Light-emitting diode structure based on a graphitized nitride single-crystal substrate and preparation method thereof

Abstract

The present application discloses a light-emitting diode structure based on a patterned nitride single-crystal substrate and a preparation method thereof. The light-emitting diode structure includes a nitride single-crystal substrate, a nitride layer, a planarization layer, and a light-emitting epitaxial layer; a plurality of regular pattern structures are formed on the surface of the substrate, and the pattern structures protrude or recess relative to the surface of the nitride single-crystal substrate; the nitride layer continuously conformally covers the plurality of pattern structures, and the two cooperate to form a reflection structure, and the reflection structure can at least reflect the light emitted by the light-emitting epitaxial layer; the surface of the planarization layer is flat and continuously covers the nitride layer; the light-emitting epitaxial layer is grown on the planarization layer. The light-emitting diode structure of the present application has the advantages of low leakage current, long service life, high light extraction efficiency, and high light emission uniformity, etc., can realize high-brightness and high-efficiency LED devices, and has good application prospects in high-end application fields.

Description

Technical Field

[0001] The present application relates to a light-emitting diode structure (LED), and particularly to a light-emitting diode structure based on a patterned nitride single crystal substrate and a preparation method thereof, belonging to the field of semiconductor technology. Background Art

[0002] GaN-based LEDs based on a patterned sapphire substrate (PSS) have been widely used at present due to characteristics such as high brightness. By adopting a patterned sapphire substrate, on the one hand, the growth mode of GaN material on it can be changed from vertical epitaxy to lateral epitaxy, so as to effectively reduce the dislocation density of the GaN epitaxial material, further reduce the non-radiative recombination in the active region, reduce the reverse leakage current, and improve the lifespan of the LED; on the other hand, the light emitted from the active region can be scattered multiple times by the interface between the GaN epitaxial material and the sapphire substrate, changing the exit angle of the total reflection light, increasing the probability of the light of the flip-chip LED exiting from the sapphire substrate, thereby improving the light extraction efficiency and significantly increasing the brightness of the emitted light of the LED.

[0003] In recent years, GaN single crystal substrates have been favored by the industry due to their advantages such as ultra-low dislocation density and ultra-high crystal quality. Growing GaN material on a GaN single crystal substrate belongs to homoepitaxy, and very high-quality LED epitaxial crystals can be obtained. However, at the same time, there is no interface formation reflection in the LED, and there is no multi-angle reflection to improve the light extraction efficiency, resulting in the light extraction efficiency of GaN homoepitaxial LEDs being inferior to that of LEDs grown on a patterned sapphire substrate. Summary of the Invention

[0004] The main purpose of the present application is to provide a light-emitting diode structure based on a patterned nitride single crystal substrate and a preparation method thereof to overcome the deficiencies in the prior art.

[0005] To achieve the foregoing invention purpose, the technical solutions adopted in the present application include:

[0006] One aspect of the present application provides a light-emitting diode structure based on a patterned nitride single crystal substrate, which is characterized by comprising:

[0007] A nitride single crystal substrate, on the surface of which a plurality of regular pattern structures are formed, and the pattern structures protrude or are recessed relative to the surface of the nitride single crystal substrate;

[0008] A nitride layer, continuously conformally covering the plurality of pattern structures and cooperating with the plurality of pattern structures to form a reflection structure, and the reflection structure can at least reflect the light emitted by the light-emitting epitaxial layer;

[0009] A planarization layer, continuously covering the nitride layer, and the surface of the planarization layer is flat; and

[0010] A light-emitting epitaxial layer, grown on the planarization layer.

[0011] Another aspect of the present application provides a method for manufacturing a light-emitting diode structure based on a patterned nitride single-crystal substrate, which includes:

[0012] Processing a plurality of regular pattern structures on the surface of the nitride single-crystal substrate, the pattern structures protruding or recessing relative to the surface of the nitride single-crystal substrate;

[0013] Forming a nitride layer on the plurality of pattern structures, and making the nitride layer continuously conformally cover the plurality of pattern structures, and making the nitride layer also cooperate with the plurality of pattern structures to form a reflection structure, the reflection structure being capable of at least reflecting the light emitted by the light-emitting epitaxial layer;

[0014] Growing a planarization layer with a flat surface on the nitride layer; and

[0015] Growing a light-emitting epitaxial layer on the planarization layer.

[0016] By forming a plurality of regular pattern structures on the surface of the nitride single-crystal substrate in the present application, it can be used as an interface layer between the nitride single-crystal substrate and the nitride material, so that the light emitted from the active region is scattered multiple times by the interface layer, changing the exit angle of the total reflection light and improving the light extraction efficiency; at the same time, growing a nitride layer on the graphic structure, especially an Al-containing nitride layer, can make the pattern structure and the nitride layer cooperate to form a larger-area and better-continuous light reflection interface, more efficiently reflect the light emitted by the light-emitting epitaxial layer, significantly improve the light extraction efficiency of the device, and at the same time, the nitride layer can be used to block and suppress the dislocations of the nitride single-crystal substrate, further improving the quality of the epitaxial crystal; then, by growing a planarization layer, a flat GaN material layer can be formed, and a high-brightness homogeneous nitride LED can be realized.

