Ultraviolet light-emitting diode epitaxial wafer and its fabrication method, ultraviolet light-emitting diode

Abstract

This invention discloses an epitaxial wafer for a deep ultraviolet (UV) light-emitting diode (LED) and its fabrication method, relating to the field of semiconductor optoelectronic devices. The UV LED epitaxial wafer includes a substrate and a buffer layer, an N-type AlGaN layer, an active layer, an electron blocking layer, and a P-type AlGaN layer sequentially grown on the substrate. The active layer has a periodic structure, with each period comprising a sequentially stacked quantum well layer and a quantum barrier layer, and the number of periods in the active layer is ≥2. The quantum barrier layer comprises a sequentially stacked AlInGaN layer and a P-AlInGaN layer. Implementing this invention can effectively improve the luminous efficiency of deep ultraviolet LEDs.

Description

Technical Field

[0001] This invention relates to the field of semiconductor optoelectronic devices, and more particularly to an epitaxial wafer for an ultraviolet light-emitting diode and its fabrication method, and an ultraviolet light-emitting diode. Background Technology

[0002] Ultraviolet (UV) LEDs are mainly used in biomedicine, anti-counterfeiting, purification (water, air, etc.), computer data storage, and military applications. Compared to GaN-based blue LEDs, the development of UV LEDs faces many unique technical challenges. For example, the epitaxial growth of high-Al content AlGaN materials is difficult; generally, the higher the Al content, the lower the crystal quality, and the dislocation density is typically around 10-1. 9 -10 10 / cm 2 Even higher polarization fields exist in the quantum well and quantum barrier layers of the active region, leading to a reduction in luminescence efficiency. Furthermore, doping AlGaN materials is much more difficult than doping GaN, especially P-AlGaN, where the low activation efficiency of the dopant Mg results in insufficient holes, leading to a sharp decline in conductivity and luminescence efficiency. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide an epitaxial wafer of an ultraviolet light-emitting diode and its preparation method, which can weaken the polarization field of the trap and increase the hole concentration, thereby effectively improving the luminous efficiency.

[0004] The technical problem that this invention also needs to solve is to provide an ultraviolet light-emitting diode with high luminous efficiency.

[0005] To address the aforementioned problems, this invention discloses an epitaxial wafer for an ultraviolet light-emitting diode, comprising a substrate and a buffer layer, an N-type AlGaN layer, an active layer, an electron blocking layer, and a P-type AlGaN layer sequentially grown on the substrate; wherein, the active layer has a periodic structure, each period comprising a quantum well layer and a quantum barrier layer stacked sequentially, and the number of periods of the active layer is ≥2; the quantum barrier layer comprises an AlInGaN layer and a P-AlInGaN layer stacked sequentially.

[0006] As an improvement to the above technical solution, the proportion of Al component in the AlInGaN layer is 0.3-0.6, and the proportion of In component is 0.05-0.2.

[0007] The P-AlInGaN layer contains 0.3-0.6% Al and 0.05-0.2% In.

[0008] The P-InAlGaN layer is doped with Mg at a concentration of 1×10⁻⁶. 18 -1×1020 cm -3 .

[0009] As an improvement to the above technical solution, the quantum well layer is Al. x Ga 1-x For layer N, x ranges from 0.2 to 0.45;

[0010] The proportion of Al component in the quantum well layer is less than the proportion of Al component in the quantum barrier layer.

[0011] As an improvement to the above technical solution, in the AlInGaN layer, the Al composition gradually increases with the growth direction of the epitaxial wafer, and the proportion of Al composition at the growth starting point of each AlInGaN layer is the same as the proportion of Al composition in the quantum well layer.

[0012] In the P-AlInGaN layer, the Al content gradually decreases along the growth direction of the epitaxial wafer; and the proportion of Al content at the growth start point of each P-AlInGaN layer is the same as the proportion of Al content at the growth end point of each AlInGaN layer, and the proportion of Al content at the growth end point of each P-AlInGaN layer is the same as the proportion of Al content in the quantum well layer.

[0013] As an improvement to the above technical solution, along the epitaxial growth direction, the Al composition in the AlInGaN layer increases from 0.35 to 0.5, and the Al composition in the P-AlInGaN layer decreases from 0.5 to 0.35.

[0014] As an improvement to the above technical solution, the thickness of a single AlInGaN layer is 4-8 nm, and the thickness of a single P-AlInGaN layer is 4-8 nm.

[0015] The thickness of a single quantum well layer is 1.5-3 nm.

[0016] Accordingly, the present invention also discloses a method for preparing an ultraviolet light-emitting diode epitaxial wafer, which is used to prepare the above-mentioned ultraviolet light-emitting diode epitaxial wafer, comprising:

[0017] A substrate is provided on which a buffer layer, an N-type AlGaN layer, an active layer, an electron blocking layer, and a P-type AlGaN layer are sequentially grown. The active layer has a periodic structure, and each period includes a quantum well layer and a quantum barrier layer stacked sequentially. The number of periods of the active layer is ≥2. The quantum barrier layer includes an AlInGaN layer and a P-AlInGaN layer stacked sequentially.

