Method for preparing ultraviolet light-emitting diode epitaxial wafer with improved luminous efficiency

Abstract

The present invention provides a method for preparing an ultraviolet light-emitting diode epitaxial wafer with improved luminous efficiency, and belongs to the technical field of light-emitting diodes. At least one well barrier unit is grown on an n-type AlGaN layer to obtain a light-emitting layer, and the well barrier unit includes an AlGaN barrier layer and AlGaN quantum dots stacked on the AlGaN barrier layer and spaced from each other. The structure of the AlGaN quantum dots has a three-dimensional quantum confinement effect, which improves the luminous efficiency. First, a layer of AlGaN barrier layer is grown on the n-type AlGaN layer or the well barrier unit; and a 1-5 nm AlN material layer is deposited on the AlGaN barrier layer. The AlN material layer is annealed so that the surface of the AlN material layer has a plurality of protruding island structures to release stress. Finally, a gallium source and ammonia are introduced into the reaction chamber to react with the plurality of island structures to generate a plurality of AlGaN quantum dots with better quality and faster formation, which can promote the luminous efficiency while improving the forming efficiency of the light-emitting layer.

Description

Technical field

[0001] The present disclosure relates to the technical field of light-emitting diodes, and in particular to a method for preparing an ultraviolet light-emitting diode epitaxial wafer that improves luminous efficiency. Background technology

[0002] With the development of light-emitting diode applications, the market demand for ultraviolet light-emitting diodes is growing. Ultraviolet light-emitting diodes with a luminous wavelength covering 210 to 400 nm have advantages that traditional ultraviolet light sources cannot match. UV light-emitting diodes are commonly used in lighting, biomedical treatment, anti-counterfeiting identification, air and water purification, biochemical testing, high-density information storage, etc.

[0003] In recent years, AlGaN-based high-brightness UV light-emitting diodes have been developed. The basic structure of an epitaxial wafer of an AlGaN-based UV light-emitting diode is usually a substrate and a buffer layer, an n-type AlGaN layer, a light-emitting layer and a p-type AlGaN layer deposited on the substrate in sequence. Carriers enter the light-emitting layer from other layers and recombine to emit light.

[0004] The luminous power of UV light-emitting diodes is mainly determined by external quantum efficiency, and the external quantum efficiency of UV light-emitting diodes can be expressed as the product of injection efficiency, internal quantum efficiency and light extraction efficiency. Therefore, the internal quantum efficiency of the active area directly determines the efficiency of the device. and output power. However, the internal quantum efficiency of AlGaN-based UV light-emitting diodes is mainly determined by the number and recombination efficiency of carriers in the light-emitting layer. There are many defects inside the light-emitting layer of AlGaN-based UV light-emitting diode epitaxial wafers and there is a certain polarization effect. Under such circumstances, defects and polarization effects will lead to a reduction in the number of carriers and recombination efficiency, affecting the luminous efficiency of the final ultraviolet light-emitting diode epitaxial wafer. Contents of the invention

[0005] Embodiments of the present disclosure provide a method for preparing an ultraviolet light-emitting diode epitaxial wafer that improves luminous efficiency, which can improve the recombination efficiency of carriers in the luminescent layer to improve the luminous efficiency of the ultimately obtained ultraviolet light-emitting diode epitaxial wafer. The technical solutions are as follows:

[0006] Embodiments of the present disclosure provide a method for preparing an ultraviolet light-emitting diode epitaxial wafer that improves luminous efficiency. The method for preparing an ultraviolet light-emitting diode epitaxial wafer that improves luminous efficiency includes:

[0007] provide a substrate;

[0008] growing a buffer layer on the substrate;

[0009] Grow an n-type AlGaN layer on the buffer layer;

[0010] Growing at least one well barrier unit on the n-type AlGaN layer to obtain a light-emitting layer, the well barrier unit including an AlGaN barrier layer and AlGaN quantum dots stacked on the AlGaN barrier layer and spaced apart from each other;

[0011] Grow a p-type AlGaN layer on the light-emitting layer;

[0012] Growing each of the well barrier cells includes:

[0013] grow an AlGaN barrier layer on the n-type AlGaN layer or the well barrier unit;

[0014] Deposit an AlN material layer of 1 to 5 nm on the AlGaN barrier layer;

[0015] Annealing the AlN material layer so that the surface of the AlN material layer has a plurality of raised island structures;

[0016] A gallium source and ammonia gas are introduced into the reaction chamber to react with a plurality of the island structures to generate a plurality of the AlGaN quantum dots.

