Deep ultraviolet light-emitting diode epitaxial wafer, its preparation method, and light-emitting diode

Abstract

The present invention discloses a deep ultraviolet light-emitting diode epitaxial wafer, a method for preparing the same, and a light-emitting diode, relating to the field of semiconductor optoelectronic devices. The deep ultraviolet light-emitting diode epitaxial wafer comprises a substrate and a buffer layer, an undoped AlGaN layer, an N-type AlGaN layer, a multi-quantum well layer, an electron blocking layer, a P-type AlGaN layer, and a P-type contact layer sequentially deposited on the substrate. The buffer layer comprises a first AlN layer, a second AlN layer, and an AlGaN layer sequentially deposited on the substrate, with the second AlN layer having multiple In vacancies. The second AlN layer is deposited by depositing an InAlN layer on the first AlN layer, followed by annealing to decompose the InN in the InAlN layer to form In vacancies, with the deposition temperature of the InAlN layer being lower than the annealing temperature. Implementation of the present invention can effectively improve the luminous efficiency of deep ultraviolet light-emitting diodes.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor optoelectronic devices, and in particular to a deep ultraviolet light-emitting diode epitaxial wafer and a preparation method thereof, and a light-emitting diode. Background Art

[0002] AlGaN deep-ultraviolet (DUV) LEDs face two major challenges that severely limit their luminous efficiency. First, when depositing an AlN or AlGaN epitaxial layer on a foreign substrate, the large lattice mismatch between the AlN or AlGaN epitaxial layer and the foreign substrate causes excessive stress in the epitaxial layer, leading to fractures at a certain thickness. Second, poor crystal quality of the AlN or AlGaN layer results in a high dislocation density in the UV LED epitaxial layer, significantly reducing the internal quantum efficiency of the LED and severely diminishing its luminous efficiency. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a deep ultraviolet light-emitting diode epitaxial wafer and a preparation method thereof, which can effectively alleviate the lattice mismatch and thermal mismatch between the substrate and the AlGaN material and improve the luminous efficiency.

[0004] Another technical problem to be solved by the present invention is to provide a deep ultraviolet light emitting diode with high luminous efficiency.

[0005] In order to solve the above problems, the present invention discloses a deep ultraviolet light-emitting diode epitaxial wafer, which includes a substrate and a buffer layer, an undoped AlGaN layer, an N-type AlGaN layer, a multi-quantum well layer, an electron blocking layer, a P-type AlGaN layer and a P-type contact layer sequentially deposited on the substrate; wherein the buffer layer includes a first AlN layer, a second AlN layer and an AlGaN layer sequentially deposited on the substrate, and a plurality of In vacancies are provided on the second AlN layer;

[0006] The deposition method of the second AlN layer is: depositing an InAlN layer on the first AlN layer, and then annealing to decompose InN in the InAlN layer to form In vacancies, and the deposition temperature of the InAlN layer is lower than the annealing temperature.

[0007] As an improvement to the above technical solution, the ratio of In component in the InAlN layer is 0.01-0.1, and the deposition temperature is 700-900°C;

[0008] The annealing temperature of the InAlN layer is 1000-1200°C.

[0009] As an improvement of the above technical solution, the thickness of the first AlN layer is 5-50 nm, the thickness of the InAlN layer is 10-100 nm, and the thickness of the AlGaN layer is 10-100 nm.

[0010] As an improvement of the above technical solution, the Al component ratio in the AlGaN layer is 0.1-1, and the Al component ratio gradually decreases along the deposition direction of the epitaxial wafer.

[0011] As an improvement to the above technical solution, it further includes a third AlN layer deposited between the second AlN layer and the AlGaN layer;

[0012] The deposition temperature of the third AlN layer is greater than the deposition temperature of the first AlN layer and the AlInN layer.

[0013] As an improvement of the above technical solution, the deposition temperature of the first AlN layer is 700-900°C, and the deposition temperature of the third AlN layer is 900-1100°C.

[0014] Correspondingly, the present invention also discloses a method for preparing a deep ultraviolet light-emitting diode epitaxial wafer, which is used to prepare the above-mentioned deep ultraviolet light-emitting diode epitaxial wafer, and comprises:

[0015] Providing a substrate, and sequentially depositing a buffer layer, an undoped AlGaN layer, an N-type AlGaN layer, a multi-quantum well layer, an electron blocking layer, a P-type AlGaN layer, and a P-type contact layer on the substrate;

[0016] wherein, the buffer layer comprises a first AlN layer, a second AlN layer and an AlGaN layer sequentially deposited on the substrate, and a plurality of In vacancies are provided on the second AlN layer;

[0017] The deposition method of the second AlN layer is: depositing an InAlN layer on the first AlN layer, and then annealing to decompose InN in the InAlN layer to form In vacancies, and the deposition temperature of the InAlN layer is lower than the annealing temperature.

[0018] As an improvement of the above technical solution, the deposition pressure of the buffer layer is 50-300 torr, and the deposition atmosphere is a mixed gas of N2 and NH3; wherein the volume ratio of N2 and NH3 is (1-8):1.

[0019] As an improvement of the above technical solution, the InAlN layer is annealed in a nitrogen atmosphere.

[0020] Correspondingly, the present invention also discloses a deep ultraviolet light emitting diode, comprising the above-mentioned deep ultraviolet light emitting diode epitaxial wafer.

