2 . Growing an n-type GaN layer with a thickness of 3 μm on the substrate 10 at a temperature of 1105° C. and a pressure of 200 torr to serve as the n-type nitride layer 11 .

[0089] S3. Growing a nitride buffer layer 12 on the n-type nitride layer 11 at a temperature of 860° C. and a pressure of 200 Torr, including a 2 nm thick InGaN superlattice well layer and a 40 nm thick GaN superlattice barrier layer grown periodically for 5 times.

[0090] In step S3, the nitride buffer layer 12 can, on the one hand, play the role of electron buffering and stress control, improving the carrier distribution uniformity and stress in the nitride quantum well light-emitting layer; on the other hand, the larger inverted cone pit structure in the quantum well light-emitting layer usually originates from the nitride buffer layer 12. However, the inventors of the present invention have found through research that in the existing epitaxial structure, there is a luminescence phenomenon in the nitride buffer layer 12. The reason is that, in the existing epitaxial structure, holes can enter the nitride buffer layer 12 through the inverted cone pit structure, causing hole leakage, thereby leading to luminescence. This phenomenon reduces the hole distribution density in the quantum well light-emitting layer 14.

[0091] Therefore, in the present invention, the inventor creatively adds a nitride confinement layer 13 on the nitride buffer layer 12 to solve the above problem.

[0092] S4, growing a nitride confinement layer 13 on the nitride buffer layer, comprising at least the following steps:

[0093] S41. Under a pressure of 125 torr, introduce In source and Al source simultaneously while heating to 1020°C and maintain for 65 seconds.

[0094] S42. The temperature is raised to 1020°C, the In source is turned off, and the Al source is continuously introduced to grow an AlGaN nitride capping layer with a thickness of 150 nm at a pressure of 75 Torr.

[0095] S43 , lowering the temperature to within the range of 970° C., and growing a GaN nitride opening layer with a thickness of 60 nm on the AlGaN nitride cap layer under a pressure of 150 Torr.

[0096] S44, raising the temperature to 1025°C, introducing an In source and an Al source, and growing a 30nm AlInGaN-containing nitride barrier layer on the nitride opening layer under a pressure of 250 Torr.

[0097] S5. On the nitride buffer layer, a quantum well light-emitting layer 14 is grown at a pressure of 300 torr, including an InGaN quantum well layer with a thickness of 1-5 nm grown at a temperature of 760°C and a GaN quantum barrier layer with a thickness of 8 nm grown at a temperature of 820°C, which are periodically cycled twice.

[0098] S6. Growing a p-type nitride layer 15 with a thickness of 150 nm on the nitride quantum well light-emitting layer 14 at a temperature of 1015° C. and a pressure of 400 torr.

[0099] The luminous performance test diagram of the LED device prepared using the above epitaxial structure is shown in the figure Figure 3 shown.

[0100] Example 2

[0101] This embodiment illustrates a preparation process of a Micro-LED epitaxial structure, which is substantially the same as that of Example 1, except that:

[0102] In step S44 , a 15 nm thick nitride barrier layer containing AlInGaN is grown.

[0103] Example 3

[0104] This embodiment illustrates a preparation process of a Micro-LED epitaxial structure, which is substantially the same as that of Example 1, except that:

[0105] In step S44 , a 40 nm thick nitride barrier layer containing AlInGaN is grown.

[0106] After testing and analysis, it was found that for the LED devices prepared using the same process in Examples 1, 2, and 3, when the operating current increased from 20 mA to 1000 mA, the corresponding luminous efficiency decreased by 46.2%, 40.5%, and 38.2%, respectively. That is, the AlInGaN nitride barrier layer has a relatively large impact on the efficiency attenuation of the LED device. In actual work, the thickness of the AlInGaN nitride barrier layer can be adjusted according to the size requirements of the LED device.

[0107] Example 4

[0108] This embodiment illustrates a preparation process of a Micro-LED epitaxial structure, which is substantially the same as that of Example 1, except that:

[0109] The thickness of the AlGaN cap layer grown in step S42 is 100 nm.

[0110] Example 5

[0111] This embodiment illustrates a preparation process of a Micro-LED epitaxial structure, which is substantially the same as that of Example 1, except that:

[0112] The thickness of the AlGaN cap layer grown in step S42 is 300 nm.

[0113] After testing and analysis, it was found that the LED devices prepared using the same process in Examples 1, 4, and 5 had ESD yields of 97%, 95%, and 99%, respectively, under a reverse voltage of 2 kV. This means that the AlGaN capping layer has a significant impact on the ESD performance of the LED device. However, as the thickness of the AlGaN capping layer increases from 100 nm to 300 nm, the voltage of the LED device increases by 0.03 V at an operating current of 20 mA. Therefore, adaptive selection is required based on actual product requirements.