[0018] As an improvement to the above technical solution, the growth temperature of the AlInGaN layer is 1020-1100℃, and the growth pressure is 50-100mbar.

[0019] The growth temperature of the P-AlInGaN layer is 1020-1100℃, and the growth pressure is 50-100mbar.

[0020] As an improvement to the above technical solution, the buffer layer is an AlN layer, which is grown by MOCVD at a growth temperature of 1200-1300℃ and a growth pressure of 30-50mbar.

[0021] During growth, TMAl is introduced into the MOCVD process as an Al source, and NH3 is introduced in a pulsed manner as an N source.

[0022] Accordingly, the present invention also discloses an ultraviolet light-emitting diode, which includes the ultraviolet light-emitting diode epitaxial wafer described above.

[0023] Implementing this invention has the following beneficial effects:

[0024] 1. In the epitaxial wafer of the ultraviolet light-emitting diode of the present invention, the quantum barrier layer comprises sequentially stacked AlInGaN layers and P-AlInGaN layers. By introducing In into the quantum barrier layer, its crystal quality can be improved, making the quantum well-quantum barrier interface clearer, reducing defects, and thus weakening the polarization effect between the well and the barrier, thereby improving the luminous efficiency. Simultaneously, by introducing the P-AlInGaN layer into the quantum barrier layer, the hole concentration in the active layer can be increased, improving the internal quantum efficiency, and thus improving the luminous efficiency. Furthermore, this doping can also reduce the series resistance and lower the operating voltage of the light-emitting diode.

[0025] 2. In the epitaxial wafer of the ultraviolet light-emitting diode of the present invention, the Al composition in the AlInGaN layer gradually increases along the growth direction of the epitaxial wafer, while the Al composition in the P-AlInGaN layer gradually decreases along the growth direction of the epitaxial wafer; and the Al composition at the start point of the AlInGaN layer and the end point of the P-AlInGaN layer is the same as the Al composition of the quantum well layer. Based on this structure, the strong polarization field generated by the different band gaps of the quantum well layer and the quantum barrier layer can be weakened, thereby improving the recombination efficiency of electrons and holes and improving the luminous efficiency.

[0026] 3. In the ultraviolet light-emitting diode epitaxial wafer of the present invention, an AlN layer grown at high temperature (>1200℃) is used as a buffer layer. This AlN layer has a good crystal structure, which can effectively reduce the lattice mismatch between the substrate and the AlGaN epitaxial layer, reduce the dislocation density, prevent dislocations from extending to the active layer, reduce the non-radiative recombination centers generated by dislocations in the quantum well, and improve the luminous efficiency of the quantum well. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of an epitaxial wafer of an ultraviolet light-emitting diode in one embodiment of the present invention;

[0028] Figure 2 This is a schematic diagram of the quantum barrier layer in one embodiment of the present invention;

[0029] Figure 3 This is a flowchart of a method for preparing an epitaxial wafer of an ultraviolet light-emitting diode in one embodiment of the present invention. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in further detail below.

[0031] refer to Figure 1 and Figure 2 This invention discloses an epitaxial wafer for an ultraviolet light-emitting diode, comprising a substrate 1 and a buffer layer 2, an N-type AlGaN layer 3, an active layer 4, an electron blocking layer 5, and a P-type AlGaN layer 6 sequentially deposited on the substrate 1. The active layer 4 has a periodic structure with a period number ≥ 2, and each period includes a quantum well layer 41 and a quantum barrier layer 42. The quantum well layer 41 is made of Al... x Ga 1-x In layer N, x is 0.2-0.45 (i.e., the proportion of Al component is 0.2-0.45). The proportion of Al component in quantum well layer 41 is less than that in quantum barrier layer 42.

[0032] The quantum barrier layer 42 comprises sequentially stacked AlInGaN layers 421 and P-AlInGaN layers 422. By introducing In throughout the quantum barrier layer 42, the crystal quality of the quantum barrier layer 42 is improved, resulting in a clearer quantum well-quantum barrier interface, fewer defects, and thus reduced polarization effects between the well and barrier, improving luminous efficiency. Simultaneously, by introducing the P-AlInGaN layer 422 into the quantum barrier layer 42, the hole concentration in the active layer 4 is increased, improving the internal quantum efficiency and further enhancing luminous efficiency. Furthermore, this doping also reduces the series resistance and lowers the operating voltage of the light-emitting diode.

[0033] The Al component in the AlInGaN layer 421 comprises 0.3-0.6%, with examples of 0.33, 0.36, 0.39, 0.42, 0.45, 0.48, 0.51, 0.54, or 0.57, but is not limited thereto. The In component in the AlInGaN layer 421 comprises 0.05-0.2%, with examples of 0.07, 0.09, 0.11, 0.13, 0.15, 0.17, or 0.19. The thickness of the AlInGaN layer 421 is 4-8 nm, with examples of 4.2 nm, 4.5 nm, 5 nm, 5.5 nm, 6 nm, 6.5 nm, 7 nm, or 7.5 nm, but is not limited thereto.