[0017] Compared with the prior art, the technical solution of the present application not only gives full play to the advantages of homoepitaxy, enables the epitaxial structure of the light-emitting diode to have ultra-high crystal quality, and ensures that the light-emitting diode has characteristics such as low leakage current and long life, but also significantly improves the light extraction efficiency and light emission uniformity of the light-emitting diode, realizes a high-brightness and high-efficiency light-emitting diode device, and has good application prospects in high-end application fields. Description of the Drawings

[0018] To more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0019] Figure 1 It is a schematic diagram of a light-emitting diode structure based on a patterned nitride single-crystal substrate in the first embodiment of the present application;

[0020] Figure 2 is Figure 1 a partial enlarged schematic diagram of part A in

[0021] Figure 3 It is a schematic process flow diagram of the preparation of a light-emitting diode structure based on a patterned nitride single-crystal substrate in the present application;

[0022] Figure 4 It is a schematic diagram of a light-emitting diode structure based on a patterned nitride single-crystal substrate in the second embodiment of the present application;

[0023] Figure 5 is Figure 4 a partial enlarged schematic diagram of part B in Detailed implementation manners

[0024] As mentioned above, LEDs formed by homoepitaxy using a GaN single-crystal substrate are often inferior to those based on a patterned sapphire substrate in terms of light extraction efficiency and the like. And some existing solutions for increasing the light extraction efficiency of GaN homoepitaxial LEDs all have more or less some defects. In view of this, after a large number of studies and experiments, the applicant of the present application has been able to propose the technical solutions of the present application, which will be described in more detail below.

[0025] A light-emitting diode structure based on a patterned nitride single-crystal substrate provided by some embodiments of the present application includes:

[0026] A nitride single-crystal substrate, on the surface of which a plurality of regular pattern structures are formed, and the pattern structures protrude or are recessed relative to the surface of the nitride single-crystal substrate;

[0027] A nitride layer, continuously conformally covering the plurality of pattern structures and cooperating with the plurality of pattern structures to form a reflection structure, and the reflection structure can at least reflect the light emitted by the light-emitting epitaxial layer;

[0028] A planarization layer, continuously covering the nitride layer, and the surface of the planarization layer is flat; and

[0029] A light-emitting epitaxial layer, growing on the planarization layer.

[0030] In this application, by forming a pattern structure on the surface of a nitride single crystal substrate, then covering a nitride layer on the pattern structure, and making the nitride layer continue the morphology of the pattern structure, on the one hand, the pattern structure can be used to filter the dislocations of the nitride single crystal, and on the other hand, the pattern structure and the nitride layer can cooperate to form a light reflection interface with a larger area and better continuity, more efficiently reflect the light emitted by the light-emitting epitaxial layer, significantly improve the light extraction efficiency of the device, and at the same time, the nitride layer can be used to block and suppress the dislocations of the nitride single crystal substrate, further improve the quality of the epitaxial crystal, so that the finally obtained device is also further improved in terms of performance such as reverse leakage current and lifespan.

[0031] In this application, the pattern structure can be formed by physically and / or chemically processing the surface of the nitride single crystal substrate. It can be closely arranged or sparsely distributed on the surface of the nitride single crystal substrate and exhibit a certain repetition period. And the shape, size, spacing, etc. of the pattern structure can be adjusted according to actual application requirements.

[0032] In one embodiment, the pattern structure includes pits in the shape of a funnel or an inverted truncated cone formed on the surface of the nitride single crystal substrate, such as V-shaped pits. Compared with pattern structures of other shapes, on the one hand, the side walls of the V-shaped pits covering the nitride layer can increase total reflection, thereby further increasing the light reflection efficiency. On the other hand, the inside of the V-shaped pits can induce lateral growth, improve the efficiency of filtering dislocations, be more conducive to improving the quality of homoepitaxial crystals, and at the same time, it is easier to fabricate by means of dry etching, wet etching, etc., and the process is more controllable.

[0033] Furthermore, the opening angle of the pit can be 15° - 75°, the depth can be 100 nm - 10 μm, and the opening diameter can be 10 nm - 1 μm. If the size of the pit is too small, it will be difficult to achieve the above-mentioned effects of increasing the light reflection efficiency and improving the dislocation filtering efficiency. If the size of the pit is too large, it may lead to uneven subsequent epitaxial growth and a decline in crystal quality.

[0034] Furthermore, the spacing between two adjacent pits can be 1 μm - 10 μm. If the distance between adjacent pits is too large, its positive effects on the light reflection efficiency, dislocation filtering efficiency, etc. will be significantly inhibited. If the distance between adjacent pits is too small, that is, the pits are arranged too densely, it will have an adverse impact on the quality of both the nitride single crystal substrate itself and the epitaxial structure.

[0035] In one embodiment, the nitride layer is an Al-containing nitride layer, and the change trend of at least one of the opening angle, opening diameter, and depth of the pits is negatively correlated with the change trend of the Al content in the nitride layer. That is, the higher the Al component of the nitride layer, the shallower the depth of the pits, the smaller the opening, and the smaller the spacing should be, which is beneficial to Al migration and is beneficial to the growth of the nitride layer and the filling layer.

