Deep ultraviolet light-emitting diode epitaxial wafers and their fabrication methods, deep ultraviolet light-emitting diodes

Abstract

This invention discloses a deep ultraviolet (DUV) light-emitting diode (LED) epitaxial wafer and its fabrication method, as well as the DUV itself. The DUV epitaxial wafer includes a substrate and, sequentially stacked on the substrate, a buffer layer, a nucleation layer, an undoped AlGaN layer, an N-type AlGaN layer, a multiple quantum well layer, an electron blocking layer, a P-type AlGaN layer, and a P-type contact layer. The nucleation layer includes, sequentially stacked on the buffer layer, a two-dimensional AlGaN nucleation preparation layer, an Al nanodot layer, an AlGa nanocluster nucleation point layer, and an AlGaN nucleation layer. The DUV epitaxial wafer provided by this invention can reduce the dislocation density of the DUV, reduce the nonradiative recombination efficiency of the quantum wells, and improve the luminous efficiency of the DUV.

Description

Technical Field

[0001] This invention relates to the field of optoelectronic technology, and in particular to a deep ultraviolet light-emitting diode epitaxial wafer and its preparation method, and a deep ultraviolet light-emitting diode. Background Technology

[0002] Deep ultraviolet solid-state light sources have wide applications in sterilization, water purification, biochemistry and medicine, high-density optical storage light sources, fluorescence analysis systems and related information sensing.

[0003] Early reports indicated extremely low efficiency for ultraviolet LEDs. At a wavelength of 400 nm, the external quantum efficiency was only 50%, dropping sharply to a mere 0.2% at 250 nm as the wavelength shortened further. This is primarily due to the significant difference in atomic mobility and adhesion coefficient between Al and Ga atoms during the growth of GaN and AlGaN materials. Al atoms have lower mobility and higher adhesion coefficients than Ga atoms, leading to the aggregation and formation of numerous three-dimensional island-like structures during the growth of high-Al Al content AlGaN materials. These islands are difficult to move freely on the surface and grow into a smooth two-dimensional plane, directly and significantly reducing the crystal quality of AlGaN. AlGaN materials also exhibit a high defect density, reaching 10-1. 10 cm -2 -10 11 cm -2 The dislocation density in GaN is relatively low, at 10⁻⁶. 8 cm -2 Such a high dislocation density will turn this region into a nonradiative recombination center, reducing the radiative recombination efficiency in the active region and thus affecting the optoelectronic performance of nitride semiconductor devices. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an epitaxial wafer for a deep ultraviolet light-emitting diode (DUV) that reduces the dislocation density of the DUV, reduces the nonradiative recombination efficiency of the quantum well, and improves the luminous efficiency of the DUV.

[0005] The technical problem to be solved by the present invention is to provide a method for preparing a deep ultraviolet light-emitting diode epitaxial wafer, which has a simple process and can stably produce the above-mentioned deep ultraviolet light-emitting diode epitaxial wafer with good performance.

[0006] To solve the above-mentioned technical problems, the present invention provides a deep ultraviolet light-emitting diode epitaxial wafer, comprising a substrate and a buffer layer, a nucleation layer, an undoped AlGaN layer, an N-type AlGaN layer, a multiple quantum well layer, an electron blocking layer, a P-type AlGaN layer and a P-type contact layer sequentially stacked on the substrate.

[0007] The nucleation layer comprises a two-dimensional AlGaN nucleation preparation layer, an Al nanodot layer, an AlGa nanocluster nucleation dot layer, and an AlGaN nucleation layer, which are sequentially stacked on the buffer layer.

[0008] In one embodiment, the thickness of the two-dimensional AlGaN nucleation preparation layer is 10nm-100nm;

[0009] The thickness of the Al nanodot layer is 5nm-50nm;

[0010] The thickness of the AlGa nanocluster nucleation point layer is 50nm-500nm;

[0011] The thickness of the AlGaN nucleation layer is 0.5μm-5μm.

[0012] In one embodiment, the Al component concentration in the two-dimensional AlGaN nucleation preparation layer is 0.1-1.

[0013] In one embodiment, the Al component concentration in the AlGaN nucleation layer is 0.1-1.

[0014] To address the above problems, this invention provides a method for fabricating a deep ultraviolet light-emitting diode epitaxial wafer, comprising the following steps:

[0015] Prepare the substrate;

[0016] A buffer layer, a nucleation layer, an undoped AlGaN layer, an N-type AlGaN layer, a multiple quantum well layer, an electron blocking layer, a P-type AlGaN layer, and a P-type contact layer are sequentially deposited on the substrate.