[0017] Optionally, the deposition rate of the AlN material layer is 0.1 nm / s to 1 nm / s.

[0018] Optionally, the annealing temperature of the AlN material layer is 1000-1200°C, and the annealing time of the AlN material layer is 800-1000 s.

[0019] Optionally, the V / III molar ratio of the gallium source and the ammonia gas introduced into the reaction chamber is 100 to 2000:1.

[0020] Optionally, the stacking density of the plurality of AlGaN quantum dots on the AlGaN barrier layer is 1 to 6×10 11 cm -2 .

[0021] Optionally, the diameter of each AlGaN quantum dot is 1 to 5 nm.

[0022] Optionally, the growth rate of the AlGaN barrier layer is 0.01˜0.2 nm / s.

[0023] Optionally, the thickness of the AlGaN barrier layer is 5 to 15 nm.

[0024] Optionally, the growth temperature of the AlGaN barrier layer is 1000-1200°C, and the growth pressure of the AlGaN barrier layer is 50-200 mbar.

[0025] Optionally, growing a buffer layer on the substrate includes:

[0026] An AlN sublayer, an AlN / AlGaN multi-period stress modulation sublayer and an undoped AlGaN sublayer are grown sequentially on the substrate to obtain the buffer layer.

[0027] The beneficial effects brought by the technical solutions provided by the embodiments of the present disclosure include:

[0028] When growing ultraviolet light-emitting diode epitaxial wafers, after growing the buffer layer and the n-type AlGaN layer, grow at least one well barrier unit on the n-type AlGaN layer to obtain a light-emitting layer. The well barrier unit includes an AlGaN barrier layer and a layer stacked on the AlGaN barrier layer. and spaced AlGaN quantum dots. In the well barrier unit that constitutes the light-emitting layer, on the one hand, the structure of AlGaN quantum dots has a three-dimensional quantum confinement effect, which can more effectively capture carriers and prevent carriers from being captured by non-radiative recombination centers, thus improving the effective recombination of carriers. , improve the luminous efficiency of the luminescent layer to improve the luminous efficiency of the obtained ultraviolet light-emitting diode. In the growth process of AlGaN quantum dots, an AlGaN barrier layer is first grown on the n-type AlGaN layer or well barrier unit; an AlN material layer of 1 to 5 nm is deposited on the AlGaN barrier layer; the AlGaN barrier layer can play a good role. The transition effect provides a good growth foundation for the AlN material layer, ensuring that the quality of the AlGaN quantum dots obtained from the reaction growth of the AlN material layer is good; and the thickness of the AlN material layer is reasonable, which can facilitate the subsequent formation of the island structure. And before the AlN material layer generates AlGaN quantum dots, the AlN material layer is annealed so that the surface of the AlN material layer has multiple raised island structures. On the one hand, it can release the AlN material layer and the AlGaN barrier layer accumulated during the growth process. stress, reducing defects caused by stress that exist inside the luminescent layer. On the other hand, it can also make the island-like structure more complete. The surface of the island-like structure is easier to react with reactive gases and organic metal sources, promoting the formation of AlGaN quantum dots. take shape. Finally, a gallium source and ammonia gas are introduced into the reaction chamber to react with multiple island structures to generate multiple AlGaN quantum dots with better quality and faster formation, which can promote luminous efficiency and improve the forming efficiency of the luminescent layer. Description of drawings

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the drawings needed to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present disclosure. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without exerting creative efforts.

[0030] Figure 1 It is a flow chart of a method for preparing an ultraviolet light-emitting diode epitaxial wafer that improves luminous efficiency provided by an embodiment of the present disclosure;

[0031] Figure 2 It is a schematic structural diagram of an ultraviolet light-emitting diode epitaxial wafer that improves luminous efficiency provided by an embodiment of the present disclosure;

[0032] Figure 3 It is a flow chart of another method for preparing an ultraviolet light-emitting diode epitaxial wafer that improves luminous efficiency provided by an embodiment of the present disclosure;

[0033] Figure 4 This is a schematic structural diagram of another ultraviolet light-emitting diode epitaxial wafer that improves luminous efficiency provided by an embodiment of the present disclosure. Detailed implementation

[0034] In order to make the purpose, technical solutions and advantages of the present disclosure clearer, the embodiments of the present disclosure will be described in further detail below in conjunction with the accompanying drawings.