[0036] In one embodiment, the nitride layer has a first region and a second region, where the first region corresponds to the pattern structure, and the second region corresponds to the region between adjacent pattern structures; the thickness of the second region is less than the average thickness of each region of the nitride layer, and / or a roughened structure is formed on the surface of the second region.

[0037] More preferably, the thickness of the second region is 100 nm - 150 nm.

[0038] More preferably, the Ra value of the surface roughness of the second region is greater than 0.1 μm, preferably 0.1 μm - 0.9 μm.

[0039] Among them, by thinning a partial region of the nitride layer at the position of the adjacent pit interval (i.e., the second region), the dislocation density in the subsequently grown epitaxial structure can be further reduced, and the overall thinning of the nitride layer is also avoided; however, it should be noted that the nitride layer at these positions should not be too thin to avoid causing holes during subsequent temperature rise for epitaxial growth. The thickness of the second region is set to be less than the average thickness of each region of the nitride layer, preferably 100 nm - 150 nm.

[0040] Among them, by roughening the surface of a partial region of the nitride layer at the position of the adjacent pit interval, the light reflected by the aforementioned light reflection interface can be more effectively prevented from returning to the active region along the original path, and the absorption of light by the nitride single crystal substrate can be reduced, thereby more effectively improving the light extraction efficiency of the device.

[0041] When the thinning and surface roughening methods are simultaneously used to process the second region, the advantages of these two methods can be fully utilized, especially for micro-LEDs, mini-LEDs and other micro-sized LEDs, which have a more significant effect on improving the light efficiency.

[0042] In one embodiment, the filling layer includes a nucleation layer, a 3D layer, and a merging layer that are sequentially grown on the nitride layer.

[0043] Among them, the thickness of the nucleation layer can be 0 - 50 nm. Depending on the material and size of the nitride layer, the nucleation layer can also be selected not to be provided.

[0044] Among them, the thickness of the 3D layer can be 300 nm - 800 nm.

[0045] Among them, the thickness of the merging layer can be 500 nm - 1500 nm.

[0046] In one embodiment, the material of the nitride layer includes InAlN, AlN, etc., and is not limited thereto. Preferably, the nitride layer is lattice-matched with the nitride single crystal substrate. Compared with other materials such as alumina and silica, the materials of InAlN, AlN, etc. are the same or similar to those of the nitride single crystal substrate, and are very stable at the epitaxial growth temperature, can always maintain a firm bond with the nitride single crystal substrate, and can more effectively ensure the uniformity and crystal quality of epitaxial growth.

[0047] In one embodiment, the thickness of the nitride layer is 50 nm - 500 nm. If it is too thin, it is easy to decompose and form holes during the heating process, which is not conducive to the continuity of the interface; but if it is too thick, it will cause an increase in stress and to a certain extent affect the crystal quality of the subsequent grown epitaxial structure. Of course, considering the very high crystal quality of the nitride single crystal substrate, this influence is relatively small. More preferably, the thickness of the nitride layer is 100 nm - 200 nm.

[0048] In the present application, the group III nitride single crystal substrate can be a GaN single crystal substrate, an AlN single crystal substrate, etc., and is not limited thereto. Further, the group III nitride single crystal substrate can be n-type doped, p-type doped or undoped.

[0049] In one embodiment, the light-emitting epitaxial layer includes a first semiconductor layer of a first conductivity type, a quantum well active region, and a second semiconductor layer of a second conductivity type, which are sequentially grown on the planarizing layer.

[0050] Among them, the first conductivity type can be n-type, and correspondingly, the second conductivity type is p-type, and vice versa.

[0051] Among them, the materials of the first semiconductor layer, the active region, and the second semiconductor layer can be selected from group III-V compounds, such as group III nitrides such as GaN, InGaN, and AIInGaN, and are not limited thereto.

[0052] For example, the first semiconductor layer can be an N-type layer, which can further include a highly doped N-type GaN layer, an N-Al electron spreading layer, and a low-doped N-type GaN layer, etc.

[0053] For example, the quantum well active region may include a multi - quantum well (MQWs) light - emitting layer, etc., and is not limited thereto. For example, the quantum well active region may contain InGaN, etc. More specifically, the quantum well active region may be a multi - quantum well light - emitting layer composed of a plurality of alternately grown InGaN quantum wells and a plurality of GaN quantum barriers. Further, the quantum well active region may specifically include an SRL stress - releasing layer, a shadow quantum well structure, a light - emitting quantum well structure, etc.

[0054] For example, the second semiconductor layer may be a P - type layer, which may further include a low - temperature P - type layer, an EBL electron - blocking layer, a high - temperature P - type layer, etc.