[0017] The nucleation layer comprises a two-dimensional AlGaN nucleation preparation layer, an Al nanodot layer, an AlGa nanocluster nucleation dot layer, and an AlGaN nucleation layer, which are sequentially stacked on the buffer layer.

[0018] In one embodiment, depositing the two-dimensional AlGaN nucleation preparation layer on the buffer layer includes the following steps:

[0019] The reaction chamber temperature was controlled at 700℃-1000℃, and the pressure was controlled at 50 torr-300 torr. N2 and NH3 were introduced as carrier gases, and N source, Ga source and Al source were introduced to complete the deposition.

[0020] In one embodiment, depositing the Al nanodot layer on the two-dimensional AlGaN nucleation preparation layer includes the following steps:

[0021] First, control the temperature of the reaction chamber at 900℃-1100℃ and the pressure at 100 torr-500 torr. Then, introduce N2 as a carrier gas and introduce an Al source to complete the deposition.

[0022] In one embodiment, depositing the AlGa nanocluster nucleation point layer on the Al nanodot layer includes the following steps:

[0023] The reaction chamber temperature was controlled at 900℃-1100℃, the pressure at 100 torr-500 torr, N2 was introduced as the carrier gas, and Al and Ga sources were introduced to complete the deposition.

[0024] In one embodiment, depositing the AlGaN nucleation layer on the AlGa nanocluster nucleation point layer includes the following steps:

[0025] The reaction chamber temperature was controlled at 1000℃-1200℃, and the pressure was controlled at 50 torr-300 torr. N2 was introduced as a carrier gas, and N2, NH3 and H2 were introduced as carrier gases. Ga source, Al source and N source were introduced to complete the deposition.

[0026] Accordingly, the present invention also provides a deep ultraviolet light-emitting diode, wherein the deep ultraviolet light-emitting diode includes the deep ultraviolet light-emitting diode epitaxial wafer described above.

[0027] Implementing this invention has the following beneficial effects:

[0028] The present invention grows a nucleation layer on a buffer layer, the nucleation layer comprising a two-dimensional AlGaN nucleation preparation layer, an Al nanodot layer, an AlGa nanocluster nucleation dot layer and an AlGaN nucleation layer sequentially stacked on the buffer layer. The two-dimensional AlGaN nucleation preparation layer provides a flat nucleation surface for the growth of Al nanodot layers, reducing the contact angle of nucleation growth. The Al nanodot layer controls the density of nucleation points, which is closely related to the density of subsequent layered structures. The AlGa nanocluster nucleation layer introduces Ga atoms, enabling the Al nanodot layer to continue growing while reducing lattice mismatch with the subsequent AlGaN nucleation layer, thus improving the crystal quality of the AlGaN nucleation layer. The density of the AlGaN nucleation layer is closely related to the dislocation density of the deep ultraviolet epitaxial layer. The fusion of the AlGaN nucleation layer generates line defects, reducing the crystal quality of the GaN epitaxial layer. However, by depositing the two-dimensional AlGaN nucleation preparation layer, Al nanodot layer, and AlGa nanocluster nucleation layer, the density of the AlGaN nucleation layer can be effectively controlled to control the dislocation density, reduce the defect density, reduce the nonradiative recombination efficiency of the quantum well, and improve the luminous efficiency of the deep ultraviolet light-emitting diode. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of the deep ultraviolet light-emitting diode epitaxial wafer provided by the present invention.

[0030] Among them: substrate 1, buffer layer 2, nucleation layer 3, undoped AlGaN layer 4, N-type AlGaN layer 5, multiple quantum well layer 6, electron blocking layer 7, P-type AlGaN layer 8, P-type contact layer 9, two-dimensional AlGaN nucleation preparation layer 31, Al nanodot layer 32, AlGa nanocluster nucleation point layer 33, AlGaN nucleation layer 34. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in further detail below.

[0032] Unless otherwise stated or in case of contradiction, the terms or phrases used herein shall have the following meanings:

[0033] In this invention, the terms "combinations thereof", "any combination thereof", and "any combination thereof" include all suitable combinations of any two or more of the listed items.

[0034] In this invention, "preferred" is merely a description of a more effective implementation method or embodiment, and should be understood as not constituting a limitation on the scope of protection of this invention.

[0035] In this invention, the technical features described in an open-ended manner include both closed-ended technical solutions composed of the listed features and open-ended technical solutions that include the listed features.

[0036] In this invention, numerical ranges are involved, and unless otherwise specified, they include the two endpoints of the numerical range.