[0034] The P-AlInGaN layer 422 contains 0.3-0.6% Al, with examples of 0.33, 0.36, 0.39, 0.42, 0.45, 0.48, 0.51, 0.54, or 0.57%, but is not limited to these values. The P-AlInGaN layer 422 contains 0.05-0.2% In, with examples of 0.07, 0.09, 0.11, 0.13, 0.15, 0.17, or 0.19%. The P-AlInGaN layer 422 has a thickness of 4-8 nm, with examples of 4.3 nm, 4.5 nm, 5 nm, 5.5 nm, 6 nm, 6.5 nm, 7 nm, or 7.5 nm%, but is not limited to these values. The P-AlInGaN layer 422 is doped with Mg, but is not limited to this. The doping concentration of the P-AlInGaN layer 422 is 1×10⁻⁶. 18 -1×10 20 cm -3 .

[0035] Specifically, the Al composition in AlInGaN layer 421 and P-AlInGaN layer 422 remains constant or exhibits a changing trend. Preferably, in one embodiment of the present invention, the Al composition in AlInGaN layer 421 gradually increases along the growth direction of the epitaxial wafer. In P-AlInGaN layer 422, the Al composition gradually decreases along the growth direction of the epitaxial wafer. Based on this changing trend, the strong polarization electric field generated by the different band gaps of the quantum well-quantum barrier can be weakened, thereby improving the recombination efficiency of electrons and holes. More preferably, in AlInGaN layer 421, the Al composition gradually increases along the growth direction of the epitaxial wafer, and the proportion of Al composition at the growth starting point of each AlInGaN layer 421 is the same as the proportion of Al composition in quantum well layer 41. In the P-AlInGaN layer 422, the Al content gradually decreases along the growth direction of the epitaxial wafer. The proportion of Al content at the growth start point of each P-AlInGaN layer 422 is the same as the proportion of Al content at the growth end point of the AlInGaN layer 421, and the proportion of Al content at the growth end point of each P-AlInGaN layer 422 is the same as the proportion of Al content in the quantum well layer 41. For example, the Al content in the AlInGaN layer 421 increases from 0.35 to 0.5, the Al content in the P-AlInGaN layer 422 decreases from 0.5 to 0.35, and the proportion of Al content in the quantum well layer 41 is 0.35. Based on this configuration, the polarization field can be further weakened, improving luminescence efficiency.

[0036] The active layer 4 has 3-8 periods, and the thickness of a single quantum well layer 41 is 1.5-3 nm, exemplarily 1.5 nm, 2 nm, 2.5 nm or 3 nm, but not limited to these.

[0037] The substrate 1 can be a sapphire substrate, a silicon substrate, or a silicon carbide substrate, but is not limited to these. A sapphire substrate is preferred.

[0038] The buffer layer 2 is an AlN layer or an AlGaN layer, but is not limited to these. Preferably, the buffer layer 2 is an AlN layer, and it is a high-temperature AlN layer, i.e., its growth temperature is >1200℃. This type of AlN layer has a good crystal structure, which can effectively reduce the lattice mismatch between the substrate and the AlGaN epitaxial layer, reduce the dislocation density, prevent dislocations from extending to the active layer, reduce the non-radiative recombination centers generated by dislocations in the quantum well, and improve the luminous efficiency of the quantum well. The thickness of the buffer layer 2 is 1-4μm, exemplary of which are 1.4μm, 1.8μm, 2.2μm, 2.6μm, 3μm, 3.4μm, or 3.8μm, but is not limited to these.

[0039] In this layer, the N-type AlGaN layer 3 provides electrons, which then recombine with holes in the active layer 4 to emit light. Specifically, the Al content in the N-type AlGaN layer 3 is 0.4-0.6%, with exemplary values ​​of 0.43, 0.45, 0.48, 0.51, 0.55, or 0.58, but not limited to these. The doping element in the N-type AlGaN layer 3 is Si, but not limited to this. The Si doping concentration in the N-type AlGaN layer 3 is 5 × 10⁻⁶. 18 -1×10 20 cm -3 An example is 6.5 × 10 18 cm -3 8×10 18 cm -3 1.5×10 19 cm -3 3×10 19 cm -3 5.5×10 19 cm -3 Or 9×10 19 cm -3 However, it is not limited to this. Specifically, the thickness of the N-type AlGaN layer 3 is 1-3 μm, with exemplary thicknesses of 1.4 μm, 1.8 μm, 2.2 μm, 2.6 μm or 3 μm, but it is not limited to this.

[0040] Among them, electron blocking layer 5 is Al y Ga 1-y N layers, where y is 0.6-0.7, meaning the Al content in electron blocking layer 5 is 0.6-0.7%. The Al content in electron blocking layer 5 is higher than that in active layer 4, which effectively limits electron overflow and reduces hole blocking, thus improving the hole-to-quantum-well injection efficiency. The thickness of electron blocking layer 5 is 10-40 nm.

