P-type GaN LED epitaxial structure based on segmented annealing and compensation doping and preparation method thereof

Abstract

The invention relates to a P-type GaN LED epitaxial structure based on segmented annealing and compensation doping and a preparation method thereof, and belongs to the technical field of nitride semiconductor epitaxial growth and doping activation. The epitaxial structure sequentially comprises a buffer layer, a non-doped GaN layer, an N-type GaN layer, a multi-quantum well active layer, a P-type AlGaN electron barrier layer, a P-type GaN layer and an MgN compensation layer which are arranged on the substrate layer; wherein the MgN compensation layer is a high-concentration magnesium-doped nitride semiconductor layer, is arranged on the P-type GaN layer, and is used for compensating Mg loss and inhibiting nitrogen vacancy formation in the subsequent annealing process. The preparation method comprises the steps of performing multi-stage annealing treatment on the P-type GaN layer, performing epitaxial growth and annealing on the compensation layer, and finally performing low-temperature post-treatment annealing to form a surface passivation region. According to the structure, the Mg activation efficiency and the hole concentration are remarkably improved through an in-vivo activation and surface compensation synergistic mechanism, the contact resistance is reduced, the conductivity and the light-emitting performance of an LED device are improved, and the structure has excellent implementability and industrialization prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of light-emitting diodes, and in particular to a P-type GaN LED epitaxial structure based on segmented annealing and compensation doping and a preparation method thereof. Background Art

[0002] Nitride semiconductor light-emitting diodes (LEDs) are widely used in lighting, display, and indication due to their high efficiency, long lifespan, and environmental friendliness. As the core material for the hole injection layer in LED devices, p-type GaN's electrical conductivity has a critical impact on the overall device's luminous efficiency and energy consumption.

[0003] However, because magnesium (Mg), as a P-type dopant, has a deep acceptor energy level in GaN (approximately 200 meV) and easily forms Mg-H complexes with hydrogen (H), activation efficiency is low and hole concentration is difficult to increase. Furthermore, during traditional high-temperature annealing activation, Mg is prone to surface volatilization, accompanied by the formation of nitrogen vacancies, and the self-compensation effect further weakens conductivity. Furthermore, uneven diffusion of Mg in the crystal can lead to increased contact resistance and poor device consistency.

[0004] To overcome the above problems, researchers have proposed methods such as low-temperature annealing, dual-atmosphere heat treatment, and surface compensation doping. However, it is still difficult to strike a balance between activation efficiency and crystal quality, and it is impossible to simultaneously solve problems such as deep Mg-H dissociation and surface stability, which restricts the performance improvement of the P-type GaN layer and the further optimization of LED devices.

[0005] Therefore, there is an urgent need for an epitaxial structure and its activation method that can take into account deep doping activation, surface compensation, structural uniformity and process controllability, so as to achieve high-efficiency and high-consistency preparation of P-type GaN materials and promote the industrial development of high-performance LED devices. Summary of the Invention

[0006] The purpose of the present invention is to overcome the problems of low P-type GaN doping activation efficiency, insufficient hole concentration, high contact resistance and difficulty in balancing crystal quality in the prior art, and to provide a P-type GaN LED epitaxial structure based on segmented annealing and compensation doping and a preparation method thereof.

[0007] To achieve the above object, the present invention provides the following technical solutions: A P-type GaN LED epitaxial structure based on segmented annealing and compensation doping, comprising a buffer layer, an undoped GaN layer, an N-type GaN layer, a multi-quantum well active layer, a P-type AlGaN electron blocking layer, a P-type GaN layer, and a MgN compensation layer sequentially arranged on a substrate layer; The MgN compensation layer is a nitride material layer doped with high concentration of magnesium, which is disposed on the P-type GaN layer and is used to compensate for Mg loss and inhibit nitrogen vacancy formation during the subsequent annealing process.

[0008] The Mg doping concentration of the MgN compensation layer is 5×10 19 –1×10 20 atoms / cm 3 .

[0009] The thickness of the MgN compensation layer is 5-20 nm, and the material is magnesium-doped GaN.

[0010] The structure is subjected to low-temperature annealing treatment to form a passivation region on the surface of the MgN compensation layer. The annealing temperature is 500-600° C., the time is 3-8 minutes, and the atmosphere is N 2 .

[0011] The method for preparing the above-mentioned P-type GaN activated LED epitaxial structure comprises the following steps: (1) epitaxially growing a buffer layer, an undoped GaN layer, an N-type GaN layer, a multi-quantum well active layer, a P-type AlGaN layer, and a P-type GaN layer on a substrate in sequence; (2) The P-type GaN layer is subjected to the following annealing treatments in sequence: Initial annealing: 800–900°C, N2 or N2 / H2 atmosphere, 3–8 minutes; Medium temperature activation annealing: 900–1000°C, N2 or N2 / O2 atmosphere, 3–5 minutes; High temperature stabilization annealing: 1000–1100°C, N2 atmosphere, 5–8 minutes; (3) A MgN compensation layer is epitaxially grown on the surface of the annealed P-type GaN layer with a thickness of 5–20 nm and a Mg concentration of 5×10 19 –1×10 20 atoms / cm 3 ; (4) performing a compensation annealing treatment on the MgN compensation layer and the interface region thereunder at a temperature of 700–800° C. for 10–60 seconds in an N 2 atmosphere; (5) performing a low-temperature post-treatment annealing on the P-type GaN layer and the MgN compensation layer thereon at a temperature of 500–600° C. for 3–8 minutes in an N 2 atmosphere.