[0037] Traditional nucleation layers consist of numerous three-dimensional island structures. The high nucleation density leads to the formation of a large number of dislocations when the nucleation islands merge, which extend along the epitaxial layer direction to the quantum well and form non-radiative recombination centers, thus reducing the internal quantum efficiency of deep ultraviolet light-emitting diodes.

[0038] To address the above problems, this invention provides a deep ultraviolet light-emitting diode epitaxial wafer, such as... Figure 1 As shown, it includes a substrate 1 and a buffer layer 2, a nucleation layer 3, an undoped AlGaN layer 4, an N-type AlGaN layer 5, a multiple quantum well layer 6, an electron blocking layer 7, a P-type AlGaN layer 8, and a P-type contact layer 9 sequentially stacked on the substrate 1.

[0039] The nucleation layer 3 includes a two-dimensional AlGaN nucleation preparation layer 31, an Al nanodot layer 32, an AlGa nanocluster nucleation dot layer 33, and an AlGaN nucleation layer 34, which are sequentially stacked on the buffer layer 2.

[0040] In one embodiment, the thickness of the two-dimensional AlGaN nucleation preparation layer is 10 nm-100 nm; the thickness of the Al nanodot layer is 5 nm-50 nm; the thickness of the AlGa nanocluster nucleation point layer is 50 nm-500 nm; and the thickness of the AlGaN nucleation layer is 0.5 μm-5 μm. In another embodiment, the Al component concentration in the two-dimensional AlGaN nucleation preparation layer is 0.1-1; and the Al component concentration in the AlGaN nucleation layer is 0.1-1.

[0041] In the nucleation layer of this invention, the two-dimensional AlGaN nucleation preparation layer provides a flat nucleation surface for the growth of the Al nanodot layer, reducing its contact angle for nucleation growth; the Al nanodot layer controls the density of nucleation points, and the nucleation point density of the Al nanodot layer is closely related to the density of the AlGaN nucleation layer; the AlGa nanocluster nucleation point layer introduces Ga atoms, enabling the Al nanodot layer to continue growing, while reducing lattice mismatch with the subsequent AlGaN nucleation layer and improving the crystal quality of the AlGaN nucleation layer; the density of the AlGaN nucleation layer is closely related to the dislocation density of the deep ultraviolet epitaxial layer. The fusion of the AlGaN nucleation layer generates line defects, reducing the crystal quality of the GaN epitaxial layer. However, by depositing the two-dimensional AlGaN nucleation preparation layer, the Al nanodot layer, and the AlGa nanocluster nucleation point layer, the density of the AlGaN nucleation layer can be effectively controlled to control the dislocation density, reduce the defect density, reduce the nonradiative recombination efficiency of the quantum well, and improve the luminous efficiency of the deep ultraviolet light-emitting diode.

[0042] In addition to the nucleation layer described above, the other features of the layered structure of the present invention are as follows:

[0043] In one embodiment, the substrate is selected from one of the following: sapphire substrate, SiO2-sapphire composite substrate, silicon substrate, silicon carbide substrate, gallium nitride substrate, and zinc oxide substrate. Preferably, the substrate is a sapphire substrate, as sapphire is currently the most commonly used substrate material. Sapphire substrates have advantages such as mature manufacturing processes, low price, ease of cleaning and processing, and good stability at high temperatures.

[0044] In one embodiment, the buffer layer is an AlN buffer layer. The AlN buffer layer provides nucleation centers aligned with the substrate, releasing stress caused by lattice mismatch between AlGaN and the substrate, as well as thermal stress caused by thermal expansion coefficient mismatch. Further growth provides a flat nucleation surface, reducing the contact angle of nucleation growth and allowing island-grown GaN grains to connect into a plane within a smaller thickness, transforming into two-dimensional epitaxial growth. This improves the crystal quality of the subsequently deposited AlGaN layer, reduces dislocation density, and increases the radiative recombination efficiency of the multi-quantum-well layer. In one embodiment, the thickness of the buffer layer is 80 nm-150 nm.

[0045] In one embodiment, the growth temperature of the undoped AlGaN layer is 1000℃-1300℃, the growth pressure is 50 torr-500 torr, and the growth thickness is 1μm-5μm. Preferably, the growth temperature of the undoped AlGaN layer is 1200℃, the growth pressure is 100 torr, and the growth thickness is 2μm-3μm. The undoped AlGaN layer has a higher growth temperature and lower pressure, resulting in better GaN crystal quality. Furthermore, as the AlGaN thickness increases, compressive stress is released through stacking faults, reducing line defects, improving crystal quality, and lowering reverse leakage current. However, increasing the AlGaN layer thickness consumes a significant amount of MO source metal-organic source material, greatly increasing the epitaxial cost of the light-emitting diode. Therefore, controlling the thickness to 2μm-3μm not only saves production costs but also ensures that the GaN material has high crystal quality.