[0041] The doping element in layer 6 of the p-type AlGaN is Mg, but it is not limited to this. The Mg doping concentration is 5 × 10⁶. 19 -5×10 20 cm -3 The Al content in the P-type AlGaN layer 6 is 0.25-0.5%, and the thickness of the P-type AlGaN layer 6 is 200-500 nm.

[0042] Accordingly, refer to Figure 3 The present invention also discloses a method for preparing an ultraviolet light-emitting diode epitaxial wafer, which is used to prepare the above-mentioned ultraviolet light-emitting diode epitaxial wafer, and includes the following steps:

[0043] S1: Provides a substrate;

[0044] S2: A buffer layer, an N-type AlGaN layer, an active layer, an electron blocking layer, a P-type AlGaN layer, and a P-type contact layer are sequentially grown on the substrate.

[0045] Specifically, S2 includes:

[0046] S21: Grow a buffer layer on the substrate;

[0047] Specifically, an AlN layer can be grown via PVD as a buffer layer, or an AlGaN layer can be grown via MOCVD as a buffer layer. Preferably, in one embodiment of the invention, the AlN layer is grown via MOCVD at a growth temperature of 1200-1300°C and a growth pressure of 30-50 mbar. During growth, TMAl is introduced into the MOCVD chamber as an Al source, and NH3 is pulsedly introduced as an N source. By pulsedly introducing NH3, the crystal quality of AlN can be further improved.

[0048] S22: An N-type AlGaN layer on an undoped AlGaN layer;

[0049] Among them, the N-type AlGaN layer was grown by MOCVD at a growth temperature of 1000-1300℃ and a growth pressure of 50-100mbar.

[0050] S23: Growth of multiple quantum well layers on N-type AlGaN layers;

[0051] Multiple quantum well layers and quantum barrier layers are periodically grown using MOCVD to obtain a multi-quantum well layer. The growth temperature of both the quantum well layer and the quantum barrier layer is 1020-1100℃, and the growth pressure is 50-100mbar.

[0052] S24: Growth of an electron blocking layer on a multi-quantum-well layer;

[0053] The electron blocking layer is grown using MOCVD at a temperature of 1000-1100℃ and a growth pressure of 50-100mbar.

[0054] S25: A P-type AlGaN layer is grown on an electron blocking layer;

[0055] Among them, P-type AlGaN layers were grown using MOCVD at a growth temperature of 1000-1100℃ and a growth pressure of 50-100mbar.

[0056] The present invention will be further described below with reference to specific embodiments:

[0057] Example 1

[0058] This embodiment provides an epitaxial wafer for an ultraviolet light-emitting diode, as shown in the reference. Figure 1 , Figure 2 It includes a substrate 1 and a buffer layer 2, an N-type AlGaN layer 3, an active layer 4, an electron blocking layer 5, and a P-type AlGaN layer 6 sequentially grown on the substrate 1.

[0059] In this design, substrate 1 is a sapphire substrate, buffer layer 2 is an AlN layer with a thickness of 1.5 μm, and the N-type AlGaN layer 3 is doped with Si at a doping concentration of 1 × 10⁻⁶. 19 cm -3 The Al component accounts for 0.5%, and its thickness is 2μm.

[0060] The multiple quantum well layers have a periodic structure with 5 periods. Each period includes a quantum well layer 51 and a quantum barrier layer 52. The quantum well layer 51 is made of Al. x Ga 1-x The N-layer (x = 0.35) has a thickness of 2 nm. The quantum barrier layer 52 consists of sequentially stacked AlInGaN layers 521 and P-AlInGaN layers 522. The Al composition of AlInGaN layer 521 is 0.4 (maintained constant), and the In composition is 0.1, with a thickness of 6 nm. The Al composition of P-AlInGaN layer 522 is 0.5 (maintained constant), and the In composition is 0.1, with a thickness of 6 nm. The dopant element of P-AlInGaN layer 522 is Mg, with a doping concentration of 1 × 10⁻⁶. 19 cm -3 .

[0061] Among them, electron blocking layer 5 is Al y Ga 1-y The N-layer (y = 0.65) has a thickness of 25 nm. The p-type AlGaN layer 6 has a thickness of 200 nm and a Mg doping concentration of 5 × 10⁻⁶. 19 cm -3 The Al content in the p-type AlGaN layer 6 is 0.3%.

[0062] The method for fabricating the epitaxial wafer of the ultraviolet light-emitting diode in this embodiment is as follows:

[0063] (1) Provide a substrate;

[0064] (2) An AlN layer is grown on the substrate;

[0065] Specifically, AlN layers were grown in MOCVD at a temperature of 1250℃ and a pressure of 40 mbar. During growth, TMAl was introduced into the MOCVD system as the Al source, and NH3 was introduced in a pulsed manner as the N source.

[0066] (3) An N-type AlGaN layer on an undoped AlGaN layer;

[0067] Specifically, the N-type AlGaN layer was grown using MOCVD at a growth temperature of 1150℃ and a growth pressure of 75mbar.