[0055] A method for fabricating the light - emitting diode structure based on a patterned nitride single - crystal substrate provided by some embodiments of the present application includes:

[0056] Processing a plurality of regular pattern structures on the surface of the nitride single - crystal substrate, where the pattern structures protrude or recess with respect to the surface of the nitride single - crystal substrate;

[0057] Forming a nitride layer on the plurality of pattern structures, and making the nitride layer continuously conformally cover the plurality of pattern structures, and making the nitride layer cooperate with the plurality of pattern structures to form a reflection structure, where the reflection structure can at least reflect the light emitted by the light - emitting epitaxial layer;

[0058] Growing a planarizing layer with a flat surface on the nitride layer; and

[0059] Growing a light - emitting epitaxial layer on the planarizing layer.

[0060] In the present application, the morphology, size, arrangement manner, and spacing of the pattern structures, etc. may be as described above, and will not be elaborated here.

[0061] In one embodiment, the preparation method specifically includes: etching the surface of the nitride single - crystal substrate by dry etching and / or wet etching to form the pattern structures.

[0062] Among them, the surface of the nitride single - crystal substrate may refer to the nitrogen surface or the gallium surface of the nitride single - crystal substrate. For the nitride single - crystal substrate, its nitrogen surface has very active chemical properties. Under the same conditions, it is more susceptible to corrosion and etching compared to the gallium surface. Therefore, simple and easy - to - operate wet etching can be used, and chemical solutions can be used for immersion corrosion to form the aforementioned pattern structures. Applicable chemical solutions may include potassium hydroxide solution, phosphoric acid solution, NH4OH / H2O2 mixed solution, etc., and are not limited thereto. The aforementioned wet etching can be carried out at room temperature or heating conditions. Of course, dry etching, etc. can also be performed on the gallium surface of the nitride single - crystal substrate to form the aforementioned pattern structures.

[0063] In one embodiment, the preparation method includes: forming the nitride layer using an Al-containing nitride, and correspondingly reducing or increasing at least one of the opening angle, opening diameter, and depth of the pit as the Al content in the nitride layer increases or decreases.

[0064] In one embodiment, the preparation method further includes:

[0065] defining a first region and a second region in the nitride layer, where the first region corresponds to the pattern structure, and the second region corresponds to the region between adjacent pattern structures; and

[0066] thinning the second region of the nitride layer until the thickness of the second region is less than the average thickness of each region of the nitride layer, and / or roughening the surface of the second region of the nitride layer until the Ra value of the surface roughness of the second region is greater than 0.1 μm, preferably 0.1 μm - 0.9 μm.

[0067] Among them, the thinning process can be achieved by CMP (chemical mechanical polishing) or other physical and chemical methods, and the thinning amplitude can be as described above.

[0068] Among them, the roughening process can be achieved by the aforementioned dry etching, wet etching, etc., and the finally formed roughened structure can be as described above.

[0069] In one embodiment, the preparation method specifically includes: sequentially growing a nucleation layer, a 3D layer, and a merging layer on the nitride layer to form the filling layer. Among them, whether to grow a nucleation layer can be determined according to the material, thickness, etc. of the nitride layer. The 3D layer is a three-dimensional longitudinal growth mode, and the height depends on the height of the pattern structure. The merging layer is a two-dimensional lateral growth mode, and finally fills the pattern structure to form a flat semiconductor material layer.

[0070] In one embodiment, the preparation method specifically includes: sequentially growing a first semiconductor layer of a first conductivity type, a quantum well active region, and a second semiconductor layer of a second conductivity type on the filling layer to form the light-emitting epitaxial layer.

[0071] Among them, the material and thickness of the nitride layer, the material of the nitride single crystal substrate, the structure and material of the light-emitting epitaxial layer, etc. are all as described above.

[0072] In the present application, each semiconductor material layer in the filling layer and the light-emitting epitaxial layer can be grown and formed by means of HVPE (hydride vapor phase epitaxy), MOCVD (metalorganic chemical vapor deposition), PECVD (plasma enhanced chemical vapor deposition), etc., and is not limited thereto.

[0073] In the present application, the nitride layer can also be formed by physical and / or chemical vapor deposition methods, such as sputtering, MOCVD, ALD, PEDCVD, etc., and is not limited thereto.

[0074] In one embodiment, the growth of the nitride layer, the planarization layer, and the light-emitting epitaxial layer can be continuously completed within the same epitaxial growth device, so as to further reduce the influence of the external environment on the device quality and obtain a light-emitting diode structure with more excellent performance.

[0075] Please refer to Figure 1 - Figure 2 As shown, in the first embodiment of the present application, a light-emitting diode structure based on a patterned nitride single crystal substrate includes:

[0076] A nitride single crystal substrate 1, on the surface of which a plurality of regular pattern structures are formed. The pattern structures can be V-shaped pits 11, and a plurality of V-shaped pits are arranged in an array;

[0077] A nitride layer 2, which continuously conformally covers the plurality of pattern structures and cooperates with the plurality of pattern structures to form a reflection structure. The reflection structure can reflect the light emitted by the light-emitting epitaxial layer, and the nitride layer is lattice-matched with the nitride single crystal substrate;

[0078] A planarization layer 3, which continuously covers the nitride layer and has a flat surface. The planarization layer 3 includes a nucleation layer 31, a 3D layer 32, and a merging layer 33 formed in sequence; and

[0079] A light-emitting epitaxial layer 4, which grows on the planarization layer and includes an N-type region 41 (i.e., the aforementioned first semiconductor layer), a quantum well active region 42, and a P-type region 43 (i.e., the aforementioned second semiconductor layer) formed in sequence. The N-type region 41, the quantum well active region 42, and the P-type region 43 may each further include other more structural layers known to those skilled in the art, which are not shown in the figure here.