[0046] In one embodiment, the N-type AlGaN layer is grown at a temperature of 1000℃-1300℃, and the Si doping concentration is 1*10⁻⁶. 19 atoms / cm 3 -5*10 20 atoms / cm 3 The thickness is 1μm-5μm. Preferably, the growth temperature is 1200℃, the growth pressure is 100 torr, the growth thickness is 2μm-3μm, and the Si doping concentration is 2.5*10⁻⁶. 19 atoms / cm 3 First, the N-type doped AlGaN layer provides sufficient electron-hole recombination for ultraviolet LED emission. Second, the resistivity of the N-type doped AlGaN layer is higher than that of the transparent electrode on the P-type GaN layer; therefore, sufficient Si doping can effectively reduce the resistivity of the N-type GaN layer. Finally, a sufficient thickness of the N-type doped AlGaN layer can effectively relieve stress and improve the luminous efficiency of the LED.

[0047] In one embodiment, the multiple quantum well layers are alternating stacked Al x Ga 1-x N quantum well layer and Al y Ga 1-y N quantum barrier layers, stacked with 3-15 periods. Al x Ga 1-x The N-quantum well layer is grown at a temperature of 950℃-1150℃, with a thickness of 2nm-5nm, a growth pressure of 50 torr-300 torr, and an Al composition of 0.2-0.6%. y Ga 1-yThe growth temperature of the N quantum barrier layer is 1000℃-1300℃, the thickness is 5nm-15nm, the growth pressure is 50torr-300torr, and the Al composition is 0.4-0.8.

[0048] Preferably, the number of stacking cycles is 9, wherein Al x Ga 1-x The N quantum well layer was grown at a temperature of 1050℃, a thickness of 3.5 nm, a pressure of 200 torr, and an Al composition of 0.55. y Ga 1-y The N-quantum barrier layer was grown at a temperature of 1150℃, with a thickness of 11 nm, a growth pressure of 200 torr, and an Al composition of 0.7. Multiple quantum wells are regions where electrons and holes recombine; a well-designed structure can significantly increase the overlap of electron and hole wave functions, thereby improving the luminous efficiency of LED devices.

[0049] In one embodiment, the electron blocking layer is an AlGaN electron blocking layer with a thickness of 10nm-100nm, a growth temperature of 1000℃-1100℃, and a pressure of 100torr-300torr, wherein the Al composition is 0.4-0.8%. Preferably, the AlGaN electron blocking layer has a thickness of 30nm, an Al composition of 0.75%, a growth temperature of 1050℃, and a growth pressure of 200torr. This effectively limits electron overflow and reduces the blocking of holes, improving the hole-to-electron-well injection efficiency, reducing carrier Auger recombination, and improving the luminous efficiency of the light-emitting diode.

[0050] In one embodiment, the growth temperature of the p-type AlGaN layer is 1000℃-1100℃, the thickness is 20nm-200nm, the growth pressure is 100torr-600torr, and the Mg doping concentration is 1*10 19 atoms / cm 3 -5*10 20 atoms / cm 3 .

[0051] Preferably, the p-type AlGaN layer is grown at a temperature of 1050℃, has a thickness of 100 nm, a growth pressure of 200 torr, and a Mg doping concentration of 5*10⁻⁶. 19 atoms / cm 3 Excessive Mg doping concentration can compromise crystal quality, while insufficient doping concentration can affect hole concentration. Meanwhile, the P-type doped AlGaN layer can effectively fill the epitaxial layer, resulting in a smooth-surfaced deep-ultraviolet LED epitaxial wafer.

[0052] In one embodiment, the growth temperature of the P-type contact layer is 900℃-1100℃, the thickness is 5nm-50nm, the growth pressure is 100torr-600torr, and the Mg doping concentration is 5*10. 19 atoms / cm 3 -5*10 20 atoms / cm 3 .

[0053] Preferably, the p-type doped AlGaN layer is grown at a temperature of 950℃, a thickness of 10 nm, a growth pressure of 200 torr, and a Mg doping concentration of 1*10⁻⁶. 20 atoms / cm 3 A highly doped P-type contact layer reduces contact resistance.

[0054] Accordingly, the present invention also provides a method for preparing the above-mentioned deep ultraviolet light-emitting diode epitaxial wafer, comprising the following steps:

[0055] S1. Prepare the substrate;

[0056] S2. Sequentially deposit a buffer layer, a nucleation layer, an undoped AlGaN layer, an N-type AlGaN layer, a multiple quantum well layer, an electron blocking layer, a P-type AlGaN layer, and a P-type contact layer on the substrate.