[0021] The implementation of the present invention has the following beneficial effects:

[0022] The deep ultraviolet light-emitting diode epitaxial wafer of the present invention has a buffer layer deposited between the epitaxial structure and the substrate. Specifically, the buffer layer structure includes a first AlN layer, a second AlN layer and an AlGaN layer, and a plurality of In vacancies are provided on the second AlN layer. First, through the buffer layer of this structure, the lattice mismatch between the substrate and the AlGaN epitaxial structure is reduced, the dislocation density is reduced, and the luminous efficiency is improved. In particular, the second AlN layer provided with In vacancies can induce dislocations to extend along the In vacancies and merge and annihilate, reducing the dislocations extending to the quantum well layer, reducing the non-radiative recombination centers generated by dislocations, and improving the luminous efficiency of the quantum well. Secondly, the buffer layer provides a nucleation center with the same orientation as the substrate, releasing the stress generated by the lattice mismatch between AlGaN and the substrate, providing a flat nucleation surface for further deposition, reducing the contact angle of its nucleation deposition, so that the island-shaped deposited AlGaN grains can be connected into a surface within a smaller thickness, transforming into a two-dimensional epitaxial deposition, and also effectively improving the luminous efficiency of the deep ultraviolet light-emitting diode. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 1 is a schematic structural diagram of a deep ultraviolet light-emitting diode epitaxial wafer in one embodiment of the present invention;

[0024] Figure 2 is a schematic structural diagram of a buffer layer in one embodiment of the present invention;

[0025] Figure 3 is a schematic structural diagram of a buffer layer in another embodiment of the present invention;

[0026] Figure 4 This is a flow chart of a method for preparing a deep ultraviolet light-emitting diode epitaxial wafer in one embodiment of the present invention. DETAILED DESCRIPTION

[0027] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is described in further detail below.

[0028] refer to Figure 1 and Figure 2The present invention discloses a deep ultraviolet light-emitting diode epitaxial wafer, comprising a substrate 1 and a buffer layer 2, a non-doped AlGaN layer 3, an N-type AlGaN layer 4, a multi-quantum well layer 5, an electron blocking layer 6, a P-type AlGaN layer 7 and a P-type contact layer 8 sequentially deposited on the substrate 1. The buffer layer comprises a first AlN layer 21, a second AlN layer 22 and an AlGaN layer 23 sequentially deposited on the substrate 1. Based on this buffer layer structure, the lattice mismatch between the substrate and the AlGaN epitaxial structure is reduced, the dislocation density is reduced, and the luminous efficiency is improved. In particular, the second AlN layer 22 provided with In vacancies can induce dislocations to extend along the In vacancies and fuse and annihilate, reducing dislocations extending to the quantum well layer, reducing the non-radiative recombination centers generated by dislocations, and improving the luminous efficiency of the quantum well. Secondly, the buffer layer 2 provides a nucleation center with the same orientation as the substrate, which releases the stress caused by the lattice mismatch between AlGaN and the substrate, provides a flat nucleation surface for further deposition, reduces the contact angle of its nucleation deposition, and enables the island-deposited AlGaN grains to be connected into a surface within a smaller thickness, transforming it into a two-dimensional epitaxial deposition, which also effectively improves the luminous efficiency of the deep ultraviolet light-emitting diode.

[0029] The thickness of the first AlN layer 21 is 2-60 nm, and the deposition temperature is 650-950° C. The deposition temperature of the first AlN layer 21 is relatively low. If its thickness exceeds 60 nm, the AlN crystal quality in the first AlN layer 21 is poor. If its thickness is less than 2 nm, the crystal quality of the subsequently deposited second AlN layer 22 is poor, making it difficult to annihilate dislocations. Preferably, the thickness of the first AlN layer 21 is 5-50 nm, and exemplary thicknesses are 6 nm, 10 nm, 15 nm, 22 nm, 30 nm, 38 nm, or 44 nm, but are not limited thereto.

[0030] Among them, the deposition method of the second AlN layer 22 is: depositing an InAlN layer on the first AlN layer 21, and then annealing to decompose the InN in the InAlN layer to form In vacancies, wherein the deposition temperature of the InAlN layer is less than the annealing temperature. It should be noted that since the decomposition temperature of InN is much lower than the decomposition temperature of AlN, after high-temperature treatment, InN decomposes, and In atoms are desorbed from the AlN layer to form In vacancies. Specifically, the deposition temperature of the InAlN layer is 650-950°C, preferably 700-900°C. The annealing temperature is 900-1200°C, preferably 900-1100°C. Further preferably, annealing is performed in an N2 atmosphere to improve the uniformity of the In vacancy distribution and further enhance its effect of annihilating dislocations.

[0031] The thickness of the InAlN layer is 8-120 nm. When the thickness is less than 120 nm, the In atoms after the decomposition of InN will remain inside the InAlN layer and cannot be desorbed, which increases the lattice mismatch between the first AlN layer 21 and the second AlN layer 22. When the thickness of the InAlN layer is less than 8 nm, fewer In vacancies are formed, making it difficult to effectively annihilate dislocations. Preferably, the thickness of the InAlN layer is 10-100 nm, exemplified by 15 nm, 23 nm, 28 nm, 35 nm, 43 nm, 52 nm, 68 nm, 74 nm, or 85 nm, but not limited thereto.