[0035] Unless otherwise defined, technical or scientific terms used herein shall have their ordinary meaning understood by a person of ordinary skill in the art to which this disclosure belongs. "First", "second", "third" and similar words used in the specification and claims of this patent application do not indicate any order, quantity or importance, but are only used to distinguish different components. . Likewise, "a" or "one" and similar words do not indicate a quantitative limit, but rather indicate the presence of at least one. "Including" or "includes" and other similar words mean that the elements or things appearing before "includes" or "includes" cover the elements or things listed after "includes" or "includes" and their equivalents, and do not exclude others. Component or object. Words such as "connected" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Top", "bottom", "left", "right", "top", "bottom", etc. are only used to express relative position relationships. When the absolute position of the described object changes, the relative position relationship may also be Change accordingly.

[0036] Figure 1 It is a flow chart of a method for preparing an ultraviolet light-emitting diode epitaxial wafer that improves luminous efficiency provided by an embodiment of the present disclosure. Please refer to Figure 1 It can be seen that the embodiments of the present disclosure provide a method for preparing an ultraviolet light-emitting diode epitaxial wafer that improves luminous efficiency. The method of preparing an ultraviolet light-emitting diode epitaxial wafer that improves luminous efficiency includes:

[0037] S101: Provide a substrate.

[0038] S102: Grow a buffer layer on the substrate.

[0039] S103: Grow an n-type AlGaN layer on the buffer layer.

[0040] S104: Grow at least one well barrier unit on the n-type AlGaN layer to obtain a light-emitting layer. The well barrier unit includes an AlGaN barrier layer and AlGaN quantum dots stacked on the AlGaN barrier layer and spaced apart from each other. Growing each well barrier unit includes: growing an AlGaN barrier layer on the n-type AlGaN layer or well barrier unit; depositing an AlN material layer of 1 to 5 nm on the AlGaN barrier layer; annealing the AlN material layer to make the AlN material The surface of the layer has multiple convex island structures; a gallium source and ammonia gas are introduced into the reaction chamber to react with the multiple island structures to generate multiple AlGaN quantum dots.

[0041] S105: Grow a p-type AlGaN layer on the light-emitting layer.

[0042] When growing ultraviolet light-emitting diode epitaxial wafers, after growing the buffer layer and the n-type AlGaN layer, grow at least one well barrier unit on the n-type AlGaN layer to obtain a light-emitting layer. The well barrier unit includes an AlGaN barrier layer and a layer stacked on the AlGaN barrier layer. and spaced apart AlGaN quantum dots. In the well barrier unit that constitutes the light-emitting layer, on the one hand, the structure of AlGaN quantum dots has a three-dimensional quantum confinement effect, which can more effectively capture carriers and prevent carriers from being captured by non-radiative recombination centers, thus improving the effective recombination of carriers. , improve the luminous efficiency of the luminescent layer to improve the luminous efficiency of the obtained ultraviolet light-emitting diode. In the growth process of AlGaN quantum dots, an AlGaN barrier layer is first grown on the n-type AlGaN layer or well barrier unit; an AlN material layer of 1 to 5 nm is deposited on the AlGaN barrier layer; the AlGaN barrier layer can play a good role. The transition effect provides a good growth foundation for the AlN material layer, ensuring that the quality of the AlGaN quantum dots obtained from the reaction growth of the AlN material layer is good; and the thickness of the AlN material layer is reasonable, which can facilitate the subsequent formation of the island structure. And before the AlN material layer generates AlGaN quantum dots, the AlN material layer is annealed so that the surface of the AlN material layer has multiple raised island structures. On the one hand, it can release the AlN material layer and the AlGaN barrier layer accumulated during the growth process. stress, reducing defects caused by stress that exist inside the luminescent layer. On the other hand, it can also make the island-like structure more complete. The surface of the island-like structure is easier to react with reactive gases and organic metal sources, promoting the formation of AlGaN quantum dots. take shape. Finally, a gallium source and ammonia gas are introduced into the reaction chamber to react with multiple island structures to generate multiple AlGaN quantum dots with better quality and faster formation, which can promote luminous efficiency and improve the forming efficiency of the luminescent layer.