[0057] The nucleation layer comprises a two-dimensional AlGaN nucleation preparation layer, an Al nanodot layer, an AlGa nanocluster nucleation dot layer, and an AlGaN nucleation layer, which are sequentially stacked on the buffer layer.

[0058] In one implementation, step S2 includes the following steps:

[0059] S21. An AlN buffer layer is deposited on the front side of the substrate in PVD.

[0060] S22. Deposit the two-dimensional AlGaN nucleation preparation layer on the buffer layer:

[0061] The reaction chamber temperature was controlled at 700℃-1000℃, and the pressure was controlled at 50 torr-300 torr. N2 and NH3 were introduced as carrier gases, and N source, Ga source and Al source were introduced to complete the deposition.

[0062] S23. Deposit the Al nanodot layer on the two-dimensional AlGaN nucleation preparation layer:

[0063] First, control the temperature of the reaction chamber at 900℃-1100℃ and the pressure at 100 torr-500 torr. Then, introduce N2 as a carrier gas and introduce an Al source to complete the deposition.

[0064] It should be noted that, in one embodiment, the substrate used in this invention is a PSS substrate, whose deposition direction is mainly the C-plane, and other surfaces of the PSS image are basically not deposited; and because the Al nanolayer is relatively thin, an Al thin film layer is not formed on the substrate, but Al nanodots are obtained instead.

[0065] S24. Deposit the AlGa nanocluster nucleation point layer on the Al nanodot layer:

[0066] The reaction chamber temperature was controlled at 900℃-1100℃, the pressure at 100 torr-500 torr, N2 was introduced as the carrier gas, and Al and Ga sources were introduced to complete the deposition.

[0067] It should be noted that as the Al nanodot layer continues to deposit the AlGa nanocluster layer, the Al nanodot layer acts as a nucleus, and the AlGa nanocluster layer continues to grow. Depending on the epitaxial growth conditions, such as high pressure, the AlGa nanocluster layer is promoted to grow in three dimensions. Therefore, the subsequent deposition results in AlGa nanocluster nucleation sites.

[0068] S25. Deposit the AlGaN nucleation layer on the AlGa nanocluster nucleation point layer:

[0069] The reaction chamber temperature was controlled at 1000℃-1200℃, and the pressure was controlled at 50 torr-300 torr. N2 was introduced as a carrier gas, and N2, NH3 and H2 were introduced as carrier gases. Ga source, Al source and N source were introduced to complete the deposition.

[0070] S26. Deposit the undoped AlGaN layer on the AlGaN nucleation layer:

[0071] The reaction chamber temperature was controlled at 1000℃-1300℃, the growth pressure at 50 torr-500 torr, and N source, Ga source and Al source were introduced to complete the deposition.

[0072] S27. Deposit the N-type AlGaN layer on the undoped AlGaN layer:

[0073] The reaction chamber temperature was controlled at 1000℃-1300℃, the pressure at 50 torr-300 torr, and Si, Al, N and Ga sources were introduced to complete the deposition.

[0074] S28. Deposit the multi-quantum-well layer on the N-type AlGaN layer:

[0075] First, control the temperature of the reaction chamber at 950℃-1150℃ and the pressure at 50 torr-300 torr, then introduce N source, Ga source and Al source to complete Al production. x Ga 1-xAfter depositing an N quantum well layer, the temperature is controlled at 1000℃-1300℃, and N, Ga, and Al sources are continuously introduced to complete the Al deposition process. y Ga 1-y Nitrogen deposition, repeated in 3-15 cycles.

[0076] S29. Deposit the electron blocking layer on the multi-quantum-well layer:

[0077] The reaction chamber temperature was controlled at 1000℃-1100℃ and the pressure at 100 torr-300 torr. N source, Ga source and Al source were introduced to complete the deposition of AlGaN layer.

[0078] S30. Deposit the P-type AlGaN layer and the P-type contact layer on the electron blocking layer:

[0079] The reaction chamber temperature was controlled at 1000℃-1100℃ and the pressure at 100 torr-600 torr. Mg, N, Ga and Al sources were introduced to complete the deposition of the P-type AlGaN layer. Then, the reaction chamber temperature was controlled at 900℃-1100℃ and the pressure at 100 torr-600 torr. Mg, N, Ga and Al sources were introduced to complete the deposition of the P-type AlGaN contact layer.

[0080] Accordingly, the present invention also provides a deep ultraviolet light-emitting diode, wherein the deep ultraviolet light-emitting diode includes the deep ultraviolet light-emitting diode epitaxial wafer described above.