[0068] (4) Growth of multiple quantum well layers on N-type AlGaN layers;

[0069] Multiple quantum well layers and quantum barrier layers are periodically grown using MOCVD to obtain a multi-quantum well layer. The growth temperature for both the quantum well and quantum barrier layers is 1080℃, and the growth pressure is 90 mbar.

[0070] (5) Grow an electron blocking layer on a multi-quantum-well layer;

[0071] Specifically, the electron blocking layer was grown using MOCVD at a temperature of 1080℃ and a growth pressure of 90 mbar.

[0072] (6) Grow a P-type AlGaN layer on an electron blocking layer;

[0073] Specifically, P-type AlGaN layers were grown using MOCVD at a growth temperature of 1050℃ and a growth pressure of 95 mbar.

[0074] Example 2

[0075] This embodiment provides an epitaxial wafer for an ultraviolet light-emitting diode, as shown in the reference. Figure 1 , Figure 2 It includes a substrate 1 and a buffer layer 2, an N-type AlGaN layer 3, an active layer 4, an electron blocking layer 5, and a P-type AlGaN layer 6 sequentially grown on the substrate 1.

[0076] In this design, substrate 1 is a sapphire substrate, buffer layer 2 is an AlN layer with a thickness of 1.5 μm, and the N-type AlGaN layer 3 is doped with Si at a doping concentration of 1 × 10⁻⁶. 19 cm -3The Al component accounts for 0.5%, and its thickness is 2μm.

[0077] The multiple quantum well layers have a periodic structure with 5 periods. Each period includes a quantum well layer 51 and a quantum barrier layer 52. The quantum well layer 51 is made of Al. x Ga 1-x The N-layer (x = 0.35) has a thickness of 2 nm. The quantum barrier layer 52 comprises sequentially stacked AlInGaN layers 521 and P-AlInGaN layers 522. In AlInGaN layer 521, the Al content gradually increases from 0.35 to 0.5, and the In content is 0.1, with a thickness of 6 nm. In P-AlInGaN layer 522, the Al content gradually increases from 0.35 to 0.5, and the In content is 0.1, with a thickness of 6 nm. The dopant element in P-AlInGaN layer 522 is Mg, with a doping concentration of 1 × 10⁻⁶. 19 cm -3 .

[0078] Among them, electron blocking layer 5 is Al y Ga 1-y The N-layer (y = 0.65) has a thickness of 25 nm. The p-type AlGaN layer 6 has a thickness of 200 nm and a Mg doping concentration of 5 × 10⁻⁶. 19 cm -3 The Al content in the p-type AlGaN layer 6 is 0.3%.

[0079] The method for fabricating the epitaxial wafer of the ultraviolet light-emitting diode in this embodiment is as follows:

[0080] (1) Provide a substrate;

[0081] (2) An AlN layer is grown on the substrate;

[0082] Specifically, AlN layers were grown in MOCVD at a temperature of 1250℃ and a pressure of 40 mbar. During growth, TMAl was introduced into the MOCVD system as the Al source, and NH3 was introduced in a pulsed manner as the N source.

[0083] (3) An N-type AlGaN layer on an undoped AlGaN layer;

[0084] Specifically, the N-type AlGaN layer was grown using MOCVD at a growth temperature of 1150℃ and a growth pressure of 75mbar.

[0085] (4) Growth of multiple quantum well layers on N-type AlGaN layers;

[0086] Multiple quantum well layers and quantum barrier layers are periodically grown using MOCVD to obtain a multi-quantum well layer. The growth temperature for both the quantum well and quantum barrier layers is 1080℃, and the growth pressure is 90 mbar.

[0087] (5) Grow an electron blocking layer on a multi-quantum-well layer;

[0088] Specifically, the electron blocking layer was grown using MOCVD at a temperature of 1080℃ and a growth pressure of 90 mbar.

[0089] (6) Grow a P-type AlGaN layer on an electron blocking layer;

[0090] Specifically, P-type AlGaN layers were grown using MOCVD at a growth temperature of 1050℃ and a growth pressure of 95 mbar.

[0091] Example 3

[0092] This embodiment provides an epitaxial wafer for an ultraviolet light-emitting diode, as shown in the reference. Figure 1 , Figure 2 It includes a substrate 1 and a buffer layer 2, an N-type AlGaN layer 3, an active layer 4, an electron blocking layer 5, and a P-type AlGaN layer 6 sequentially grown on the substrate 1.

[0093] In this design, substrate 1 is a sapphire substrate, buffer layer 2 is an AlN layer with a thickness of 1.5 μm, and the N-type AlGaN layer 3 is doped with Si at a doping concentration of 1 × 10⁻⁶. 19 cm -3 The Al component accounts for 0.5%, and its thickness is 2μm.

