Ultraviolet light emitting diode epitaxial wafer and preparation method and application thereof

Abstract

The application relates to an ultraviolet light emitting diode epitaxial wafer and a preparation method and application thereof. The epitaxial wafer comprises a substrate, a buffer layer, a P-type layer, an electron blocking layer, a multi-quantum well light emitting layer and an N-type layer which are sequentially arranged on the substrate. The buffer layer is located between the substrate and the P-type layer, the buffer layer is an undoped AlN buffer layer or an undoped AlGaN buffer layer, the P-type layer is a P-type doped GaN layer or a P-type doped AlGaN layer, and the N-type layer is an N-type doped AlGaN layer. The epitaxial wafer of the application does not need to pass through a flip GaN / AlGaN-LED chip processing technology or use a complex technology such as a bonding substrate and a stripping substrate to form a vertical and flip GaN / AlGaN-LED chip when a chip of the UV-LED is processed subsequently. Only a relatively simple normal GaN / AlGaN-LED processing technology is needed to manufacture a high-quality UV-LED chip, and the assembly process is greatly facilitated.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor technology, specifically relating to an epitaxial wafer of an ultraviolet light-emitting diode, its preparation method, and its application. Background Technology

[0002] Ultraviolet light-emitting diodes (UV-LEDs) are light-emitting diodes that emit near-ultraviolet light. Currently, most UV-LEDs are fabricated using materials such as aluminum oxide (Al2O3), aluminum nitride (AlN), silicon (Si), AlN substrates deposited on aluminum oxide, or silicon carbide (SiC). The NP-type LED structure is formed by chemical vapor deposition (MOCVD) on substrates, involving the sequential epitaxy of N-type doped epitaxial materials and their associated structural materials, the light-emitting layer and its associated structural materials, and P-type doped epitaxial materials and their associated structural materials. The traditional structure of a UV-LED epitaxial wafer includes a substrate and sequentially stacked layers on the substrate surface: an aluminum nitride (AlN) or high-aluminum-content aluminum gallium nitride (AlGaN) buffer layer, a high-aluminum-content n-type aluminum gallium nitride (AlGaN) layer, a multiple quantum well (MQW) light-emitting layer, an electron blocking layer (EBL) layer, and a low-aluminum-content P-type aluminum gallium nitride (AlGaN) layer. In use, UV-LED chips are formed through flip-chip LED processing technology or vertical-flip-chip LED processing technology.

[0003] However, traditional UV-LEDs have some problems in production, mainly including the following two aspects:

[0004] (1) Epitaxial growth of AlN or AlGaN buffer layers with high aluminum content by MOCVD equipment requires particularly high epitaxial temperature, typically 1400℃ or even higher. However, the maximum temperature of mainstream GaN-based MOCVD equipment cannot meet this epitaxial temperature requirement. If high-temperature MOCVD equipment is to be used, it often needs to be specially made, which greatly increases the production cost of epitaxial wafers.

[0005] (2) It is extremely difficult to perform high-quality P-type doping on AlGaN epitaxial materials with high aluminum content. Therefore, the traditional structure of UV-LED epitaxial wafers can only use low-aluminum-content P-type doped AlGaN or P-type GaN material layers as P-type layers. The band gap of such low-aluminum-content P-type AlGaN or P-type GaN layers is often lower than that of the MQW light-emitting layer. That is, the UV light emitted by the MQW will be absorbed by this material layer, which will seriously affect the light extraction. Therefore, the traditional UV-LED epitaxial wafers can only guide the light to be extracted from the N-type high-aluminum-content AlGaN and AlN materials of the UV-LED through flip-chip or vertical flip-chip processing technology. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide an improved ultraviolet light emitting diode epitaxial wafer and its preparation method.

[0007] The present invention also provides an application of ultraviolet light emitting diode epitaxial wafers in UV-LEDs.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] An epitaxial wafer for an ultraviolet light-emitting diode includes a substrate and a buffer layer disposed on the substrate. The buffer layer is an undoped AlN buffer layer or an undoped AlGaN buffer layer. The epitaxial wafer further includes a P-type layer, an electron blocking layer, a multiple quantum well light-emitting layer, and an N-type layer sequentially disposed on the buffer layer. The buffer layer is located between the substrate and the P-type layer. The P-type layer is a P-type doped GaN layer or a P-type doped AlGaN layer, and the N-type layer is an N-type doped AlGaN layer.