[0081] The deposition process is completed using MOCVD, CVD, or PVD equipment. This invention does not limit the deposition method. High-purity N2 (nitrogen) and H2 (hydrogen) are used as carrier gases. High-purity NH3 (ammonia) provides the N (nitrogen) source. TMAl (trimethylaluminum) is used as the aluminum source, and Cp2Mg (magnesium dicerene) is used as the magnesium source. TMGa (trimethylgallium) and TEGa (triethylgallium) are used as gallium sources, respectively. Silane (SiH4) is used as the N-type dopant, but the methods are not limited to those listed above.

[0082] The present invention is further illustrated below with specific embodiments:

[0083] Example 1

[0084] This embodiment provides a deep ultraviolet light-emitting diode epitaxial wafer, including a substrate and a buffer layer, a nucleation layer, an undoped AlGaN layer, an N-type AlGaN layer, a multiple quantum well layer, an electron blocking layer, a P-type AlGaN layer and a P-type contact layer sequentially stacked on the substrate.

[0085] The nucleation layer comprises a two-dimensional AlGaN nucleation preparation layer, an Al nanodot layer, an AlGa nanocluster nucleation dot layer, and an AlGaN nucleation layer, which are sequentially stacked on the buffer layer.

[0086] The thickness of the two-dimensional AlGaN nucleation preparation layer is 50 nm, the thickness of the Al nanodot layer is 20 nm, the thickness of the AlGa nanocluster nucleation dot layer is 350 nm, and the thickness of the AlGaN nucleation layer is 1.9 μm.

[0087] The Al component concentration in the two-dimensional AlGaN nucleation preparation layer is 0.5, and the Al component concentration in the AlGaN nucleation layer is 0.45.

[0088] The above-mentioned method for fabricating deep ultraviolet light-emitting diode epitaxial wafers includes the following steps:

[0089] S1. Prepare the substrate;

[0090] S2. Sequentially deposit a buffer layer, a nucleation layer, an undoped AlGaN layer, an N-type AlGaN layer, a multiple quantum well layer, an electron blocking layer, a P-type AlGaN layer, and a P-type contact layer on the substrate.

[0091] Step S2 includes the following steps:

[0092] S21. An AlN buffer layer is deposited on the front side of the substrate in PVD.

[0093] S22. Deposit the two-dimensional AlGaN nucleation preparation layer on the buffer layer:

[0094] The reaction chamber temperature was controlled at 820℃ and the pressure at 100 torr. N2 and NH3 were introduced as carrier gases, and N source, Ga source and Al source were introduced to complete the deposition.

[0095] S23. Deposit the Al nanodot layer on the two-dimensional AlGaN nucleation preparation layer:

[0096] First, control the temperature of the reaction chamber at 980℃ and the pressure at 300 torr, introduce N2 as a carrier gas, and introduce the Al source to complete the deposition.

[0097] S24. Deposit the AlGa nanocluster nucleation point layer on the Al nanodot layer:

[0098] The reaction chamber temperature was controlled at 980℃ and the pressure at 300 torr. N2 was introduced as the carrier gas, and Al and Ga sources were introduced to complete the deposition.

[0099] S25. Deposit the AlGaN nucleation layer on the AlGa nanocluster nucleation point layer:

[0100] The reaction chamber temperature was controlled at 1050℃ and the pressure at 150 torr. N2 was introduced as a carrier gas, and N2, NH3 and H2 were introduced as carrier gases. Ga source, Al source and N source were introduced to complete the deposition.

[0101] S26. Deposit the undoped AlGaN layer on the AlGaN nucleation layer:

[0102] The reaction chamber temperature was controlled at 1200℃, the growth pressure at 100 torr, and N, Ga, and Al sources were introduced to complete the deposition and control the thickness at 2.5 μm.

[0103] S27. Deposit the N-type AlGaN layer on the undoped AlGaN layer:

[0104] The reaction chamber temperature was controlled at 1200℃ and the pressure at 100 torr. Si, Al, N and Ga sources were introduced to complete the deposition and control the thickness to 2.5 μm.

[0105] S28. Deposit the multi-quantum-well layer on the N-type AlGaN layer:

[0106] First, control the reaction chamber temperature at 1150℃ and the pressure at 200 torr, then introduce N source, Ga source and Al source to complete Al production. x Ga 1-x An N quantum well layer was deposited and its thickness was controlled to be 3.5 nm, with an Al composition of 0.55. The temperature was then controlled at 1150 °C, and the growth pressure at 200 torr. N, Ga, and Al sources were then introduced to complete the Al deposition process. y Ga 1-y Nitrogen was deposited and the thickness was controlled to be 11 nm, with an Al composition of 0.7; the layers were stacked repeatedly for 9 cycles.