[0032] The ratio of In component in the InAlN layer is 0.01-0.15, exemplified by 0.03, 0.08, 0.1, 0.11, 0.13 or 0.15, but not limited thereto. Preferably, the ratio of In component in the InAlN layer is 0.01-0.1.

[0033] The AlGaN layer 23 can further alleviate the lattice mismatch between the first AlN layer 21, the second AlN layer 22, and the AlGaN-based epitaxial structure, thereby improving luminous efficiency. Specifically, the thickness of the AlGaN layer 23 is 5-120 nm, with exemplary thicknesses being 10 nm, 20 nm, 45 nm, 55 nm, 70 nm, 88 nm, 100 nm, or 105 nm.

[0034] Specifically, the Al component ratio in the AlGaN layer 23 is 0.1-1, and is exemplarily 0.2, 0.4, 0.5, 0.7, or 0.8, but is not limited thereto. Preferably, in one embodiment of the present invention, the Al component ratio gradually decreases along the deposition direction of the epitaxial wafer. Based on this composition control, the lattice mismatch between the buffer layer 2 and the AlGaN-based epitaxial structure can be further reduced.

[0035] Preferably, reference Figure 3In one embodiment of the present invention, the buffer layer 2 further includes a third AlN layer 24, which is deposited between the second AlN layer 22 and the AlGaN layer 23. The deposition temperature of the third AlN layer 25 is higher than that of the first AlN layer 21 and the second AlN layer 22. By introducing the third AlN layer, the thermal stress caused by the thermal expansion coefficient can be alleviated, and the luminous efficiency of the deep ultraviolet light-emitting diode can be further improved. Specifically, the deposition temperature of the third AlN layer 24 is 900-1100°C, and exemplarily 910°C, 925°C, 940°C, 955°C, 970°C or 980°C, but not limited thereto. The thickness of the third AlN layer 24 is 5-50nm. When its thickness is greater than 50nm, it is easy for the compressive stress to be too high and cause the epitaxial layer to break; when its thickness is less than 5nm, it is difficult to effectively buffer the thermal stress. Exemplarily, the thickness of the third AlN layer 25 is 8 nm, 12 nm, 16 nm, 20 nm, 30 nm, 38 nm, 40 nm, or 45 nm, but is not limited thereto.

[0036] The substrate 1 may be a sapphire substrate, a silicon substrate, or a silicon carbide substrate, but is not limited thereto, and is preferably a sapphire substrate.

[0037] Among them, the undoped AlGaN layer 3 can form a central island deposition, providing a good foundation for the subsequent layer to be converted to a two-dimensional deposition. As the thickness of AlGaN increases, the compressive stress will be released through stacking faults, the line defects will be reduced, the crystal quality will be improved, and the reverse leakage will be reduced. However, increasing the thickness of the AlGaN layer consumes a large amount of MO source (metal organic source) material, which greatly increases the epitaxial cost of the light-emitting diode. Therefore, the thickness of the undoped AlGaN layer 3 is controlled to be 2-3μm, exemplarily 2.2μm, 2.4μm, 2.6μm or 2.8μm, but not limited thereto.

[0038] The N-type AlGaN layer 4 can provide electrons, which then recombine with holes in the multi-quantum well layer 5 to emit light. Specifically, the doping element in the N-type AlGaN layer 4 is Si, but not limited thereto. The doping concentration of Si in the N-type AlGaN layer 4 is 1×10 19 -5×10 20 cm -3 , for example 2×10 19 cm -3 , 6×10 19 cm -3 , 1.5×10 20 cm -3 , 2.3×10 20 cm -3 , 3.5×10 20 cm -3 or 4.3 × 10 20 cm -3Specifically, the thickness of the N-type AlGaN layer 4 is 1-5 μm, and exemplarily is 1.5 μm, 1.8 μm, 2.4 μm, 2.8 μm, 3 μm, 3.5 μm, 4 μm, 4.2 μm or 4.6 μm, but not limited thereto.

[0039] Among them, the multi-quantum well layer 5 is an alternately stacked Al x Ga 1-x N quantum well layer and Al y Ga 1-y N quantum barrier layers, stacking period number 6-12. Single Al x Ga 1-x The thickness of the N quantum well layer is 2-5nm, and x is 0.2-0.6. y Ga 1-y The thickness of the N quantum barrier layer is 5-15 nm, and y is 0.4-0.8.

[0040] The electron blocking layer 6 can effectively limit the electron overflow, reduce the blocking of holes, improve the injection efficiency of holes into the quantum well, reduce the carrier Auger recombination, and improve the luminous efficiency of the ultraviolet light emitting diode. a Ga 1-a N layer, but not limited thereto. Specifically, the thickness of the electron blocking layer 6 is 10-50nm, Al a Ga 1-a In the N layer, a is 0.4-0.8.

[0041] The doping element of the P-type AlGaN layer 7 is Mg, but not limited thereto. The doping concentration of Mg in the P-type AlGaN layer 7 is 1×10 19 -5×10 20 cm -3 , the thickness of the P-type AlGaN layer 7 is 100-200 nm.