[0094] The multiple quantum well layers have a periodic structure with 5 periods. Each period includes a quantum well layer 51 and a quantum barrier layer 52. The quantum well layer 51 is made of Al. x Ga 1-x The N-layer (x = 0.35) has a thickness of 2 nm. The quantum barrier layer 52 comprises sequentially stacked AlInGaN layers 521 and P-AlInGaN layers 522. In AlInGaN layer 521, the Al content gradually increases from 0.35 to 0.5, the In content is 0.1, and its thickness is 6 nm. In P-AlInGaN layer 522, the Al content gradually decreases from 0.5 to 0.35, the In content is 0.1, and its thickness is 6 nm. The dopant element in P-AlInGaN layer 522 is Mg, with a doping concentration of 1 × 10⁻⁶. 19 cm -3 .

[0095] Among them, electron blocking layer 5 is Al y Ga 1-y The N-layer (y = 0.65) has a thickness of 25 nm. The p-type AlGaN layer 6 has a thickness of 200 nm and a Mg doping concentration of 5 × 10⁻⁶. 19 cm -3The Al content in the p-type AlGaN layer 6 is 0.3%.

[0096] The method for fabricating the epitaxial wafer of the ultraviolet light-emitting diode in this embodiment is as follows:

[0097] (1) Provide a substrate;

[0098] (2) An AlN layer is grown on the substrate;

[0099] Specifically, AlN layers were grown in MOCVD at a temperature of 1250℃ and a pressure of 40 mbar. During growth, TMAl was introduced into the MOCVD system as the Al source, and NH3 was introduced in a pulsed manner as the N source.

[0100] (3) An N-type AlGaN layer on an undoped AlGaN layer;

[0101] Specifically, the N-type AlGaN layer was grown using MOCVD at a growth temperature of 1150℃ and a growth pressure of 75mbar.

[0102] (4) Growth of multiple quantum well layers on N-type AlGaN layers;

[0103] Multiple quantum well layers and quantum barrier layers are periodically grown using MOCVD to obtain a multi-quantum well layer. The growth temperature for both the quantum well and quantum barrier layers is 1080℃, and the growth pressure is 90 mbar.

[0104] (5) Grow an electron blocking layer on a multi-quantum-well layer;

[0105] Specifically, the electron blocking layer was grown using MOCVD at a temperature of 1080℃ and a growth pressure of 90 mbar.

[0106] (6) Grow a P-type AlGaN layer on an electron blocking layer;

[0107] Specifically, P-type AlGaN layers were grown using MOCVD at a growth temperature of 1050℃ and a growth pressure of 95 mbar.

[0108] Comparative Example 1

[0109] This embodiment provides an epitaxial wafer for an ultraviolet light-emitting diode, as shown in the reference. Figure 1 It includes a substrate 1 and a buffer layer 2, an N-type AlGaN layer 3, an active layer 4, an electron blocking layer 5, and a P-type AlGaN layer 6 sequentially grown on the substrate 1.

[0110] In this design, substrate 1 is a sapphire substrate, buffer layer 2 is an AlN layer with a thickness of 1.5 μm, and the N-type AlGaN layer 3 is doped with Si at a doping concentration of 1 × 10⁻⁶. 19 cm -3The Al component accounts for 0.5%, and its thickness is 2μm.

[0111] The multiple quantum well layers have a periodic structure with 5 periods. Each period includes a quantum well layer 51 and a quantum barrier layer 52. The quantum well layer 51 is made of Al. x Ga 1-x Layer N (x = 0.35) has a thickness of 2 nm. The quantum barrier layer 52 is Al. z Ga 1-y The N-layer (x = 0.5) has a thickness of 12 nm.

[0112] The method for fabricating the epitaxial wafer of the ultraviolet light-emitting diode in this comparative example is as follows:

[0113] (1) Provide a substrate;

[0114] (2) An AlN layer is grown on the substrate;

[0115] Specifically, AlN layers were grown in MOCVD at a temperature of 1250℃ and a pressure of 40 mbar. During growth, TMAl was introduced into the MOCVD system as the Al source, and NH3 was introduced in a pulsed manner as the N source.

[0116] (3) An N-type AlGaN layer on an undoped AlGaN layer;

[0117] Specifically, the N-type AlGaN layer was grown using MOCVD at a growth temperature of 1150℃ and a growth pressure of 75mbar.

[0118] (4) Growth of multiple quantum well layers on N-type AlGaN layers;

[0119] Multiple quantum well layers and quantum barrier layers are periodically grown using MOCVD to obtain a multi-quantum well layer. The growth temperature for both the quantum well and quantum barrier layers is 1080℃, and the growth pressure is 90 mbar.

[0120] (5) Grow an electron blocking layer on a multi-quantum-well layer;

[0121] Specifically, the electron blocking layer was grown using MOCVD at a temperature of 1080℃ and a growth pressure of 90 mbar.

[0122] (6) Grow a P-type AlGaN layer on an electron blocking layer;

[0123] Specifically, P-type AlGaN layers were grown using MOCVD at a growth temperature of 1050℃ and a growth pressure of 95 mbar.