[0107] S29. Deposit the electron blocking layer on the multi-quantum-well layer:

[0108] The reaction chamber temperature was controlled at 1050℃ and the pressure at 200 torr. N source, Ga source and Al source were introduced to complete the deposition of AlGaN layer and control the thickness to 30nm. The Al composition was 0.75.

[0109] S30. Deposit the P-type AlGaN layer and the P-type contact layer on the electron blocking layer:

[0110] The reaction chamber temperature was controlled at 1050℃ and the pressure at 200 torr. Mg, N, Ga, and Al sources were introduced to complete the deposition of a P-type AlGaN layer with a thickness controlled at 100 nm and a Mg doping concentration of 5*10⁻⁶. 19 atoms / cm 3 The reaction chamber temperature was then controlled at 950℃ and the pressure at 200 torr. Mg, N, Ga, and Al sources were introduced to complete the deposition of the P-type AlGaN contact layer, with a thickness controlled to 10 nm and a Mg doping concentration of 1*10⁻⁶. 20 atoms / cm3 .

[0111] Example 2

[0112] The difference between this embodiment and Embodiment 1 is that the thickness of the two-dimensional AlGaN nucleation preparation layer is 10 nm, and the rest is the same as in Embodiment 1.

[0113] Example 3

[0114] The difference between this embodiment and Embodiment 1 is that the thickness of the two-dimensional AlGaN nucleation preparation layer is 100nm, and the rest is the same as in Embodiment 1.

[0115] Example 4

[0116] The difference between this embodiment and Embodiment 1 is that the thickness of the Al nanodot layer is 5 nm, while the rest is the same as in Embodiment 1.

[0117] Example 5

[0118] The difference between this embodiment and Embodiment 1 is that the thickness of the Al nanodot layer is 50 nm, while the rest is the same as in Embodiment 1.

[0119] Example 6

[0120] The difference between this embodiment and Embodiment 1 is that the thickness of the AlGa nanocluster nucleation point layer is 50 nm, while the rest is the same as in Embodiment 1.

[0121] Example 7

[0122] The difference between this embodiment and Embodiment 1 is that the thickness of the AlGa nanocluster nucleation point layer is 500 nm, while the rest is the same as in Embodiment 1.

[0123] Example 8

[0124] The difference between this embodiment and Embodiment 1 is that the Al component concentration in the two-dimensional AlGaN nucleation preparation layer is 0.1, and the Al component concentration in the AlGaN nucleation layer is 0.1. The rest is the same as in Embodiment 1.

[0125] Example 9

[0126] The difference between this embodiment and Embodiment 1 is that the Al component concentration in the two-dimensional AlGaN nucleation preparation layer is 0.65, and the Al component concentration in the AlGaN nucleation layer is 0.55. The rest is the same as in Embodiment 1.

[0127] Comparative Example 1

[0128] This comparative example provides a deep ultraviolet light-emitting diode epitaxial wafer, which differs from Example 1 in that the nucleation layer is only an AlGaN nucleation layer with a thickness of 1.9 μm. All other aspects are the same as in Example 1.

[0129] The deep ultraviolet light-emitting diode epitaxial wafers prepared in Examples 1-9 and Comparative Example 1 were fabricated into 15mil*15mil chips using the same chip fabrication conditions. 300 LED chips were randomly selected from each example. Tests were conducted at 120mA / 60mA currents, and the luminous efficacy improvement rate of each example relative to Comparative Example 1 was calculated. Specific test results are shown in Table 1.

[0130] Table 1 shows the performance test results of the deep ultraviolet light-emitting diode epitaxial wafers prepared in Examples 1-9.

[0131]

[0132] As can be seen from the above results, the present invention grows a nucleation layer on the buffer layer, the nucleation layer comprising a two-dimensional AlGaN nucleation preparation layer, an Al nanodot layer, an AlGa nanocluster nucleation dot layer and an AlGaN nucleation layer sequentially stacked on the buffer layer. The two-dimensional AlGaN nucleation preparation layer provides a flat nucleation surface for the growth of Al nanodot layers, reducing the contact angle of nucleation growth. The Al nanodot layer controls the density of nucleation points, which is closely related to the density of subsequent layered structures. The AlGa nanocluster nucleation layer introduces Ga atoms, enabling the Al nanodot layer to continue growing while reducing lattice mismatch with the subsequent AlGaN nucleation layer, thus improving the crystal quality of the AlGaN nucleation layer. The density of the AlGaN nucleation layer is closely related to the dislocation density of the deep ultraviolet epitaxial layer. The fusion of the AlGaN nucleation layer generates line defects, reducing the crystal quality of the GaN epitaxial layer. However, by depositing the two-dimensional AlGaN nucleation preparation layer, Al nanodot layer, and AlGa nanocluster nucleation layer, the density of the AlGaN nucleation layer can be effectively controlled to control the dislocation density, reduce the defect density, reduce the nonradiative recombination efficiency of the quantum well, and improve the luminous efficiency of the deep ultraviolet light-emitting diode.