[0043] For example, the AlN material layer can be grown using physical vapor deposition equipment. The crystal quality of the obtained AlGaN quantum dots can be improved.

[0044] Optionally, the physical vapor deposition method is one of magnetron sputtering, radio frequency sputtering or electron beam evaporation. It can be ensured that the quality of the obtained AlN material layer is good.

[0045] Optionally, the deposition rate of the AlN material layer is 0.1nm / s˜1nm / s.

[0046] The deposition rate of the AlN material layer is within the above range. On the one hand, it can ensure that the quality of the obtained AlN material layer is better. On the other hand, it can also ensure the growth efficiency of the AlN material layer. The island-like structure on the surface of the obtained AlN material layer is also better. Easy to shape.

[0047] Optionally, the annealing temperature of the AlN material layer is 1000-1200°C, and the annealing time of the AlN material layer is 800-1000s.

[0048] The annealing temperature and annealing time of the AlN material layer are within the above range, which can ensure that the AlN material layer is fully annealed and effectively improve the crystal quality of the obtained AlN material layer.

[0049] Optionally, the V / III molar ratio of the gallium source and ammonia gas that is introduced into the reaction chamber to react with the AlN material layer is 100 to 2000:1.

[0050] The V / III molar ratio of the gallium source and ammonia gas introduced into the reaction chamber to react with the AlN material layer is within the above range, which can ensure that the amounts of the gallium source and ammonia gas introduced are relatively reasonable, ensuring that the gallium source and ammonia gas and the AlN layer are sufficient reaction between them, and reduce the possible presence of organic metal sources or ammonia residues in the reaction chamber, facilitating gas scrubbing and subsequent growth of other epitaxial materials with different properties.

[0051] It should be noted that the V / III molar ratio is the molar ratio of the atomic masses of the potassium element in the gallium source and the nitrogen element in the ammonia gas.

[0052] Optionally, the stacking density of multiple AlGaN quantum dots on the AlGaN barrier layer is 1 to 6×10 11 cm -2 .

[0053] The stacking density of the obtained AlGaN quantum dots on the AlGaN barrier layer is within the above range, which can ensure a reasonable density of AlGaN quantum dots and can effectively capture most of the carriers to ensure the luminous efficiency of the obtained luminescent layer.

[0054] Optionally, the diameter of each AlGaN quantum dot is 1 to 5 nm.

[0055] The quality of the formed AlGaN quantum dots is good, and each AlGaN quantum dot can also provide enough space for capturing carriers and emitting light, effectively improving the luminous efficiency of the final ultraviolet light-emitting diode.

[0056] For ease of understanding, provided here Figure 2 , Figure 2 It is a schematic structural diagram of an ultraviolet light-emitting diode epitaxial wafer that improves luminous efficiency provided by an embodiment of the present disclosure. Figure 2 Chinese epitaxial wafers are produced by Figure 1 The ultraviolet light-emitting diode epitaxial wafer is prepared by the preparation method shown in, refer to Figure 2 It can be seen that the ultraviolet light-emitting diode epitaxial wafer that improves the luminous efficiency can include a substrate 1 and a buffer layer 2, an n-type AlGaN layer 3, a light-emitting layer 4 and a p-type AlGaN layer 5 sequentially stacked on the substrate 1. The light-emitting layer 4 includes at least one well barrier unit 41. The well barrier unit 41 includes an AlGaN barrier layer 411 and AlGaN quantum dots 412 stacked on the AlGaN barrier layer 411 and spaced apart from each other.

[0057] Figure 3 It is a flow chart of another method for preparing an ultraviolet light-emitting diode epitaxial wafer that improves luminous efficiency provided by an embodiment of the present disclosure. Please refer to Figure 3 It can be seen that the preparation method of ultraviolet light-emitting diode epitaxial wafers to improve luminous efficiency may include:

[0058] S201: Provide a substrate.

[0059] Alternatively, the substrate may be sapphire (Al) with (0001) crystal orientation. 2 O 3 ) is the substrate.

[0060] S202: Sequentially grow an AlN sublayer, an AlN / AlGaN multi-period stress modulation sublayer and an undoped AlGaN sublayer on the substrate to obtain a buffer layer.