[0124] Comparative Example 2

[0125] This embodiment provides an epitaxial wafer for an ultraviolet light-emitting diode, as shown in the reference. Figure 1 It includes a substrate 1 and a buffer layer 2, an N-type AlGaN layer 3, an active layer 4, an electron blocking layer 5, and a P-type AlGaN layer 6 sequentially grown on the substrate 1.

[0126] In this design, substrate 1 is a sapphire substrate, buffer layer 2 is an AlN layer with a thickness of 1.5 μm, and the N-type AlGaN layer 3 is doped with Si at a doping concentration of 1 × 10⁻⁶. 19 cm -3 The Al component accounts for 0.5%, and its thickness is 2μm.

[0127] The multiple quantum well layers have a periodic structure with 5 periods. Each period includes a quantum well layer 51 and a quantum barrier layer 52. The quantum well layer 51 is made of Al. x Ga 1-x The N layer (x = 0.35) has a thickness of 2 nm. The quantum barrier layer 52 is an AlInGaN layer with an Al composition of 0.4 (maintained constant) and an In composition of 0.1, and a thickness of 12 nm.

[0128] Among them, electron blocking layer 5 is Al y Ga 1-y The N-layer (y = 0.65) has a thickness of 25 nm. The p-type AlGaN layer 6 has a thickness of 200 nm and a Mg doping concentration of 5 × 10⁻⁶. 19 cm -3 The Al content in the p-type AlGaN layer 6 is 0.3%.

[0129] The method for fabricating the epitaxial wafer of the ultraviolet light-emitting diode in this comparative example is as follows:

[0130] (1) Provide a substrate;

[0131] (2) An AlN layer is grown on the substrate;

[0132] Specifically, AlN layers were grown in MOCVD at a temperature of 1250℃ and a pressure of 40 mbar. During growth, TMAl was introduced into the MOCVD system as the Al source, and NH3 was introduced in a pulsed manner as the N source.

[0133] (3) An N-type AlGaN layer on an undoped AlGaN layer;

[0134] Specifically, the N-type AlGaN layer was grown using MOCVD at a growth temperature of 1150℃ and a growth pressure of 75mbar.

[0135] (4) Growth of multiple quantum well layers on N-type AlGaN layers;

[0136] Multiple quantum well layers and quantum barrier layers are periodically grown using MOCVD to obtain a multi-quantum well layer. The growth temperature for both the quantum well and quantum barrier layers is 1080℃, and the growth pressure is 90 mbar.

[0137] (5) Grow an electron blocking layer on a multi-quantum-well layer;

[0138] Specifically, the electron blocking layer was grown using MOCVD at a temperature of 1080℃ and a growth pressure of 90 mbar.

[0139] (6) Grow a P-type AlGaN layer on an electron blocking layer;

[0140] Specifically, P-type AlGaN layers were grown using MOCVD at a growth temperature of 1050℃ and a growth pressure of 95 mbar.

[0141] Comparative Example 3

[0142] This embodiment provides an epitaxial wafer for an ultraviolet light-emitting diode, as shown in the reference. Figure 1 , Figure 2 It includes a substrate 1 and a buffer layer 2, an N-type AlGaN layer 3, an active layer 4, an electron blocking layer 5, and a P-type AlGaN layer 6 sequentially grown on the substrate 1.

[0143] In this design, substrate 1 is a sapphire substrate, buffer layer 2 is an AlN layer with a thickness of 1.5 μm, and the N-type AlGaN layer 3 is doped with Si at a doping concentration of 1 × 10⁻⁶. 19 cm -3 The Al component accounts for 0.5%, and its thickness is 2μm.

[0144] The multiple quantum well layers have a periodic structure with 5 periods. Each period includes a quantum well layer 51 and a quantum barrier layer 52. The quantum well layer 51 is made of Al. x Ga 1-x The N-layer (x = 0.35) has a thickness of 2 nm. The quantum barrier layer 52 is a P-AlInGaN layer. Its doping element is Mg, with a doping concentration of 1 × 10⁻⁶. 19 cm -3 cm -3 Its Al component content is 0.5 (maintained constant), its In component content is 0.1, and its thickness is 12nm.

[0145] Among them, electron blocking layer 5 is Al y Ga 1-y The N-layer (y = 0.65) has a thickness of 25 nm. The p-type AlGaN layer 6 has a thickness of 200 nm and a Mg doping concentration of 5 × 10⁻⁶. 19 cm -3 The Al content in the p-type AlGaN layer 6 is 0.3%.

[0146] The method for fabricating the epitaxial wafer of the ultraviolet light-emitting diode in this comparative example is as follows:

[0147] (1) Provide a substrate;

[0148] (2) An AlN layer is grown on the substrate;

[0149] Specifically, AlN layers were grown in MOCVD at a temperature of 1250℃ and a pressure of 40 mbar. During growth, TMAl was introduced into the MOCVD system as the Al source, and NH3 was introduced in a pulsed manner as the N source.

[0150] (3) An N-type AlGaN layer on an undoped AlGaN layer;

[0151] Specifically, the N-type AlGaN layer was grown using MOCVD at a growth temperature of 1150℃ and a growth pressure of 75mbar.