[0080] Please continue to refer to Figure 3 , a method for preparing the light-emitting diode structure includes:

[0081] First, the surface of the GaN single crystal substrate 1 is etched to form a plurality of regular pattern structures, and a patterned GaN single crystal substrate is obtained. The morphology, size, spacing, etc. of the pattern structures can be as described above. For example, the V-shaped pits can have an opening angle α of 15° - 75°, a depth d of 100 nm - 10 μm, an opening diameter r of 10 nm - 1 μm, and the spacing L between adjacent V-shaped pits is 1 μm - 10 μm. The etching method used can be wet etching or dry etching.

[0082] Next, place this graphitized GaN single-crystal substrate into a sputtering system or other physical / chemical vapor deposition system to deposit the nitride layer 2. The material of the nitride layer is preferably InAlN, AlN, etc., and the thickness can be 50 nm - 500 nm, preferably 100 nm - 200 nm;

[0083] After that, perform the MOCVD epitaxial process. A nucleation layer, a 3D layer, and a merging layer are sequentially grown on the surface of this graphitized GaN single-crystal substrate to form a planarizing layer 3. Then, an N-type region, a quantum well active region, and a P-type region are sequentially grown on the planarizing layer to form a light-emitting epitaxial layer 4, and finally, a light-emitting diode structure based on GaN homoepitaxy with high luminous efficiency is obtained.

[0084] The method provided in this exemplary embodiment is also applicable to the preparation of light-emitting diode structures based on AlN single-crystal substrates, etc.

[0085] In the preparation method of the present application, by first etching a pattern structure on the nitride single-crystal substrate, the dislocations of the nitride single-crystal substrate can be filtered. Then, a nitride layer is deposited and made to continue the pattern structure. This nitride layer can cooperate with the pattern structure to form a more continuous and larger-area light reflection interface, which plays a reflective role, and it has better lattice matching with the nitride single-crystal substrate and can also block and suppress the dislocations of the nitride single-crystal substrate.

[0086] In the second embodiment of the present application, a light-emitting diode structure based on a graphitized nitride single-crystal substrate is as shown Figure 4 - Figure 5 as follows, which is basically the same as the light-emitting diode structure shown Figure 1 except that a roughened structure 21 is formed on the surface of the region of the nitride layer 2 corresponding to the adjacent pit interval positions to further improve the light extraction efficiency, and the principle is as described above. Moreover, this roughened structure 21 is more conducive to the growth of the nucleation layer 31 in the planarizing layer 3.

[0087] In some alternative solutions, the region of the nitride layer 2 corresponding to the adjacent pit interval positions can also be thinned, or both thinned and formed with a roughened structure, and the advantages are as described above.

[0088] Correspondingly, a method for preparing this light-emitting diode structure can also be referred to Figure 3 as shown, but after forming the nitride layer and before growing the planarizing layer, it is necessary to first perform a thinning process and / or a surface roughening process on the region of the nitride layer corresponding to the adjacent pit interval positions.

[0089] Some embodiments of the present application also provide a light-emitting diode, which includes:

[0090] The above-mentioned light-emitting diode structure based on a graphitized nitride single-crystal substrate; and

[0091] An electrode cooperating with the light-emitting diode structure.

[0092] In one embodiment, the electrode may include a first electrode, a second electrode, etc. that cooperate with the light-emitting diode structure. For example, the first electrode is an N electrode and the second electrode is a P electrode, and vice versa. The setting manner of the electrode is well-known in the art and will not be elaborated here.

[0093] Hereinafter, the technical solution of the present application will be described in more detail in conjunction with the accompanying drawings and several embodiments. It should be understood, however, that the following embodiments are only for explaining and illustrating the technical solution and do not limit the scope of the present application. Also, unless otherwise specified, various raw materials, reaction equipment, detection equipment, and methods used in the following embodiments are all known in the art.

[0094] Embodiment 1 This embodiment provides a light-emitting diode structure based on a GaN single-crystal substrate, and its structure can be referred to Figure 1 , including a GaN single-crystal substrate and an AlN layer, a filling layer, and a light-emitting epitaxial layer sequentially grown on the substrate. Among them, a plurality of uniformly distributed V-shaped pits are formed on the surface of the GaN single-crystal substrate. The filling layer includes a nucleation layer, a 3D layer, and a merging layer sequentially grown. The light-emitting epitaxial layer includes a highly doped N-type GaN layer, an N-Al electron spreading layer, a low-doped N-type GaN layer, an SRL stress release layer, a shadow quantum well structure, a light-emitting quantum well structure, a low-temperature P-type layer, an EBL electron blocking layer, and a high-temperature P-type layer sequentially grown.