[0061] The buffer layer is configured to include sequentially stacked AlN sub-layers, AlN / AlGaN multi-period stress modulation sub-layers and non-doped AlGaN sub-layers, which can achieve a good transition from the substrate to the n-type AlGaN layer. AlN / AlGaN multi-period stress modulation The modulation sublayer can also effectively release certain stress and improve the crystal quality of the epitaxial material below the n-type AlGaN layer, thereby improving the luminous efficiency of the final ultraviolet light-emitting diode epitaxial wafer.

[0062] It should be noted that the AlN / AlGaN multi-period stress modulation sublayer has a superlattice structure.

[0063] Optionally, step S202 may include:

[0064] The AlN sublayer is grown on the substrate at a growth temperature of 1000-1400°C and a pressure of 50-100mbar. The thickness of the AlN sub-layer is 15 to 40nm; before growing the undoped AlGaN layer, the MOCVD (Metal Organic Chemical The buffer layer (with substrate) is annealed in situ in VaporDeposition (Metal Organic Compound Chemical Vapor Deposition) equipment. The temperature is 1000℃-1200℃, the pressure range is 150Torr-500Torr, and the time is Between 5 minutes and 10 minutes; after the annealing is completed, adjust the temperature of the MOCVD equipment to 1000℃-1200℃, grow an undoped AlGaN layer with a thickness of 0.1 to 3.0 microns, and the growth pressure is between 50Torr and 200Torr. It can be ensured that the crystal quality of the obtained buffer layer is good.

[0065] In an implementation manner provided by the present disclosure, the AlN sub-layer can be grown in sections. The first section of AlN sub-layer is grown at a lower temperature, and then the temperature is raised to grow the second section of AlN on the first section of AlN sub-layer. sublayer. The overall quality of the resulting AlN sublayer can be improved.

[0066] For example, the growth temperature of the first AlN sublayer may be 1100°C, and the growth thickness of the first AlN sublayer may be 500 nm; the growth temperature of the second AlN sublayer may be 1350°C, and the growth thickness of the second AlN sublayer may be 1350°C. The growth thickness is 2 microns, and the growth time is 5000s. The crystal quality of the resulting AlN sublayer can be effectively improved.

[0067] In an implementation provided by the present disclosure, the V / III molar ratio of the second AlN sublayer is 300, and the growth pressure of the second AlN sublayer is 50 mbar. The quality of the resulting AlN sublayer is also better.

[0068] In other implementations provided by the present disclosure, the growth temperature and growth pressure of the AlN / AlGaN multi-period stress modulation sublayer can be 1150°C and 50mbar respectively; the growth temperature and growth pressure of the non-doped AlGaN sublayer can be 1150°C and 50mbar respectively. ℃, 50mbar. This disclosure does not limit this.

[0069] S203: Grow an n-type AlGaN layer on the buffer layer.

[0070] Optionally, the thickness of the n-type AlGaN layer is between 1.0-4.0 microns, the growth temperature is between 1000℃-1200℃, the pressure is between 50Torr and 200Torr, and the Si doping concentration is between 10 18 cm -3 -10 20 cm -3 between. An n-type AlGaN layer with better quality can be obtained.

[0071] In other implementations provided by the present disclosure, the growth temperature of the n-type AlGaN layer, the input amount of the aluminum source, the input amount of ammonia gas, the input amount of the gallium source, and the input amount of the silicon source can be respectively 1100℃, 50sccm, 4000sccm, 150sccm and 10sccm. This disclosure does not limit this.

[0072] S204: Grow at least one well barrier unit on the n-type AlGaN layer to obtain a light-emitting layer. The well barrier unit includes an AlGaN barrier layer and AlGaN quantum dots stacked on the AlGaN barrier layer and spaced apart from each other. Growing each well barrier unit includes: growing an AlGaN barrier layer on the n-type AlGaN layer or well barrier unit; depositing an AlN material layer of 1 to 5 nm on the AlGaN barrier layer; annealing the AlN material layer to make the AlN material The surface of the layer has multiple convex island structures; a gallium source and ammonia gas are introduced into the reaction chamber to react with the multiple island structures to generate multiple AlGaN quantum dots.

[0073] It should be noted that the growth conditions and specific parameters of AlGaN quantum dots in the well barrier unit can be referred to Figure 1 Step S104 in , so no details are given here.