[0010] According to some embodiments of the present invention, the P-type layer is a P-type doped AlGaN layer or a GaN layer, the electron blocking layer is an AlGaN electron blocking layer, and the multi-quantum-well emitting layer is an AlGaN multi-quantum-well emitting layer.

[0011] According to some embodiments of the present invention, the electron blocking layer is a doped or undoped AlGaN electron blocking layer, the multi-quantum-well emitting layer is a doped AlGaN multi-quantum-well emitting layer, the Al content in the N-type layer is greater than the Al content in the multi-quantum-well emitting layer, and the Al content in the buffer layer is greater than the Al content in the multi-quantum-well emitting layer.

[0012] According to some embodiments of the present invention, the thickness of the buffer layer is greater than or equal to 0.01 μm. Preferably, the thickness of the buffer layer is 0.01 to 10 μm, more preferably 0.01 μm to 2 μm.

[0013] According to some embodiments of the present invention, the thickness of the P-type layer is 0.01~20μm, preferably 0.01~1μm.

[0014] According to some embodiments of the present invention, the thickness of the N-type layer is 0.1~20μm, preferably 0.5~2μm.

[0015] Another technical solution adopted by the present invention is: a method for preparing the above-mentioned ultraviolet light-emitting diode epitaxial wafer, the preparation method comprising the following steps:

[0016] (1) Grow a buffer layer on the substrate;

[0017] (2) A P-type layer is grown on the buffer layer;

[0018] (3) An electron blocking layer is grown on the P-type layer;

[0019] (4) A multi-quantum-well light-emitting layer is grown on the electron blocking layer;

[0020] (5) An N-type layer is grown on the multi-quantum-well light-emitting layer.

[0021] According to some embodiments of the present invention, in step (1), the buffer layer is an undoped AlN buffer layer or an undoped Al... x Ga 1-x For an N-type buffer layer, 0.3 ≤ x < 1, when the buffer layer is an undoped AlN buffer layer, it is grown by PVD deposition or MOCVD under growth conditions of 20 mbar to 500 mbar pressure and 1000℃ to 1400℃; when the buffer layer is an undoped Al... x Ga 1-x For the N buffer layer, when 0.3 ≤ x < 1, its growth conditions are a pressure of 20 mbar to 500 mbar and a temperature of 1000℃ to 1400℃.

[0022] In step (1), when the buffer layer is an undoped AlN buffer layer, it can be prepared using a PVD device or an MOCVD device.

[0023] According to some embodiments of the present invention, the growth conditions in step (2) are a pressure of 20 mbar to 500 mbar and a temperature of 850°C to 1400°C.

[0024] According to some embodiments of the present invention, in step (4), the Al component content in the multi-quantum-well light-emitting layer is less than the Al component content in the buffer layer.

[0025] According to some embodiments of the present invention, the growth conditions in step (5) are 1000°C to 1400°C, and the Al component content of the N-type layer is greater than the Al component content in the quantum well light-emitting layer.

[0026] Another technical solution adopted by the present invention is: an ultraviolet light-emitting diode, which includes the ultraviolet light-emitting diode epitaxial wafer described above.

[0027] Due to the application of the above-mentioned technical solution, the present invention has the following advantages compared with the prior art:

[0028] The epitaxial wafer of the present invention, with a P-type layer on the bottom and an N-type layer on top, allows for the fabrication of UV-LED chips without the need for flip-chip GaN / AlGaN-LED chip fabrication processes or complex processes such as substrate bonding and substrate stripping to form vertical and flip-chip GaN / AlGaN-LED chips. High-quality UV-LED chips can be produced using a relatively simple upright GaN / AlGaN-LED fabrication process, greatly simplifying the assembly process. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of the ultraviolet light-emitting diode epitaxial wafer in Example 1;

[0030] In the figure: 1. Substrate; 2. Buffer layer; 3. P-type layer; 4. Electron blocking layer; 5. Multi-quantum well light-emitting layer; 6. N-type layer. Detailed Implementation

[0031] Without further detailed explanation, it is believed that those skilled in the art can utilize the present invention to the fullest extent based on the foregoing description. Therefore, the embodiments provided below are merely illustrative of the present invention and are not intended to limit the scope of the invention in any way.