[0095] A method for preparing the light-emitting diode structure includes the following steps:

[0096] S1. Place the GaN single-crystal substrate into an inductively coupled plasma (ICP) etching device, etch its surface to form uniform and regular V-shaped pits. The opening angle of the V-shaped pits is about 60°, the depth is about 0.5 μm, the opening diameter is about 0.1 μm, and the spacing between adjacent V-shaped pits is about 0.5 μm to obtain a patterned substrate.

[0097] S2. Place the patterned substrate processed in step S1 into a physical vapor deposition (PVD) device, and deposit AlN with a thickness of about 150 nm at 500 °C, which uniformly covers the surface of the patterned substrate.

[0098] S3, put the patterned substrate with AlN layer on the surface after the treatment in step S2 into the metal organic chemical vapor deposition (MOCVD) system, heat it to about 1020℃, pressure is about 500torrr, anneal for about 5 minutes, then introduce TMGa source, under the condition of V / III=800, carry out three-dimensional vertical growth of GaN, control the thickness to about 1.2μm, then heat it to about 1080℃ again, reduce the pressure to about 200torr, carry out two-dimensional lateral growth of GaN, control the thickness to about 1μm, ensure the surface is completely merged and the GaN material layer is flat. Then reduce the temperature to about 1050℃, grow the N-type region, including Si doped 1E19cm with a thickness of about 2μm -3 N-type GaN, Si doped with 2E18cm thick about 100nm -3 n-type AlGaN and Si doped 1E17cm thick with a thickness of about 200nm -3 Then the temperature is lowered to 880℃ to grow the SRL stress release layer, which is an InGaN / GaN cycle with a total thickness of about 150nm; the temperature is further lowered to about 805℃ to grow the shadow quantum well, which has 6 pairs of InGaN / GaN structures and a total thickness of about 72nm; then the temperature is lowered to about 780℃ to grow the light-emitting quantum well, which has 10 pairs of InGaN / GaN structures and a total thickness of about 150nm; at this temperature, the growth of the P-type region begins, starting with low-temperature P-type GaN with a Mg doping concentration of 2E20cm -3 The thickness is about 10nm, and the temperature is raised to about 980℃ to grow the EBL electron blocking layer, which is a P-type AlGaN layer with a Mg doping concentration of 5E19cm -3 , thickness is about 20nm, and finally high temperature P-type GaN is grown, with Mg doping concentration of 2E20cm -3 , with a thickness of about 50 nm. The light-emitting diode structure finally obtained can be named sample B.

[0099] Comparative Example 1 The light-emitting diode structure based on a GaN single crystal substrate provided in this comparative example is similar to that of Example 1, except that the surface of the GaN single crystal substrate is flat and has not been patterned.

[0100] A method for preparing the light-emitting diode structure is substantially the same as that of Example 1, except that step S1 is omitted, and in step S2, an AlN layer is directly deposited on the surface of a GaN single crystal substrate that has not been patterned. The light-emitting diode structure finally obtained can be named sample A. The AlN layer and epitaxial structure of samples A and B are grown in the same furnace.

[0101] Photoluminescence (PL) tests were conducted on samples A and B, and the results are shown in Table 1 below. For sample B among them, since its surface has been patterned and a nitride layer has been added, the exit angle of the emitted light reflected onto the substrate surface has been changed, significantly increasing the light extraction effect. The exit angle reflected onto the substrate has been changed, significantly increasing the light extraction effect. The actually obtained photoluminescence intensity is about 60% higher than that of sample A.

[0102] Comparative Example 2 A light-emitting diode structure based on a GaN single-crystal substrate and its preparation method provided in this comparative example are basically the same as those of sample B, except that: the AlN layer is omitted. The light-emitting diode structure of this comparative example can be named sample C.

[0103] Comparative Example 3 A light-emitting diode structure based on a GaN single-crystal substrate and its preparation method provided in this comparative example are basically the same as those of sample B, except that: the thickness of the AlN layer is adjusted to about 20 nm. The light-emitting diode structure of this comparative example can be named sample D.

[0104] Comparative Example 4 A light-emitting diode structure based on a GaN single-crystal substrate and its preparation method provided in this comparative example are basically the same as those of sample B, except that: the thickness of the AlN layer is adjusted to about 600 nm. The light-emitting diode structure of this comparative example can be named sample E.

[0105] Comparative Example 5 A light-emitting diode structure based on a GaN single-crystal substrate and its preparation method provided in this comparative example are basically the same as those of sample B, except that: the opening angle of the V-shaped pit is adjusted to about 85°, the opening diameter is adjusted to about 1.5 μm, the depth is adjusted to about 1.2 μm, and the spacing between adjacent V-shaped pits is adjusted to about 2 μm. The light-emitting diode structure of this comparative example can be named sample F.

[0106] Comparative Example 6 A light-emitting diode structure based on a GaN single-crystal substrate and its preparation method provided in this comparative example are basically the same as those of sample B, except that: the opening angle of the V-shaped pit is adjusted to about 60°, the opening diameter is adjusted to about 50 nm, the depth is adjusted to about 30 nm, and the spacing between adjacent V-shaped pits is adjusted to about 10 nm. The light-emitting diode structure of this comparative example can be named sample G.