[0133] The above description is a preferred embodiment of the invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the invention, and these improvements and modifications are also considered to be within the scope of protection of the invention.

Claims

1. A deep ultraviolet light-emitting diode epitaxial wafer, characterized in that, It includes a substrate and a buffer layer, a nucleation layer, an undoped AlGaN layer, an N-type AlGaN layer, a multiple quantum well layer, an electron blocking layer, a P-type AlGaN layer and a P-type contact layer sequentially stacked on the substrate; The nucleation layer comprises a two-dimensional AlGaN nucleation preparation layer, an Al nanodot layer, an AlGa nanocluster nucleation dot layer, and an AlGaN nucleation layer, which are sequentially stacked on the buffer layer. The thickness of the two-dimensional AlGaN nucleation preparation layer is 10nm-100nm; The thickness of the Al nanodot layer is 5nm-50nm; The thickness of the AlGa nanocluster nucleation point layer is 50nm-500nm; The thickness of the AlGaN nucleation layer is 0.5μm-5μm.

2. The deep ultraviolet light-emitting diode epitaxial wafer as described in claim 1, characterized in that, The Al component concentration in the two-dimensional AlGaN nucleation preparation layer is 0.1-1.

3. The deep ultraviolet light-emitting diode epitaxial wafer as described in claim 1, characterized in that, The Al component concentration in the AlGaN nucleation layer is 0.1-1.

4. A method for fabricating a deep ultraviolet light-emitting diode epitaxial wafer as described in any one of claims 1-3, characterized in that, Includes the following steps: Prepare the substrate; A buffer layer, a nucleation layer, an undoped AlGaN layer, an N-type AlGaN layer, a multiple quantum well layer, an electron blocking layer, a P-type AlGaN layer, and a P-type contact layer are sequentially deposited on the substrate. The nucleation layer comprises a two-dimensional AlGaN nucleation preparation layer, an Al nanodot layer, an AlGa nanocluster nucleation dot layer, and an AlGaN nucleation layer, which are sequentially stacked on the buffer layer.

5. The method for fabricating a deep ultraviolet light-emitting diode epitaxial wafer as described in claim 4, characterized in that, Depositing the two-dimensional AlGaN nucleation preparation layer on the buffer layer includes the following steps: The reaction chamber temperature was controlled at 700℃-1000℃, and the pressure was controlled at 50 torr-300 torr. N2 and NH3 were introduced as carrier gases, and N source, Ga source and Al source were introduced to complete the deposition.

6. The method for fabricating a deep ultraviolet light-emitting diode epitaxial wafer as described in claim 4, characterized in that, Depositing the Al nanodot layer on the two-dimensional AlGaN nucleation preparation layer includes the following steps: First, control the temperature of the reaction chamber at 900℃-1100℃ and the pressure at 100 torr-500 torr. Then, introduce N2 as a carrier gas and introduce an Al source to complete the deposition.

7. The method for fabricating a deep ultraviolet light-emitting diode epitaxial wafer as described in claim 4, characterized in that, Depositing the AlGa nanocluster nucleation point layer on the Al nanodot layer includes the following steps: The reaction chamber temperature was controlled at 900℃-1100℃, the pressure at 100 torr-500 torr, N2 was introduced as the carrier gas, and Al and Ga sources were introduced to complete the deposition.

8. The method for fabricating a deep ultraviolet light-emitting diode epitaxial wafer as described in claim 4, characterized in that, Depositing the AlGaN nucleation layer on the AlGa nanocluster nucleation point layer includes the following steps: The reaction chamber temperature was controlled at 1000℃-1200℃, and the pressure was controlled at 50 torr-300 torr. N2 was introduced as a carrier gas, and N2, NH3 and H2 were introduced as carrier gases. Ga source, Al source and N source were introduced to complete the deposition.

9. A deep ultraviolet light-emitting diode, characterized in that, The deep ultraviolet light-emitting diode includes a deep ultraviolet light-emitting diode epitaxial wafer as described in any one of claims 1-3.

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