[0042] The P-type contact layer 8 is a high-doping AlGaN layer. Specifically, the Mg doping concentration in the P-type contact layer 8 is 5×10 19 -5×10 20 cm -3 , the thickness of the P-type contact layer 8 is 10-50nm.

[0043] Accordingly, reference Figure 4 The present invention also discloses a method for preparing a deep ultraviolet light-emitting diode epitaxial wafer, which is used to prepare the above-mentioned deep ultraviolet light-emitting diode epitaxial wafer, and comprises the following steps:

[0044] S1: providing a substrate;

[0045] Specifically, the substrate is a sapphire substrate, a silicon substrate, or a silicon carbide substrate, but is not limited thereto. Preferably, the substrate is a sapphire substrate, which is widely used, low in cost, easy to clean, and has good stability at high temperatures.

[0046] S2: depositing a buffer layer, an undoped AlGaN layer, an N-type AlGaN layer, a multi-quantum well layer, an electron blocking layer, a P-type AlGaN layer and a P-type contact layer on the substrate in sequence;

[0047] Specifically, S2 includes:

[0048] S21: depositing a buffer layer on the substrate;

[0049] Specifically, S21 includes:

[0050] S211: depositing a first AlN layer on the substrate;

[0051] The first AlN layer can be deposited by PVD or MOCVD, but is not limited thereto. Preferably, in one embodiment of the present invention, the first AlN layer is deposited by MOCVD, and the deposition temperature is 650-950°C, preferably 700-900°C, and the deposition pressure is 50-300 torr. The atmosphere during the deposition process is a mixed gas of N2 and NH3, and the volume ratio of N2 to NH3 is (1-10):1, exemplarily 2:1, 3.5:1, 5:1, 7.5:1 or 9:1, but is not limited thereto. Preferably, it is (1-8):1.

[0052] S212: depositing an AlInN layer on the first AlN layer;

[0053] Specifically, in one embodiment of the present invention, an AlInN layer is deposited using MOCVD at a deposition temperature of 650-950°C, preferably 700-900°C, and a deposition pressure of 50-300 Torr. The deposition atmosphere is a mixture of N2 and NH3, with a volume ratio of N2 to NH3 of (1-10):1, exemplified by, but not limited to, 2:1, 3.5:1, 5:1, 7.5:1, or 9:1. A preferred ratio is (1-8):1.

[0054] S213: annealing the substrate obtained in step S212 to form a second AlN layer;

[0055] Specifically, the annealing process is performed at a pressure of 50-300 torr and a temperature of 900-1200° C., preferably 900-1000° C. More preferably, the annealing process is performed under a nitrogen atmosphere.

[0056] S214: depositing a third AlN layer on the second AlN layer;

[0057] The third AlN layer can be deposited by PVD or MOCVD, but is not limited thereto. Preferably, in one embodiment of the present invention, the third AlN layer is deposited by MOCVD, and the deposition temperature is 900-1100°C and the deposition pressure is 50-300 torr. The atmosphere during the deposition process is a mixed gas of N2 and NH3, and the volume ratio of N2 to NH3 is (1-10):1, exemplarily 2:1, 3.5:1, 5:1, 7.5:1 or 9:1, but is not limited thereto. Preferably, it is (1-8):1.

[0058] S215: depositing an AlGaN layer on the third AlN layer;

[0059] Specifically, as an improvement to the above technical solution, the AlGaN layer is deposited using MOCVD at a deposition temperature of 1000-1200°C and a deposition pressure of 50-300 Torr. During the deposition process, the atmosphere is a mixture of N2 and NH3, with a volume ratio of N2 to NH3 of (1-10):1, exemplified by, but not limited to, 2:1, 3.5:1, 5:1, 7.5:1, or 9:1. A preferred ratio is (1-8):1.

[0060] S22: depositing a non-doped AlGaN layer on the AlGaN layer;

[0061] Specifically, in one embodiment of the present invention, the undoped AlGaN layer is deposited by MOCVD, with a deposition temperature of 1000-1300° C. and a deposition pressure of 50-500 Torr.

[0062] S23: forming an N-type AlGaN layer on the non-doped AlGaN layer;

[0063] Specifically, in one embodiment of the present invention, MOCVD is used to deposit the N-type AlGaN layer, with a deposition temperature of 1000-1300° C. and a deposition pressure of 50-500 Torr.

[0064] S24: depositing a multi-quantum well layer on the N-type AlGaN layer;

[0065] Specifically, in one embodiment of the present invention, MOCVD is used to periodically deposit multiple Al x Ga 1-x N quantum well layer and Al y Ga 1-y N quantum barrier layers, that is, a multi-quantum well layer is obtained. Among them, Al x Ga 1-x The deposition temperature of the N quantum well layer is 850-950°C and the deposition pressure is 50-300 torr. y Ga 1-yThe deposition temperature of the N quantum barrier layer is 1050-1150° C., and the deposition pressure is 50-300 Torr.

[0066] S25: depositing an electron blocking layer on the multi-quantum well layer;

[0067] Specifically, in one embodiment of the present invention, the electron blocking layer is deposited by MOCVD, with a deposition temperature of 1000-1100° C. and a deposition pressure of 100-300 Torr.

[0068] S26: depositing a P-type AlGaN layer on the electron blocking layer;

[0069] Specifically, in one embodiment of the present invention, the P-type AlGaN layer is deposited by MOCVD, with a deposition temperature of 1000-1100° C. and a deposition pressure of 100-600 Torr.