[0152] (4) Growth of multiple quantum well layers on N-type AlGaN layers;

[0153] Multiple quantum well layers and quantum barrier layers are periodically grown using MOCVD to obtain a multi-quantum well layer. The growth temperature for both the quantum well and quantum barrier layers is 1080℃, and the growth pressure is 90 mbar.

[0154] (5) Grow an electron blocking layer on a multi-quantum-well layer;

[0155] Specifically, the electron blocking layer was grown using MOCVD at a temperature of 1080℃ and a growth pressure of 90 mbar.

[0156] (6) Grow a P-type AlGaN layer on an electron blocking layer;

[0157] Specifically, P-type AlGaN layers were grown using MOCVD at a growth temperature of 1050℃ and a growth pressure of 95 mbar.

[0158] The ultraviolet light-emitting diode epitaxial wafers obtained in Examples 1-3 and Comparative Examples 1-3 were tested using the following specific testing methods:

[0159] (1) Test its brightness;

[0160] (2) Each epitaxial wafer is fabricated into a light-emitting diode with a positive structure, and online testing and sorting are performed to calculate its yield.

[0161] The specific results are as follows:

[0162] Brightness (mW) Forward voltage (VF / V) Yield (%) Example 1 6.1 6.18 98.1 Example 2 6.3 6.19 98.3 Example 3 6.8 6.15 98.8 Comparative Example 1 5.6 6.2 97.5 Comparative Example 2 5.7 6.2 97.6 Comparative Example 3 5.6 6.2 97.8

[0163] As can be seen from the table, when the quantum barrier layer of the present invention is introduced into the epitaxial structure, the luminescence efficiency is effectively improved, the forward voltage is reduced, and the yield is improved.

[0164] 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. An epitaxial wafer for an ultraviolet light-emitting diode, characterized in that, The device includes a substrate and a buffer layer, an N-type AlGaN layer, an active layer, an electron blocking layer, and a P-type AlGaN layer sequentially grown on the substrate; wherein the active layer has a periodic structure, each period including a quantum well layer and a quantum barrier layer stacked sequentially, and the number of periods of the active layer is ≥2; the quantum well layer is Al x Ga 1-x For layer N, x ranges from 0.2 to 0.45; The quantum barrier layer comprises sequentially stacked AlInGaN layers and P-AlInGaN layers; the proportion of In component in the AlInGaN layer is 0.05-0.2%; the proportion of In component in the P-AlInGaN layer is 0.05-0.2%. The P-AlInGaN layer is doped with Mg at a concentration of 1×10⁻⁶. 18 -1×10 20 cm -3 ; Along the growth direction of the epitaxial wafer, the Al composition in the AlInGaN layer increases from 0.35 to 0.5, and the Al composition in the P-AlInGaN layer decreases from 0.5 to 0.

35. The proportion of Al component in the quantum well layer is less than the proportion of Al component in the quantum barrier layer; The substrate is a sapphire substrate, and the buffer layer is an AlN layer, which is grown by MOCVD at a growth temperature of 1200-1300℃ and a growth pressure of 30-50mbar. During growth, TMAl is introduced into the MOCVD process as an Al source, and NH3 is introduced in a pulsed manner as an N source.

2. The ultraviolet light-emitting diode epitaxial wafer as described in claim 1, characterized in that, The proportion of Al component at the growth start point of each AlInGaN layer is the same as the proportion of Al component in the quantum well layer; The proportion of Al component at the growth start point of each P-AlInGaN layer is the same as the proportion of Al component at the growth end point of each AlInGaN layer, and the proportion of Al component at the growth end point of each P-AlInGaN layer is the same as the proportion of Al component in the quantum well layer.

3. The ultraviolet light-emitting diode epitaxial wafer as described in claim 1, characterized in that, The thickness of a single AlInGaN layer is 4-8 nm, and the thickness of a single P-AlInGaN layer is 4-8 nm; The thickness of a single quantum well layer is 1.5-3 nm.

4. A method for preparing an ultraviolet light-emitting diode epitaxial wafer, used to prepare the ultraviolet light-emitting diode epitaxial wafer as described in any one of claims 1-3, characterized in that, include: A substrate is provided on which a buffer layer, an N-type AlGaN layer, an active layer, an electron blocking layer, and a P-type AlGaN layer are sequentially grown. The active layer has a periodic structure, and each period includes a quantum well layer and a quantum barrier layer stacked sequentially. The number of periods of the active layer is ≥2. The quantum barrier layer includes an AlInGaN layer and a P-AlInGaN layer stacked sequentially.

5. The preparation method according to claim 4, characterized in that, The growth temperature of the AlInGaN layer is 1020-1100℃, and the growth pressure is 50-100mbar. The growth temperature of the P-AlInGaN layer is 1020-1100℃, and the growth pressure is 50-100mbar.

6. An ultraviolet light-emitting diode, characterized in that, Including the ultraviolet light-emitting diode epitaxial wafer as described in any one of claims 1-3.

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