[0114] Comparative Example 1

[0115] This comparative example illustrates a preparation process of a Micro-LED epitaxial structure, which is substantially the same as that of Example 1, with the following differences:

[0116] The steps of forming a nitride capping layer, a nitride opening layer and a nitride barrier layer are omitted, that is, the nitride conical ...

[0117] The luminous performance test diagram of the LED device prepared using the above epitaxial structure is shown in the figure Figure 3 As shown, the quantum efficiency of Example 1 and Comparative Example 1 is compared. Figure 4 shown.

[0118] Comparative Example 2

[0119] This comparative example illustrates a preparation process of a Micro-LED epitaxial structure, which is substantially the same as that of Example 1, with the following differences:

[0120] The LED device prepared by the same process without setting the nitride opening layer cannot obtain sufficient third inverted cone pit structure formed by extending the second inverted cone pit structure in the formed quantum well light-emitting layer 14 because the nitride opening layer is not set. The device brightness of the device at an operating current of 20 mA is more than 25% lower than that of Example 1. This also proves that the third inverted cone pit structure extended in the quantum well light-emitting layer 14 can effectively promote hole injection, and can be used to improve the uniformity of carrier distribution in the quantum well light-emitting layer and improve the brightness of the LED device. That is, if the third inverted cone pit structure is not set in the quantum well light-emitting layer 14, there will be a great disadvantage in brightness performance.

[0121] Example 6

[0122] This embodiment illustrates a preparation process of a Micro-LED epitaxial structure, which is substantially the same as that of Example 1, with the only difference being the process conditions in step S4:

[0123] S41. Under a pressure of 100 torr, introduce In source and Al source simultaneously while heating to 1000°C and maintain for 100 seconds.

[0124] S42. The temperature is raised to 1000° C., the In source is turned off, and the Al source is continuously introduced to grow an AlGaN nitride capping layer with a thickness of 100 nm at a pressure of 50 Torr.

[0125] S43 , lowering the temperature to within the range of 950° C., and growing a GaN nitride opening layer with a thickness of 40 nm on the AlGaN nitride cap layer under a pressure of 100 Torr.

[0126] S44 , raising the temperature to 1050° C., introducing an In source and an Al source, and growing a 15 nm AlInGaN nitride barrier layer on the nitride opening layer under a pressure of 150 Torr.

[0127] Example 7

[0128] This embodiment illustrates a preparation process of a Micro-LED epitaxial structure, which is substantially the same as that of Example 1, with the only difference being the process conditions in step S4:

[0129] S41. Under a pressure of 200 torr, introduce In source and Al source simultaneously while heating to 1050°C and maintain for 5 seconds.

[0130] S42. The temperature is raised to 1050° C., the In source is turned off, and the Al source is continuously introduced to grow an AlGaN nitride capping layer with a thickness of 300 nm at a pressure of 100 Torr.

[0131] S43 , lowering the temperature to within the range of 1000° C., and growing a GaN nitride opening layer with a thickness of 80 nm on the AlGaN nitride cap layer under a pressure of 200 Torr.

[0132] S44, maintaining the temperature at 1000°C, introducing an In source and an Al source, and growing a 40nm AlInGaN nitride barrier layer on the nitride opening layer under a pressure of 350 Torr.

[0133] Example 8

[0134] This embodiment illustrates a preparation process of a Micro-LED epitaxial structure, which is substantially the same as that of Embodiment 1, except that the material of the nitride capping layer formed in step S42 is AlN.

[0135] Example 9

[0136] This embodiment illustrates a preparation process of a Micro-LED epitaxial structure, which is substantially the same as that of Embodiment 1, except that in step S42 , the introduction of the In source is not stopped, and the material of the formed nitride capping layer is AlInGaN.

[0137] Based on the same test method as above, it was found that the device structures formed in Examples 6-9 all had relatively close luminous efficiencies and similar ESD performances under the same current.

[0138] Based on the above embodiments and comparative examples, it can be clearly seen that the nitride-based LED epitaxial structure, the preparation method thereof, and the gallium nitride LED device provided in the embodiments of the present invention are provided by setting a nitride confinement layer 13 on the nitride buffer layer 12, first filling the inverted cone pits on the surface of the superlattice, and then introducing the inverted cone pits and extending them to the quantum well light-emitting layer 14. On the one hand, the nitride covering layer can be used to fill the inverted cone pits on the surface of the nitride buffer layer 12, thereby blocking the holes in the quantum well light-emitting layer 14 from being transmitted to the nitride buffer layer 12 through the inverted cone pits in the nitride buffer layer 12, thereby avoiding the possibility of holes overflowing the quantum well light-emitting layer 14, and improving the quantum well light-emitting layer 14. 4; on the other hand, an inverted cone pit is formed on the surface of the nitride opening layer, and the inverted cone pit extends to the nitride quantum well light-emitting layer 14. Holes can use the inverted cone pit to shield carriers from leaking to dislocations, thereby suppressing non-radiative recombination; in addition, the nitride barrier layer can well match the lattice of the quantum well light-emitting layer 14, reduce the stress of the quantum well light-emitting layer 14, reduce the quantum confined Stark effect (QCSE), increase the overlap of hole and electron wave functions, and greatly improve the luminescence efficiency of the epitaxial structure; furthermore, the epitaxial structure provided by the present invention is simple, reduces the preparation cycle of the epitaxial structure, improves the equipment utilization rate, and is suitable for large-scale mass production processes.