[0070] S27: depositing a P-type contact layer on the P-type AlGaN layer;

[0071] The P-type contact layer is deposited by MOCVD, with a deposition temperature of 1000-1100° C. and a deposition pressure of 100-600 torr.

[0072] The present invention will be further described below with specific embodiments:

[0073] Example 1

[0074] This embodiment provides a deep ultraviolet light emitting diode epitaxial wafer, referring to Figure 1 、 Figure 2 It includes a substrate 1 and a buffer layer 2, an undoped AlGaN layer 3, an N-type AlGaN layer 4, a multi-quantum well layer 5, an electron blocking layer 6, a P-type AlGaN layer 7 and a P-type contact layer 8 deposited in sequence on the substrate 1.

[0075] Wherein, the substrate 1 is a sapphire substrate.

[0076] The buffer layer 2 includes a first AlN layer 21, a second AlN layer 22, and an AlGaN layer 23, which are sequentially deposited on the substrate 1. The thickness of the first AlN layer is 35 nm. The second AlN layer 22 is deposited by depositing an InAlN layer (50 nm) on the first AlN layer 21, followed by annealing at 1100°C in a nitrogen atmosphere to obtain the second AlN layer 22. The thickness of the AlGaN layer 23 is 65 nm, and the Al content is 0.8, which is maintained constant.

[0077] The thickness of the non-doped AlGaN layer 3 is 2.2 μm, the thickness of the N-type AlGaN layer 4 is 3.2 μm, and the Si doping concentration is 2.5×10 19 cm -3.

[0078] Among them, the multi-quantum well layer is an alternately stacked Al x Ga 1-x N quantum well layer (x = 0.45) and Al y Ga 1-y N quantum barrier layer (y=0.55), the number of stacking periods is 9. Single Al x Ga 1-x The thickness of the N quantum well layer is 3.5nm, and the single Al y Ga 1-y The thickness of the N quantum barrier layer is 11 nm.

[0079] The electron blocking layer 6 is Al a Ga 1-a The thickness of the N layer (a=0.65) is 30 nm. The thickness of the P-type AlGaN layer 7 is 150 nm, and the Mg doping concentration is 5×10 19 cm -3 The P-type contact layer 8 is a P-type doped AlGaN layer with a Mg doping concentration of 1×10 20 cm -3 , with a thickness of 20nm.

[0080] The method for preparing a deep ultraviolet light-emitting diode epitaxial wafer in this embodiment includes the following steps:

[0081] (1) providing a substrate;

[0082] (2) depositing a first AlN layer on the substrate;

[0083] Specifically, the first AlN layer was deposited in MOCVD at a deposition temperature of 820° C., a pressure of 100 torr, and a deposition atmosphere of a mixed gas of N 2 and NH 3 (the volume ratio of the two being 5:1).

[0084] (3) depositing an AlInN layer on the first AlN layer;

[0085] Specifically, the AlInN layer was deposited in MOCVD at a deposition temperature of 820° C., a pressure of 100 torr, and a deposition atmosphere of a mixed gas of N 2 and NH 3 (the volume ratio of the two being 5:1).

[0086] (4) annealing the substrate obtained in step (3) to form a second AlN layer;

[0087] Specifically, the annealing temperature is 1100° C., and the annealing is performed in a nitrogen atmosphere.

[0088] (5) depositing an AlGaN layer on the second AlN layer;

[0089] Specifically, the AlGaN layer was deposited in MOCVD at a deposition temperature of 1100° C., a pressure of 100 torr, and a deposition atmosphere of a mixed gas of N 2 and NH 3 (the volume ratio of the two being 5:1).

[0090] (6) depositing a non-doped AlGaN layer on the AlGaN layer;

[0091] Specifically, the non-doped AlGaN layer is deposited by MOCVD at a deposition temperature of 1200° C. and a deposition pressure of 100 Torr.

[0092] (7) an N-type AlGaN layer on the non-doped AlGaN layer;

[0093] Specifically, the N-type AlGaN layer is deposited by MOCVD at a deposition temperature of 1200° C. and a deposition pressure of 100 Torr.

[0094] (8) depositing a multi-quantum well layer on the N-type AlGaN layer;

[0095] Specifically, MOCVD is used to periodically deposit multiple Al x Ga 1-x N quantum well layer and Al y Ga 1-y N quantum barrier layer. Among them, Al x Ga 1-x The deposition temperature of the N quantum well layer is 900℃ and the deposition pressure is 200torr. y Ga 1-y The deposition temperature of the N quantum barrier layer is 1100°C and the deposition pressure is 200 torr.

[0096] (9) depositing an electron blocking layer on the multi-quantum well layer;

[0097] Specifically, the electron blocking layer is deposited by MOCVD at a deposition temperature of 1050° C. and a deposition pressure of 200 Torr.

[0098] (10) depositing a P-type AlGaN layer on the electron blocking layer;

[0099] Specifically, the P-type AlGaN layer is deposited by MOCVD at a deposition temperature of 1050° C. and a deposition pressure of 300 Torr.

[0100] (11) depositing a P-type contact layer on the P-type AlGaN layer;

[0101] Specifically, the P-type contact layer is deposited by MOCVD at a deposition temperature of 1050° C. and a deposition pressure of 250 Torr.