[0012] The P-type GaN layer is a single-layer structure, and its physical thickness ranges from 50 to 150 nm.

[0013] The atmosphere introduced during the initial annealing process is a mixed gas of N2 and H2, and the volume fraction of H2 is 1%-5%.

[0014] The atmosphere introduced during the medium-temperature activation annealing process is a mixed gas of N2 and O2, and the volume fraction of O2 is 1%-5%.

[0015] The present invention has the following beneficial effects: (1) Through the segmented annealing process, the P-type GaN layer is activated in multiple stages to effectively remove the Mg-H complex and increase the Mg activation rate and hole concentration; (2) The introduction of a MgN compensation layer simultaneously compensates for surface Mg loss and passivates defects during the annealing process, effectively reducing resistance and improving conductivity; (3) Final low-temperature post-annealing further optimizes the surface interface and improves the overall device luminescence efficiency and reliability; (4) The entire structural design has clear logic and a mature process path, and has excellent feasibility and industrialization prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of a P-type GaN LED epitaxial structure based on segmented annealing and compensatory doping according to the present invention. This diagram only shows the core epitaxial layer structure, without depicting additional components such as device-level electrodes and packaging. The epitaxial structure can be combined with conventional LED device preparation processes for subsequent device integration.

[0017] in: 800-substrate layer; 100-buffer layer; 200- undoped GaN layer; 300-N-type GaN layer; 400-Multi-quantum well active layer; 500-P type AlGaN electron blocking layer; 600-P-type GaN; 700-MgN compensation layer. DETAILED DESCRIPTION

[0018] The following further describes a P-type GaN LED epitaxial structure based on segmented annealing and compensatory doping and a preparation method thereof in conjunction with the accompanying drawings. The following embodiments are only used to illustrate the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0019] like Figure 1 As shown, in this embodiment, the LED epitaxial structure includes: The buffer layer 100 on the sapphire single crystal substrate layer 800 is a low-temperature AlN or GaN buffer layer; Undoped GaN layer 200; N-type GaN layer 300, doped with silicon; The multi-quantum well active layer 400 adopts an InGaN / GaN structure; P-type AlGaN electron blocking layer 500; P-type GaN layer 600, doped with Mg; MgN compensation layer 700 .

[0020] The P-type GaN layer is a Mg-doped GaN layer grown by single continuous epitaxial growth, preferably with a thickness of 50–150 nm and a doping concentration of 2×10 20 atoms / cm 3 This thickness range facilitates the formation of differentiated activation effects at different depths during the subsequent multi-stage annealing process, which not only ensures the full activation of the Mg acceptor but also helps maintain good crystallization quality and interface continuity.

[0021] After the P-type GaN layer is grown, it is subjected to the following three-stage annealing treatment in sequence: 1. Initial annealing: The temperature is selected between 800–900°C (850°C in this example) for 3–8 minutes (5 minutes in this example) in an N₂ / H₂ atmosphere with an H₂ volume fraction of 1%–5% (3% in this example). This stage is used to initially remove Mg-H complexes and repair shallow defects generated during crystal growth.

[0022] 2. Medium-temperature activation annealing: The temperature is set to 900–1000°C (950°C in this example) for 3–5 minutes (3 minutes in this example). The atmosphere is an N₂ / O₂ mixture with an O₂ volume fraction of 1%–5% (2% in this example). This stage further activates the Mg acceptors and increases the hole concentration.

[0023] 3. High-temperature stabilization annealing stage: The temperature is set to 1000–1100°C (1050°C in this example) for 5–8 minutes (6 minutes in this example) in a high-purity nitrogen atmosphere. This stage stabilizes the crystal structure, increases acceptor activation, and inhibits Mg diffusion or surface loss.

[0024] After the above annealing treatment is completed, a MgN compensation layer is epitaxially grown on the surface of the P-type GaN layer (the MgN compensation layer is a high-concentration Mg-doped GaN structure formed in a nitrogen-rich atmosphere. Its main function is to provide a compensating Mg source to the surface of the P-type GaN layer during the subsequent annealing process and suppress the formation of nitrogen vacancies through the N-rich environment, thereby improving the P-type doping uniformity and contact performance). The thickness is 5-20 nm (10 nm in this embodiment), and the Mg concentration is controlled at 5×1019 –1×10 20 atoms / cm 3 The compensation layer can not only provide an additional Mg source in the subsequent annealing, but also inhibit the formation of nitrogen vacancies, which helps to improve the carrier concentration and interface stability.