[0139] It should be understood that the above embodiments are merely illustrative of the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent variations or modifications made in accordance with the spirit and substance of the present invention are intended to be encompassed within the scope of protection of the present invention.

Claims

1. A nitride-based LED epitaxial structure, characterized in that It includes an n-type nitride layer, a nitride buffer layer, a nitride confinement layer, a quantum well light-emitting layer and a p-type nitride layer which are sequentially arranged along a specified direction; Wherein, the nitride buffer layer has a superlattice structure, and a first inverted cone pit structure is distributed on the surface of the nitride buffer layer; The nitride restriction layer includes a nitride capping layer, a nitride opening layer, and a nitride barrier layer sequentially arranged along a specified direction; wherein the nitride capping layer fills the first inverted cone pit structure and has a flat surface; the nitride opening layer covers the surface of the nitride capping layer and forms a second inverted cone pit structure; and the nitride barrier layer covers the surface of the nitride opening layer; The quantum well light-emitting layer fills at least a portion of the second inverted cone pit structure, and the second inverted cone pit structure extends into the quantum well light-emitting layer to form a third inverted cone pit structure; The p-type nitride layer fills the third inverted cone pit structure, and the p-type nitride layer has a flat surface.

2. The epitaxial structure according to claim 1, wherein: The surface roughness of the p-type nitride layer is less than 0.3 nm.

3. The epitaxial structure according to claim 1, wherein: The thickness of the nitride capping layer is 100-300 nm, and the material thereof is aluminum nitride.

4. The epitaxial structure according to claim 3, wherein: The thickness of the nitride opening layer is 40-80 nm, and the material thereof is any one of GaN, AlGaN and InGaN; The opening size of the second inverted cone pit structure formed in the nitride opening layer is greater than 100 nm, and the distribution density is 10 8 -10 11 cm -2 .

5. A method for preparing a nitride-based LED epitaxial structure according to any one of claims 1 to 4, characterized in that: include: 1) forming an n-type nitride layer on a substrate; 2) forming a nitride buffer layer on the surface of the n-type nitride layer, and generating a plurality of first inverted cone pit structures in the nitride buffer layer; 3) forming a nitride confinement layer on the surface of the nitride buffer layer, wherein the nitride confinement layer fills the first inverted cone pit structure and forms a second inverted cone pit structure in the nitride confinement layer; 4) forming a quantum well light-emitting layer on the surface of the nitride confinement layer, and extending part of the second inverted cone pit structure into the quantum well light-emitting layer to form a third inverted cone pit structure; 5) forming a p-type nitride layer on the surface of the quantum well light-emitting layer, wherein the p-type nitride layer fills the third inverted cone pit structure and has a flat surface.

6. The preparation method according to claim 5, characterized in that Step 3) growing a nitride confinement layer at a temperature of 950-1050°C and a pressure of 50-400 torr, specifically comprising: Under a first pressure, surface treatment is performed on the surface of the nitride buffer layer using at least an In source and an Al source; growing an aluminum-containing nitride capping layer using at least an Al source at a second pressure; growing a nitride opening layer on the nitride capping layer under a third pressure; growing a nitride barrier layer containing In and Al on the nitride opening layer using at least an In source and an Al source; The second pressure is lower than the first pressure and the third pressure.

7. The preparation method according to claim 6, characterized in that The surface treatment is performed at elevated temperature for 5-100 seconds, and the first pressure is 100-200 Torr; and / or, the growth temperature of the nitride capping layer is 1000-1050° C., and the second pressure is 50-100 Torr; And / or, the growth temperature of the nitride opening layer is 950-1000° C., and the third pressure is 100-200 Torr; And / or, the growth temperature of the nitride barrier layer is 1000-1050° C., and the pressure during its growth is 150-350 Torr.

8. A nitride-based LED device, characterized in that: comprising a first electrode, a second electrode, and the nitride-based LED epitaxial structure according to any one of claims 1 to 4; The first electrode is electrically connected to the n-type nitride layer of the nitride-based LED epitaxial structure, and the second electrode is electrically connected to the p-type nitride layer of the nitride-based LED epitaxial structure.

9. An LED display unit, characterized in that The nitride-based LED device according to claim 8 is included.

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