[0102] Example 2

[0103] This embodiment provides a deep ultraviolet light emitting diode epitaxial wafer, referring to Figure 1 、 Figure 2 It includes a substrate 1 and a buffer layer 2, an undoped AlGaN layer 3, an N-type AlGaN layer 4, a multi-quantum well layer 5, an electron blocking layer 6, a P-type AlGaN layer 7 and a P-type contact layer 8 deposited in sequence on the substrate 1.

[0104] Wherein, the substrate 1 is a sapphire substrate.

[0105] The buffer layer 2 includes a first AlN layer 21, a second AlN layer 22, and an AlGaN layer 23, which are sequentially deposited on the substrate 1. The thickness of the first AlN layer is 35 nm. The second AlN layer 22 is deposited by depositing an InAlN layer (50 nm) on the first AlN layer 21, followed by annealing at 1100°C in a nitrogen atmosphere to obtain the second AlN layer 22. The thickness of the AlGaN layer 23 is 65 nm, and the Al component ratio decreases from 1% to 0.4%.

[0106] The thickness of the non-doped AlGaN layer 3 is 2.2 μm, the thickness of the N-type AlGaN layer 4 is 3.2 μm, and the Si doping concentration is 2.5×10 19 cm -3 .

[0107] Among them, the multi-quantum well layer is an alternately stacked Al x Ga 1-x N quantum well layer (x = 0.45) and Al y Ga 1-y N quantum barrier layer (y=0.55), the number of stacking periods is 9. Single Al x Ga 1-x The thickness of the N quantum well layer is 3.5nm, and the single Al y Ga 1-y The thickness of the N quantum barrier layer is 11 nm.

[0108] The electron blocking layer 6 is Al a Ga 1-a The thickness of the N layer (a=0.65) is 30 nm. The thickness of the P-type AlGaN layer 7 is 150 nm, and the Mg doping concentration is 5×10 19 cm -3 The P-type contact layer 8 is a P-type doped AlGaN layer with a Mg doping concentration of 1×10 20 cm -3 , with a thickness of 20nm.

[0109] The method for preparing a deep ultraviolet light-emitting diode epitaxial wafer in this embodiment includes the following steps:

[0110] (1) providing a substrate;

[0111] (2) depositing a first AlN layer on the substrate;

[0112] Specifically, the first AlN layer was deposited in MOCVD at a deposition temperature of 820° C., a pressure of 100 torr, and a deposition atmosphere of a mixed gas of N 2 and NH 3 (the volume ratio of the two being 5:1).

[0113] (3) depositing an AlInN layer on the first AlN layer;

[0114] Specifically, the AlInN layer was deposited in MOCVD at a deposition temperature of 820° C., a pressure of 100 torr, and a deposition atmosphere of a mixed gas of N 2 and NH 3 (the volume ratio of the two being 5:1).

[0115] (4) annealing the substrate obtained in step (3) to form a second AlN layer;

[0116] Specifically, the annealing temperature is 1100° C., and the annealing is performed in a nitrogen atmosphere.

[0117] (5) depositing an AlGaN layer on the second AlN layer;

[0118] Specifically, the AlGaN layer was deposited in MOCVD at a deposition temperature of 1100° C., a pressure of 100 torr, and a deposition atmosphere of a mixed gas of N 2 and NH 3 (the volume ratio of the two being 5:1).

[0119] (6) depositing a non-doped AlGaN layer on the AlGaN layer;

[0120] Specifically, the non-doped AlGaN layer is deposited by MOCVD at a deposition temperature of 1200° C. and a deposition pressure of 100 Torr.

[0121] (7) an N-type AlGaN layer on the non-doped AlGaN layer;

[0122] Specifically, the N-type AlGaN layer is deposited by MOCVD at a deposition temperature of 1200° C. and a deposition pressure of 100 Torr.

[0123] (8) depositing a multi-quantum well layer on the N-type AlGaN layer;

[0124] Specifically, MOCVD is used to periodically deposit multiple Al x Ga 1-x N quantum well layer and Al y Ga 1-y N quantum barrier layer. Among them, Al x Ga 1-x The deposition temperature of the N quantum well layer is 900℃ and the deposition pressure is 200torr.y Ga 1-y The deposition temperature of the N quantum barrier layer is 1100°C and the deposition pressure is 200 torr.

[0125] (9) depositing an electron blocking layer on the multi-quantum well layer;

[0126] Specifically, the electron blocking layer is deposited by MOCVD at a deposition temperature of 1050° C. and a deposition pressure of 200 Torr.

[0127] (10) depositing a P-type AlGaN layer on the electron blocking layer;

[0128] Specifically, the P-type AlGaN layer is deposited by MOCVD at a deposition temperature of 1050° C. and a deposition pressure of 300 Torr.

[0129] (11) depositing a P-type contact layer on the P-type AlGaN layer;

[0130] Specifically, the P-type contact layer is deposited by MOCVD at a deposition temperature of 1050° C. and a deposition pressure of 250 Torr.

[0131] Example 3

[0132] This embodiment provides a deep ultraviolet light emitting diode epitaxial wafer, referring to Figure 1 、 Figure 3 It includes a substrate 1 and a buffer layer 2, an undoped AlGaN layer 3, an N-type AlGaN layer 4, a multi-quantum well layer 5, an electron blocking layer 6, a P-type AlGaN layer 7 and a P-type contact layer 8 deposited in sequence on the substrate 1.