[0074] Optionally, the growth rate of the AlGaN barrier layer is 0.01˜0.2nm / s.

[0075] If the growth rate of the AlGaN barrier layer is within the above range, an AlGaN barrier layer with better quality can be obtained, and the AlN material layer grown on the AlGaN barrier layer can be ensured with better quality.

[0076] Optionally, the thickness of the AlGaN barrier layer is 5 to 15 nm. It can effectively transfer and expand carriers.

[0077] Optionally, the growth temperature of the AlGaN barrier layer is 1000-1200°C, and the growth pressure of the AlGaN barrier layer is 50-200 mbar. The crystal quality of the obtained AlGaN barrier layer can be improved.

[0078] It should be noted that the AlGaN barrier layer may or may not be doped with silicon element. This disclosure does not limit this.

[0079] For example, when the AlGaN barrier layer is doped with silicon element, the doping concentration range of the silicon element in the AlGaN barrier layer is 2×10 17 ~5×10 18 cm -3 . It can effectively provide carriers while ensuring the quality of the AlGaN barrier layer.

[0080] S205: Grow an electron blocking layer on the light-emitting layer.

[0081] Alternatively, the electron blocking layer may be an AlyGa1-yN (0.2<y<0.5) layer. The growth temperature is between 900°C and 1050°C, the growth pressure is between 50Torr and 200Torr, and the growth thickness is between 15nm and 60nm.

[0082] S206: Grow a p-type AlGaN layer on the electron blocking layer.

[0083] Alternatively, the p-type AlGaN layer is grown on the electron blocking layer with a growth temperature of 950°C-1050°C and a growth pressure of 100Torr-600Torr.

[0084] It should be noted that in embodiments of the present disclosure, the epitaxial material may be mainly prepared by MOCVD equipment. Among them, high-purity H 2 (hydrogen) or high purity N 2 (nitrogen) or high purity H 2 and high purity N 2 Mixed gas as carrier gas, high purity NH 3 As the N source, trimethylgallium (TMGa) and triethylgallium (TEGa) are used as the gallium source, silane (SiH4) is used as the N-type dopant, trimethylaluminum (TMAl) is used as the aluminum source, and magnocene (CP 2 Mg) as P-type dopant.

[0085] Figure 4 It is a schematic structural diagram of another ultraviolet light-emitting diode epitaxial wafer that improves luminous efficiency provided by an embodiment of the present disclosure. Figure 4 Mid-UV light-emitting diode epitaxial wafers use Figure 3 The ultraviolet light-emitting diode epitaxial wafer is prepared by the preparation method shown in, refer to Figure 4 It can be seen that the ultraviolet light-emitting diode epitaxial wafer includes a substrate 1 and a buffer layer 2, an n-type AlGaN layer 3, a light-emitting layer 4, an electron blocking layer 6 and a P-type AlGaN layer 5 sequentially stacked on the substrate 1. The light-emitting layer 4 includes at least one The well barrier unit 41 includes an AlGaN barrier layer 411 and AlGaN quantum dots 412 stacked on the AlGaN barrier layer 411 and spaced apart from each other. The buffer layer 2 includes an AlN sub-layer 21, an AlN / AlGaN multi-period stress modulation sub-layer 22 and a non-doped AlGaN sub-layer 23 that are sequentially stacked on the substrate.

[0086] Alternatively, the substrate 1 may be a sapphire substrate.

[0087] Alternatively, the N-type dopant in the n-type AlGaN layer 3 may be Si, and the doping concentration may be 10 18 cm -3 -10 20 cm -3 .

[0088] Optionally, the light-emitting layer 4 includes several alternately grown quantum barrier layers and quantum well layers. The quantum well layer may be a GaN layer, and the quantum barrier layer may be an AlxGa1-xN (0<x<0.3) layer.

[0089] Alternatively, the electron blocking layer 6 may be an AlyGa1-yN (0.2<y<0.5) layer.

[0090] Alternatively, the electron blocking layer 6 may be a P-type electron blocking layer, the P-type dopant may be Mg, and the doping concentration may be 10 16 cm -3 -10 18 cm -3 . The P-type electron blocking layer can further increase the hole concentration of the P-type semiconductor layer.

[0091] Optionally, the P-type dopant in the p-type AlGaN layer 5 can be Mg, and the doping concentration is 10 17 cm -3 -10 18 cm -3 .