[0025] After the MgN compensation layer is formed, a compensation annealing treatment is performed at a temperature of 700-800°C (700°C in this embodiment) for 10-60 seconds (20 seconds in this embodiment) in a high-purity N2 atmosphere to activate the Mg in the MgN compensation layer and promote its diffusion downward to the surface of the P-type GaN layer to achieve surface compensation.

[0026] Finally, the P-type GaN layer and the MgN compensation layer above it are subjected to low-temperature post-treatment annealing at a temperature of 500-600°C (500°C in this embodiment) for 3-8 minutes (5 minutes in this embodiment) in a high-purity N2 atmosphere to further passivate surface defects, improve ohmic contact quality, and enhance device consistency.

[0027] In order to verify the improvement effect of the P-type GaN activation structure and the preparation method thereof on the performance of LED devices, this embodiment conducted a comparative test between the structure and a reference sample (Base).

[0028] The Base structure is an epitaxial structure without the MgN compensation layer, and the P-type GaN undergoes only a single conventional annealing step. The remaining layer structures, growth parameters, substrate type, and testing conditions are consistent with those of the present invention. Both sample groups utilize the same LED chip size, electrode structure, and packaging solution. Brightness, voltage, and luminous efficacy performance measurements were conducted at a constant drive current. The resulting comparative data are shown in Table 1.

[0029] Table 1 Performance comparison data of the present invention and comparative samples parameter Base (comparison sample) Structure of the present invention difference unit brightness 100 101.5 +1% Relative value (%) Voltage 3.510 3.490 -1% V Light Effect 28.49 29.08 +2% lm / W As shown in Table 1, after introducing the multi-stage annealing activation and MgN compensation layer structure, the luminance of the sample of the present invention increased by approximately 1%, the forward voltage decreased by approximately 1%, and the luminous efficiency increased by 2%. This result demonstrates that the synergistic mechanism of "in-body activation + surface compensation" in the P-type structure can effectively increase the activation efficiency and hole concentration of Mg acceptors, improve contact performance, and reduce device voltage loss, thereby improving the overall luminous performance and energy efficiency of the LED device.

[0030] Those skilled in the art will understand that without departing from the principles and spirit of the present invention, the temperature, atmosphere ratio, time window and structural sequence can be adjusted, which should all be included in the scope of protection of the present invention.

Claims

1. A novel P-type GaN LED epitaxial structure based on segmented annealing and compensatory doping, characterized in that: It includes a buffer layer, an undoped GaN layer, an N-type GaN layer, a multi-quantum well active layer, a P-type AlGaN electron blocking layer, a P-type GaN layer, and a MgN compensation layer, which are sequentially arranged on a substrate layer; The MgN compensation layer is a nitride material layer doped with high concentration of magnesium, which is disposed on the P-type GaN layer and is used to compensate for Mg loss and inhibit nitrogen vacancy formation during the subsequent annealing process.

2. The LED epitaxial structure according to claim 1, wherein: The magnesium doping concentration of the MgN compensation layer is 5×10 19 –1×10 20 atoms / cm -3 .

3. The LED epitaxial structure according to claim 1, wherein: The thickness of the MgN compensation layer is 5-20 nm, and the material is magnesium-doped GaN.

4. The LED epitaxial structure according to claim 1, wherein: After low-temperature annealing treatment, a passivation region is formed on the surface of the uppermost MgN compensation layer of the structure. The annealing temperature is 500-600° C., the time is 3-8 minutes, and the atmosphere is N 2 .

5. A method for preparing a P-type GaN activated LED epitaxial structure, characterized in that: The steps include: (1) epitaxially growing a buffer layer, an undoped GaN layer, an N-type GaN layer, a multi-quantum well active layer, a P-type AlGaN layer, and a P-type GaN layer on a substrate in sequence; (2) The P-type GaN layer is subjected to the following annealing treatments in sequence: Initial annealing: 800–900°C, N2 or N2 / H2 atmosphere, 3–8 minutes; Medium temperature activation annealing: 900–1000°C, N2 or N2 / O2 atmosphere, 3–5 minutes; High temperature stabilization annealing: 1000–1100°C, N2 atmosphere, 5–8 minutes; (3) A MgN compensation layer is epitaxially grown on the surface of the annealed P-type GaN layer with a thickness of 5–20 nm and a Mg concentration of 5×10 19 –1×10 20 atoms / cm -3 ; (4) performing a compensation annealing treatment on the MgN compensation layer and the interface region thereunder at a temperature of 700–800° C. for 10–60 seconds in an N 2 atmosphere; (5) Perform low-temperature post-treatment annealing on the P-type GaN layer and the MgN compensation layer above it at a temperature of 500–600°C for 3–8 minutes in an N2 atmosphere.

6. The method according to claim 5, wherein The P-type GaN layer is a single-layer structure, and its physical thickness ranges from 50 to 150 nm.

7. The method according to claim 5, characterized in that The atmosphere introduced during the initial annealing process is a mixed gas of N2 and H2, and the volume fraction of H2 is 1%-5%.

8. The method according to claim 5, characterized in that The atmosphere introduced during the medium-temperature activation annealing process is a mixed gas of N2 and O2, and the volume fraction of O2 is 1%-5%.

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