[0133] Wherein, the substrate 1 is a sapphire substrate.

[0134] The buffer layer 2 includes a first AlN layer 21, a second AlN layer 22, a third AlN layer 24, and an AlGaN layer 23, which are sequentially deposited on the substrate 1. The thickness of the first AlN layer is 35 nm. The deposition method of the second AlN layer 22 is as follows: an InAlN layer (50 nm) is deposited on the first AlN layer 21, and then annealed at 1100°C in a nitrogen atmosphere to obtain the second AlN layer 22. The thickness of the third AlN layer is 20 nm. The thickness of the AlGaN layer 23 is 65 nm, and the Al component ratio decreases from 1% to 0.4%.

[0135] The thickness of the non-doped AlGaN layer 3 is 2.2 μm, the thickness of the N-type AlGaN layer 4 is 3.2 μm, and the Si doping concentration is 2.5×10 19 cm -3 .

[0136] Among them, the multi-quantum well layer is an alternately stacked Al xGa 1-x N quantum well layer (x = 0.45) and Al y Ga 1-y N quantum barrier layer (y=0.55), the number of stacking periods is 9. Single Al x Ga 1-x The thickness of the N quantum well layer is 3.5nm, and the single Al y Ga 1-y The thickness of the N quantum barrier layer is 11 nm.

[0137] The electron blocking layer 6 is Al a Ga 1-a The thickness of the N layer (a=0.65) is 30 nm. The thickness of the P-type AlGaN layer 7 is 150 nm, and the Mg doping concentration is 5×10 19 cm -3 The P-type contact layer 8 is a P-type doped AlGaN layer with a Mg doping concentration of 1×10 20 cm -3 , with a thickness of 20nm.

[0138] The method for preparing a deep ultraviolet light-emitting diode epitaxial wafer in this embodiment includes the following steps:

[0139] (1) providing a substrate;

[0140] (2) depositing a first AlN layer on the substrate;

[0141] Specifically, the first AlN layer was deposited in MOCVD at a deposition temperature of 820° C., a pressure of 100 torr, and a deposition atmosphere of a mixed gas of N 2 and NH 3 (the volume ratio of the two being 5:1).

[0142] (3) depositing an AlInN layer on the first AlN layer;

[0143] Specifically, the AlInN layer was deposited in MOCVD at a deposition temperature of 820° C., a pressure of 100 torr, and a deposition atmosphere of a mixed gas of N 2 and NH 3 (the volume ratio of the two being 5:1).

[0144] (4) annealing the substrate obtained in step (3) to form a second AlN layer;

[0145] Specifically, the annealing temperature is 1100° C., and the annealing is performed in a nitrogen atmosphere.

[0146] (5) depositing a third AlN layer on the second AlN layer;

[0147] Specifically, the third AlN layer was deposited in MOCVD at a deposition temperature of 820° C., a pressure of 100 torr, and a deposition atmosphere of a mixed gas of N 2 and NH 3 (the volume ratio of the two being 5:1).

[0148] (6) depositing an AlGaN layer on the third AlN layer;

[0149] Specifically, the AlGaN layer was deposited in MOCVD at a deposition temperature of 1100° C., a pressure of 100 torr, and a deposition atmosphere of a mixed gas of N 2 and NH 3 (the volume ratio of the two being 5:1).

[0150] (7) depositing a non-doped AlGaN layer on the AlGaN layer;

[0151] Specifically, the non-doped AlGaN layer is deposited by MOCVD at a deposition temperature of 1200° C. and a deposition pressure of 100 Torr.

[0152] (8) an N-type AlGaN layer on the non-doped AlGaN layer;

[0153] Specifically, the N-type AlGaN layer is deposited by MOCVD at a deposition temperature of 1200° C. and a deposition pressure of 100 Torr.

[0154] (9) depositing a multi-quantum well layer on the N-type AlGaN layer;

[0155] Specifically, MOCVD is used to periodically deposit multiple Al x Ga 1-x N quantum well layer and Al y Ga 1-y N quantum barrier layer. Among them, Al x Ga 1-x The deposition temperature of the N quantum well layer is 900℃ and the deposition pressure is 200torr. y Ga 1-y The deposition temperature of the N quantum barrier layer is 1100°C and the deposition pressure is 200 torr.

[0156] (10) depositing an electron blocking layer on the multi-quantum well layer;

[0157] Specifically, the electron blocking layer is deposited by MOCVD at a deposition temperature of 1050° C. and a deposition pressure of 200 Torr.

[0158] (11) depositing a P-type AlGaN layer on the electron blocking layer;

[0159] Specifically, the P-type AlGaN layer is deposited by MOCVD at a deposition temperature of 1050° C. and a deposition pressure of 300 Torr.

[0160] (12) depositing a P-type contact layer on the P-type AlGaN layer;

[0161] Specifically, the P-type contact layer is deposited by MOCVD at a deposition temperature of 1050° C. and a deposition pressure of 250 Torr.

[0162] Comparative Example 1

[0163] The difference between this comparative example and Example 1 is that the buffer layer is only a 100 nm thick AlN layer sputtered by PVD. The rest is the same as Example 1.