[0092] Figure 4 The epitaxial wafer structure shown in is relatively Figure 2 The epitaxial wafer structure shown in adds an electron blocking layer and adjusts the structure of the buffer layer, which can improve the crystal quality of the resulting epitaxial wafer. In other implementations provided by the present disclosure, the buffer layer may also adopt a structure similar to the stacking of AlN sublayers and GaN sublayers, and the present disclosure does not limit this.

[0093] The above does not limit the present disclosure in any form. Although the present disclosure has been disclosed through the embodiments, it is not used to limit the present disclosure. Any skilled person familiar with the art, without departing from the scope of the technical solution of the present disclosure, When the technology disclosed above is available, It is allowed to make some changes or modifications into equivalent embodiments with equivalent changes. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the disclosure without departing from the content of the technical solution of the disclosure will still be regarded as the equivalent embodiments. It falls within the scope of the technical solution of this disclosure.

Claims

1. A method for preparing an ultraviolet light-emitting diode epitaxial wafer with improved luminous efficiency, characterized in that: The method for preparing an ultraviolet light-emitting diode epitaxial wafer with improved luminous efficiency comprises: providing a substrate; growing a buffer layer on the substrate; growing an n-type AlGaN layer on the buffer layer; Growing at least one well barrier unit on the n-type AlGaN layer to obtain a light-emitting layer, wherein the well barrier unit includes an AlGaN barrier layer and AlGaN quantum dots stacked on the AlGaN barrier layer and spaced from each other; growing a p-type AlGaN layer on the light-emitting layer; Growing each of the well barrier units, comprising: Growing an AlGaN barrier layer on the n-type AlGaN layer or the well barrier unit; Depositing a 1-5 nm AlN material layer on the AlGaN barrier layer; Annealing the AlN material layer so that a surface of the AlN material layer has a plurality of protruding island structures; A gallium source and ammonia are introduced into the reaction chamber to react with the plurality of island structures to generate a plurality of AlGaN quantum dots.

2. The method for preparing an ultraviolet light-emitting diode epitaxial wafer with improved luminous efficiency according to claim 1, characterized in that: The deposition rate of the AlN material layer is 0.1 nm / s to 1 nm / s.

3. The method for preparing an ultraviolet light-emitting diode epitaxial wafer with improved luminous efficiency according to claim 1, characterized in that: The annealing temperature of the AlN material layer is 1000-1200° C., and the annealing time of the AlN material layer is 800-1000 s.

4. The method for preparing an ultraviolet light-emitting diode epitaxial wafer with improved luminous efficiency according to any one of claims 1 to 3, characterized in that: The V / III molar ratio of the gallium source and the ammonia gas introduced into the reaction chamber is (100-2000):

1.

5. The method for preparing an ultraviolet light-emitting diode epitaxial wafer with improved luminous efficiency according to any one of claims 1 to 3, characterized in that: The stacking density of the plurality of AlGaN quantum dots on the AlGaN barrier layer is 1 to 6×10 11 cm -2 .

6. The method for preparing an ultraviolet light emitting diode epitaxial wafer with improved luminous efficiency according to any one of claims 1 to 3, characterized in that: The diameter of each AlGaN quantum dot is 1-5 nm.

7. The method for preparing an ultraviolet light-emitting diode epitaxial wafer with improved luminous efficiency according to any one of claims 1 to 3, characterized in that: The growth rate of the AlGaN barrier layer is 0.01-0.2 nm / s.

8. The method for preparing an ultraviolet light emitting diode epitaxial wafer with improved luminous efficiency according to any one of claims 1 to 3, characterized in that: The thickness of the AlGaN barrier layer is 5-15 nm.

9. The method for preparing an ultraviolet light-emitting diode epitaxial wafer with improved luminous efficiency according to any one of claims 1 to 3, characterized in that: The growth temperature of the AlGaN barrier layer is 1000-1200° C., and the growth pressure of the AlGaN barrier layer is 50-200 mbar.

10. The method for preparing an ultraviolet light emitting diode epitaxial wafer with improved luminous efficiency according to any one of claims 1 to 3, characterized in that: The step of growing a buffer layer on the substrate comprises: An AlN sublayer, an AlN / AlGaN multi-period stress modulation sublayer and a non-doped AlGaN sublayer are sequentially grown on the substrate to obtain the buffer layer.

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