[0032] Example 1

[0033] The ultraviolet light-emitting diode epitaxial wafer provided in this embodiment is epitaxially grown using a metal-organic chemical vapor deposition (MOCVD) device and is prepared by the following method:

[0034] (1) Using sapphire as substrate 1;

[0035] (2) An undoped Al layer with a thickness of 200 nm was grown on the substrate surface at a pressure of 50 mbar and a temperature of 1350 °C. x Ga 1-x N buffer layers, 0.3 ≤ x < 1;

[0036] (3) Under the conditions of 100 mbar and 1150 °C, a 50 nm thick P-type doped AlGaN layer was grown on the buffer layer, with Mg as the dopant and the dopant concentration being 1 × 10⁻⁶. 20 cm- 3 ;

[0037] (4) An undoped AlGaN electron blocking layer with a thickness of 20 nm was grown on a P-type doped AlGaN layer at a pressure of 50 mbar and a temperature of 1350 °C.

[0038] (5) Under a pressure of 50 mbar and a temperature of 1350 °C, an AlGaN multi-quantum well light-emitting layer with a thickness of 3 nm is grown on the AlGaN electron blocking layer, and the Al component content in the AlGaN multi-quantum well light-emitting layer is lower than the Al component content in the buffer layer.

[0039] (6) An N-type doped AlGaN layer with a thickness of 1 μm was grown on the AlGaN multi-quantum-well light-emitting layer at 50 mbar and 1350 °C, using Si as the dopant and the dopant concentration being 1 × 10⁻⁶. 19 cm- 3 This results in the Al content in the N-type doped AlGaN layer being higher than the Al content in the multi-quantum-well light-emitting layer.

[0040] The epitaxial wafer prepared by the above method has the following structure. Figure 1 As shown, it includes a substrate 1, a buffer layer 2, a P-type layer 3, an electron blocking layer 4, a multi-quantum-well light-emitting layer 5, and an N-type layer 6, which are stacked sequentially.

[0041] When the epitaxial wafer of the ultraviolet light-emitting diode in this example is used on the ultraviolet light-emitting diode in a positive mounting manner, the ultraviolet light-emitting diode emits light normally.

[0042] In this example, the epitaxial wafer is constructed by sequentially stacking a buffer layer 2, a P-type layer 3, an electron blocking layer 4, a multi-quantum well light-emitting layer 5, and an N-type layer 6 on a substrate 1. Since the P-type layer 3 is grown first, followed by the N-type layer, the P-type layer 3 is at the bottom and the N-type layer 6 is at the top. In subsequent processing and assembly, there is no need to use flip-chip or vertical-flip-chip processes; only upright assembly is required, making assembly convenient and simple.

[0043] In other embodiments, a P-type doped GaN layer can also be grown on the buffer layer 2 as a P-type layer.

[0044] Example 2

[0045] The ultraviolet light-emitting diode epitaxial wafer provided in this embodiment is prepared by using both PVD equipment and metal-organic chemical vapor deposition (MOCVD) equipment, and is prepared by the following method:

[0046] (1) PVD depositing an AlN buffer layer on sapphire;

[0047] (2) A 50 nm thick P-type doped GaN layer was grown on the buffer layer at 100 mbar and 1150 °C, using Mg as the dopant with a concentration of 1 × 10⁻⁶. 20 cm- 3 ;

[0048] (3) An undoped AlGaN electron blocking layer with a thickness of 20 nm was grown on a P-type doped GaN layer at a pressure of 50 mbar and a temperature of 1350 °C.

[0049] (4) Under a pressure of 50 mbar and a temperature of 1350 °C, an AlGaN multi-quantum well light-emitting layer with a thickness of 3 nm is grown on the AlGaN electron blocking layer, and the Al component content in the AlGaN multi-quantum well light-emitting layer is lower than the Al component content in the buffer layer.