[0164] Comparative Example 2

[0165] This comparative example differs from Example 1 in that the buffer layer comprises a first AlN layer and an AlGaN layer stacked sequentially, without a second AlN layer. Accordingly, the preparation method also does not include the steps for preparing the second AlN layer (i.e., steps (3) and (4)). The remainder of the method is the same as Example 1.

[0166] Comparative Example 3

[0167] The difference between this comparative example and Example 1 is that the buffer layer is a first AlN layer and a second AlN layer stacked in sequence, without an AlGaN layer. Accordingly, the preparation step of the AlGaN layer (i.e., step (5)) is also omitted in the preparation method. The rest of the steps are the same as in Example 1.

[0168] Comparative Example 4

[0169] This comparative example differs from Example 1 in that the buffer layer comprises a second AlN layer and an AlGaN layer stacked sequentially, without a first AlN layer. Accordingly, the preparation method also does not include the step of preparing the first AlN layer (i.e., step (2)). The remainder of the method is the same as Example 1.

[0170] Comparative Example 5

[0171] This comparative example differs from Example 1 in that the buffer layer is a second AlN layer, and the first AlN layer and AlGaN layer are not provided. Accordingly, the preparation steps for the first AlN layer and AlGaN layer (i.e., steps (2) and (5)) are not provided in the preparation method, and the rest are the same as in Example 1.

[0172] The brightness of the deep ultraviolet light-emitting diode epitaxial wafers obtained in Examples 1-3 and Comparative Examples 1-5 was tested, and the light efficiency improvement rates of the other examples and comparative examples were calculated based on the epitaxial wafer in Comparative Example 1. The specific results are shown in the following table:

[0173] The specific results are as follows:

[0174]

[0175]

[0176] It can be seen from the table that when the buffer layer of the present invention is introduced into the epitaxial structure, the luminous efficiency can be effectively improved.

[0177] The above is a preferred embodiment of the invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A deep ultraviolet light-emitting diode epitaxial wafer, characterized in that: The invention comprises a substrate and a buffer layer, an undoped AlGaN layer, an N-type AlGaN layer, a multi-quantum well layer, an electron blocking layer, a P-type AlGaN layer and a P-type contact layer sequentially deposited on the substrate; wherein the buffer layer comprises a first AlN layer, a second AlN layer and an AlGaN layer sequentially deposited on the substrate, and a plurality of In vacancies are provided on the second AlN layer; The second AlN layer is deposited by depositing an InAlN layer on the first AlN layer, followed by annealing to decompose InN in the InAlN layer to form In vacancies, wherein the deposition temperature of the InAlN layer is lower than the annealing temperature; The InAlN layer has an In component ratio of 0.01-0.1 and a deposition temperature of 700-900°C. The annealing temperature of the InAlN layer is 1000-1200°C.

2. The deep ultraviolet light-emitting diode epitaxial wafer according to claim 1, wherein: The thickness of the first AlN layer is 5-50 nm, the thickness of the InAlN layer is 10-100 nm, and the thickness of the AlGaN layer is 10-100 nm.

3. The deep ultraviolet light-emitting diode epitaxial wafer according to claim 1, wherein: The Al component ratio in the AlGaN layer is 0.1-1, and the Al component ratio gradually decreases along the deposition direction of the epitaxial wafer.

4. The deep ultraviolet light-emitting diode epitaxial wafer according to any one of claims 1 to 3, wherein: Also comprising a third AlN layer deposited between the second AlN layer and the AlGaN layer; The deposition temperature of the third AlN layer is greater than the deposition temperature of the first AlN layer.

5. The deep ultraviolet light-emitting diode epitaxial wafer according to claim 4, wherein: The deposition temperature of the first AlN layer is 700-900° C., and the deposition temperature of the third AlN layer is 900-1100° C.

6. A method for preparing a deep ultraviolet light-emitting diode epitaxial wafer, for preparing the deep ultraviolet light-emitting diode epitaxial wafer according to any one of claims 1 to 5, characterized in that: include: Providing a substrate, and sequentially depositing a buffer layer, an undoped AlGaN layer, an N-type AlGaN layer, a multi-quantum well layer, an electron blocking layer, a P-type AlGaN layer, and a P-type contact layer on the substrate; The buffer layer comprises a first AlN layer, a second AlN layer and an AlGaN layer sequentially deposited on the substrate, and a plurality of In vacancies are provided on the second AlN layer; The deposition method of the second AlN layer is: depositing an InAlN layer on the first AlN layer, and then annealing to decompose InN in the InAlN layer to form In vacancies, and the deposition temperature of the InAlN layer is lower than the annealing temperature.

7. The method for preparing a deep ultraviolet light-emitting diode epitaxial wafer according to claim 6, wherein: The deposition pressure of the buffer layer is 50-300 torr, and the deposition atmosphere is a mixed gas of N2 and NH3; wherein the volume ratio of N2 to NH3 is (1-8):

1.

8. The method for preparing a deep ultraviolet light-emitting diode epitaxial wafer according to claim 6, wherein: The InAlN layer is annealed in a nitrogen atmosphere.

9. A deep ultraviolet light-emitting diode, characterized in that: It comprises the deep ultraviolet light-emitting diode epitaxial wafer as described in any one of claims 1 to 5.

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