[0107] Comparative Example 7 A light-emitting diode structure based on a GaN single-crystal substrate and its preparation method provided in this comparative example are basically the same as those of sample B, except that: the uniformly arranged multiple V-shaped pits are replaced with uniformly arranged multiple yurt-shaped protrusions, the bottom width of each protrusion is about 2.7 μm, the height is about 1.6 μm, and the spacing between adjacent protrusions is about 0.3 μm. The light-emitting diode structure of this comparative example can be named sample H.

[0108] Example 2 A light-emitting diode structure based on a GaN single-crystal substrate and its preparation method provided in this example are basically the same as those of Sample B, except that: the region of the AlN layer corresponding to the position of the adjacent pit intervals is thinned, with a thickness of about 100 nm. This thinning process is achieved by chemical mechanical polishing. After completing this thinning process, the filling layer and the light-emitting epitaxial layer are grown in sequence. The light-emitting diode structure of this example can be named Sample I.

[0109] Example 3 A light-emitting diode structure based on a GaN single-crystal substrate and its preparation method provided in this example are basically the same as those of Sample B, except that: the region of the AlN layer corresponding to the position of the adjacent pit intervals is surface roughened. This surface roughening process is specifically as follows: after forming the AlN layer, the surface of the region of the AlN layer corresponding to the position of the adjacent pit intervals is etched with a NaOH solution with a concentration of about 2 mol / L for about 5 minutes, then washed and dried, and then the filling layer and the light-emitting epitaxial layer are grown in sequence. The light-emitting diode structure of this example can be named Sample J.

[0110] Example 4 A light-emitting diode structure based on a GaN single-crystal substrate and its preparation method provided in this example are basically the same as those of Sample K, except that: the region of the AlN layer corresponding to the position of the adjacent pit intervals is first thinned to a thickness of about 100 nm and then surface roughened. After completing this surface roughening process, the filling layer and the light-emitting epitaxial layer are grown in sequence. The light-emitting diode structure of this example can be named Sample K.

[0111] The performance of Samples A - L was tested respectively, and the test results are shown in Table 1.

[0112] Table 1 Performance test results of Samples A - L

[0113]

[0114] Example 5 A light-emitting diode structure based on a GaN single-crystal substrate and its preparation method provided in this example are basically the same as those of Example 1, but the nitride layer therein is an AlN layer with a thickness of about 200 nm.

[0115] Example 6 A light-emitting diode structure based on a GaN single-crystal substrate and its preparation method provided in this example are basically the same as those of Example 1, but the nitride layer therein is an AlN layer with a thickness of about 50 nm.

[0116] Example 7 A light-emitting diode structure based on a GaN single-crystal substrate and its preparation method provided in this example are basically the same as those of Example 1, but the nitride layer therein is an InAlN layer with a thickness of about 500 nm.

[0117] The performance of the device in Example 5, such as the light extraction efficiency and light extraction uniformity, is close to that of Sample B. The devices in Examples 6 - 7 also have relatively high light extraction efficiency and light extraction uniformity, but are inferior to the devices in Examples 1 - 5 in these performance aspects.

[0118] Finally, it should be noted that the above are only the preferred embodiments of the present application and are not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A light-emitting diode structure based on a patterned nitride single crystal substrate, characterized in that, Comprising: A nitride single crystal substrate, on the surface of which a plurality of regular pattern structures are formed. The pattern structures include pits in a funnel shape or an inverted truncated pyramid shape formed on the surface of the nitride single crystal substrate. The opening angle of the pits is 15° - 75°, the depth is 100 nm - 10 μm, the opening diameter is 10 nm - 1 μm, and the distance between two adjacent pits is 1 μm - 10 μm; A nitride layer, continuously and conformally covering the plurality of pattern structures, and cooperating with the plurality of pattern structures to form a reflection structure. The reflection structure can at least reflect the light emitted by the light-emitting epitaxial layer. The nitride layer has a first region and a second region. The first region corresponds to the pattern structure, and the second region corresponds to the region between adjacent pattern structures. A roughened structure is formed on the surface of the second region, so that the Ra value of the surface roughness of the second region is greater than 0.1 μm; A planarizing layer, continuously covering the nitride layer, and the surface of the planarizing layer is flat; And a light-emitting epitaxial layer, grown on the planarizing layer; Wherein, the nitride layer is lattice-matched with the nitride single crystal substrate.

2. The light-emitting diode structure based on a patterned nitride single crystal substrate according to claim 1, wherein: The thickness of the nitride layer is 50 - 500 nm.

3. The light-emitting diode structure based on the patterned nitride single crystal substrate according to claim 2, wherein: The nitride layer is an Al-containing nitride layer with a thickness of 100 nm - 200 nm.

4. The light-emitting diode structure based on a patterned nitride single-crystal substrate according to claim 1, wherein: The nitride layer is an Al-containing nitride layer, and at least one of the opening angle, opening diameter, and depth of the pits decreases as the Al content in the nitride layer increases, and at least one of the opening angle, opening diameter, and depth of the pits increases as the Al content in the nitride layer decreases.