[0050] (5) An N-type doped AlGaN layer with a thickness of 1 μm was grown on the AlGaN multi-quantum-well light-emitting layer at 50 mbar and 1350 °C, using Si as the dopant and the dopant concentration being 1 × 10⁻⁶. 19 cm- 3 This results in the Al content in the N-type doped AlGaN layer being higher than the Al content in the multi-quantum-well light-emitting layer.

[0051] When the epitaxial wafer of the ultraviolet light-emitting diode in this example is used on the ultraviolet light-emitting diode in a positive mounting manner, the ultraviolet light-emitting diode emits light normally.

[0052] In other embodiments, an AlGaN layer may be grown on the AlN layer, followed by the growth of a P-type layer.

[0053] In this example, the epitaxial wafer is grown by depositing an AlN layer as a buffer layer on substrate 1 using a PVD device, and then growing a P-type layer, which avoids the need to grow a pure AlN layer at high temperature.

[0054] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. An epitaxial wafer for an ultraviolet light-emitting diode, comprising a substrate and a buffer layer disposed on the substrate, characterized in that: The buffer layer is an undoped AlN buffer layer or an undoped Al... x Ga 1-x The N-type buffer layer has a capacity of 0.3 ≤ x < 1. The epitaxial wafer further includes a P-type layer, an electron blocking layer, a multiple quantum well light-emitting layer, and an N-type layer sequentially disposed on the buffer layer. The buffer layer is located between the substrate and the P-type layer, and the P-type layer is a P-type doped AlGaN layer. The N-type layer is an N-type doped AlGaN layer, using silicon as the dopant; The electron blocking layer is an undoped AlGaN electron blocking layer; The multi-quantum-well light-emitting layer is an AlGaN multi-quantum-well light-emitting layer or a doped AlGaN multi-quantum-well light-emitting layer; The Al content in the AlGaN multi-quantum-well light-emitting layer is lower than that in the buffer layer; The Al content in the N-type doped AlGaN layer is higher than that in the multi-quantum-well light-emitting layer; The method for fabricating the epitaxial wafer of the ultraviolet light-emitting diode includes the following steps: (1) Grow a buffer layer on the substrate; (2) A P-type layer is grown on the buffer layer; (3) An electron blocking layer is grown on the P-type layer; (4) A multi-quantum-well light-emitting layer is grown on the electron blocking layer; (5) An N-type layer is grown on the multi-quantum-well light-emitting layer; In step (1), when the buffer layer is an undoped AlN buffer layer, it is grown by PVD deposition or MOCVD under growth conditions of pressure 20mbar~500mbar and temperature 1000℃~1400℃; when the buffer layer is an undoped Al... x Ga 1-x For the N buffer layer, when 0.3 ≤ x < 1, its growth conditions are pressure 20 mbar ~ 500 mbar and temperature 1000℃ ~ 1400℃. The growth conditions in step (2) are a pressure of 20 mbar to 500 mbar and a temperature of 850℃ to 1400℃; the growth conditions in step (5) are 1000℃ to 1400℃.

2. The ultraviolet light-emitting diode epitaxial wafer according to claim 1, characterized in that: The thickness of the buffer layer is greater than or equal to 0.01 μm.

3. The ultraviolet light-emitting diode epitaxial wafer according to claim 1, characterized in that: The thickness of the P-type layer is 0.01~20μm.

4. The ultraviolet light-emitting diode epitaxial wafer according to claim 1, characterized in that: The thickness of the N-type layer is 0.1~20μm.

5. A method for preparing an ultraviolet light-emitting diode epitaxial wafer according to any one of claims 1 to 4, characterized in that, The preparation method includes the following steps: (1) Grow a buffer layer on the substrate; (2) A P-type layer is grown on the buffer layer; (3) An electron blocking layer is grown on the P-type layer; (4) A multi-quantum-well light-emitting layer is grown on the electron blocking layer; (5) An N-type layer is grown on the multi-quantum-well light-emitting layer.

6. An ultraviolet light-emitting diode, comprising the ultraviolet light-emitting diode epitaxial wafer as described in any one of claims 1 to 4.

Images