5. The light-emitting diode structure based on a patterned nitride single-crystal substrate according to claim 1, wherein: The thickness of the second region is less than or equal to the average thickness of each region of the nitride layer.

6. The light-emitting diode structure based on the patterned nitride single-crystal substrate according to claim 5, wherein: The thickness of the second region is 100 nm - 150 nm.

7. The light-emitting diode structure based on a patterned nitride single-crystal substrate according to claim 5, wherein: The Ra value of the surface roughness of the second region is 0.1 μm - 0.9 μm.

8. The light emitting diode structure based on a patterned nitride single crystal substrate according to claim 1, characterized in that: The planarizing layer includes a nucleation layer, a 3D layer, and a merging layer that are sequentially grown on the nitride layer. The thickness of the nucleation layer is 0 - 50 nm, the thickness of the 3D layer is 300 nm - 800 nm, and the thickness of the merging layer is 500 nm - 1500 nm.

9. The light-emitting diode structure based on a patterned nitride single crystal substrate according to claim 1, characterized in that: The light-emitting epitaxial layer includes a first semiconductor layer of a first conductivity type, a quantum well active region, and a second semiconductor layer of a second conductivity type that are sequentially grown on the planarizing layer.

10. The light-emitting diode structure based on a patterned nitride single crystal substrate according to claim 1, wherein: The material of the nitride layer includes InAlN or AlN.

11. The light-emitting diode structure based on a patterned nitride single-crystal substrate according to claim 1, wherein: The nitride single crystal substrate includes a GaN single crystal substrate or an AlN single crystal substrate.

12. A method for preparing a light-emitting diode structure based on a patterned nitride single-crystal substrate, characterized in that, Comprising: Processing a plurality of regular pattern structures on the surface of a nitride single crystal substrate. The pattern structures include pits in a funnel shape or an inverted truncated pyramid shape formed on the surface of the nitride single crystal substrate. The opening angle of the pits is 15° - 75°, the depth is 100 nm - 10 μm, the opening diameter is 10 nm - 1 μm, and the distance between two adjacent pits is 1 μm - 10 μm; A nitride layer is formed on a plurality of the pattern structures, and the nitride layer continuously conformally covers the plurality of pattern structures. The nitride layer also cooperates with the plurality of pattern structures to form a reflective structure, which can at least reflect the light emitted by the light-emitting epitaxial layer. The nitride layer is lattice-matched with the nitride single-crystal substrate; A first region and a second region are defined in the nitride layer, wherein the first region corresponds to the pattern structure, and the second region corresponds to the region between adjacent pattern structures. The surface of the second region of the nitride layer is roughened until the Ra value of the surface of the second region is greater than 0.1 μm; A planarizing layer with a flat surface is grown on the nitride layer; And a light-emitting epitaxial layer is grown on the planarizing layer.

13. The method for preparing a light-emitting diode structure based on a patterned nitride single-crystal substrate according to claim 12, characterized in that: The nitride layer is formed of an Al-containing nitride, and at least one of the opening angle, opening diameter, and depth of the pit is correspondingly reduced as the Al content in the nitride layer increases, and at least one of the opening angle, opening diameter, and depth of the pit is correspondingly increased as the Al content in the nitride layer decreases.

14. The method for preparing a light-emitting diode structure based on a patterned nitride single-crystal substrate according to claim 12, characterized in that: The material of the nitride layer includes InAlN or AlN.

15. The method for preparing a light-emitting diode structure based on a patterned nitride single-crystal substrate according to claim 12, wherein: The nitride single-crystal substrate includes a GaN single-crystal substrate or an AlN single-crystal substrate.

16. The manufacturing method of a light-emitting diode structure based on a patterned nitride single crystal substrate according to claim 12, characterized in that, Specifically, it includes: The surface of the nitride single-crystal substrate is etched by dry etching and / or wet etching to form the pattern structure.

17. The manufacturing method of a light-emitting diode structure based on a patterned nitride single crystal substrate according to claim 12, wherein, It also includes: The second region of the nitride layer is thinned until the thickness of the second region is less than the average thickness of each region of the nitride layer.

18. The manufacturing method of a light-emitting diode structure based on a patterned nitride single crystal substrate according to claim 12, wherein: The thickness of the nitride layer is 50 - 500 nm.

19. The manufacturing method of the light-emitting diode structure based on the patterned nitride single crystal substrate according to claim 18, wherein: The nitride layer is an Al-containing nitride layer with a thickness of 100 nm - 200 nm.

20. The method for preparing a light-emitting diode structure based on a patterned nitride single crystal substrate according to claim 12, wherein Specifically, it includes: A nucleation layer, a 3D layer, and a merging layer are sequentially grown on the nitride layer to form the planarizing layer.

21. The preparation method of the light-emitting diode structure based on the patterned nitride single crystal substrate according to claim 12, characterized in that, Specifically, it includes: A first semiconductor layer of a first conductivity type, a quantum well active region, and a second semiconductor layer of a second conductivity type are sequentially grown on the planarizing layer to form the light-emitting epitaxial layer.

Images