An ε-Ga2O3-based PIN structure heterojunction solar-blind ultraviolet detector and its preparation method

Abstract

The present invention discloses an ε-Ga2O3-based PIN structure heterojunction solar-blind ultraviolet detector and a preparation method thereof. The detector is made of new materials, and this solution is proposed to address the problems of high power consumption in the prior art. It includes a top electrode, a NiO film, an ε-Ga2O3 intrinsic layer, a 4H-SiC substrate and a bottom electrode stacked in sequence. The preparation steps include: pretreatment of the 4H-SiC substrate; metal organic chemical vapor deposition of the ε-Ga2O3 intrinsic layer; radio frequency magnetron sputtering of the NiO film; and electron beam evaporation to prepare the top electrode and the bottom electrode. The advantage is that the amount of Ga2O3 used is reduced, which can reduce power consumption. ε-Ga2O3 is grown on the 4H-SiC substrate. Based on the excellent thermal conductivity of SiC of 4.9W / cm·K, a large amount of heat in the ε-Ga2O3 intrinsic layer can be transferred from the 4H-SiC substrate. At the same time, the in-plane lattice constant difference between the orthorhombic structure ε-Ga2O3 crystal and 4H-SiC is small, which can improve the crystallization quality of the ε-Ga2O3 intrinsic layer, thereby improving the detection performance of the photodetector.

Description

Technical Field

[0001] The present invention relates to a detector made of new materials, and in particular to an ε-Ga2O3-based PIN structure heterojunction solar-blind ultraviolet detector and a preparation method thereof. Background Art

[0002] The band gap width of Ga2O3 material is 4.4-5.3eV, and the wavelength range corresponding to its absorption band edge is 250-280Nm, which can cover most of the solar-blind ultraviolet region without the need for additional energy band modulation. It is one of the most ideal materials for preparing solar-blind photodetectors.

[0003] To operate in extreme environments such as high temperature and high pressure, solar-blind photodetectors require excellent heat dissipation capabilities. However, due to the inherently low thermal conductivity of the ε-Ga2O3 material (0.1-0.3 W / cm·K), heat dissipation is precisely the greatest challenge for ε-Ga2O3 photodetectors. Consequently, in practical applications, Ga2O3 solar-blind photodetectors operating at high temperatures suffer from high energy consumption, low light-to-dark ratios, and poor stability.

[0004] CN115642197A discloses a Ga2O3-based PIN heterojunction solar-blind UV detector and its fabrication method. This method, in its one-sided pursuit of lower dark current and higher signal-to-noise ratio, excessively thickens the light-absorbing layer, using Ga2O3 for both the N-type layer and the intrinsic layer. This results in severe heat generation and extremely high power consumption. Furthermore, doubling the amount of Ga2O3 used, combined with process and material costs, increases the overall fabrication cost by approximately fourfold, making it unsuitable for large-scale commercial use. Summary of the Invention

[0005] The present invention aims to provide an ε-Ga2O3-based PIN structure heterojunction solar-blind ultraviolet detector and a preparation method thereof, so as to solve the problems existing in the above-mentioned prior art.

[0006] The ε-Ga2O3-based PIN structure heterojunction solar-blind ultraviolet detector described in the present invention includes a top electrode, a NiO film, an ε-Ga2O3 intrinsic layer, a 4H-SiC substrate and a bottom electrode stacked in sequence from top to bottom; wherein the NiO film serves as a P-type layer, the ε-Ga2O3 intrinsic layer serves as a light absorption layer, and the 4H-SiC substrate serves as an N-type layer, thereby forming a PIN structure heterojunction.

[0007] The NiO film has a truncated cone structure, and the top electrode has a circular ring structure; the outer edge of the top electrode is aligned with the outer edge of the NiO film in a vertical position.

[0008] The NiO film extends out of a supporting portion on one side; and the top electrode extends out of a soldering gold portion above the supporting portion.

[0009] The method for preparing an ε-Ga2O3-based PIN structure heterojunction solar-blind ultraviolet detector described in the present invention comprises the following steps:

[0010] S1. Pretreatment of 4H-SiC substrate;

[0011] S2. Preparation of an ε-Ga2O3 intrinsic layer on one side of a 4H-SiC substrate using metal organic chemical vapor deposition;

[0012] S3. Preparation of NiO thin film on the ε-Ga2O3 intrinsic layer using RF magnetron sputtering;

[0013] S4 uses electron beam evaporation to prepare the top electrode on the NiO film and the bottom electrode on the other side of the 4H-SiC substrate.

[0014] In step S1, the selected 4H-SiC substrate has a microtube density of ≤0.5cm -2 , the resistivity range is 0.015~0.025Ω*cm, and the chip direction is Offaxis: 4.0°toward±0.5°; first soak in H2O2 / H2O / HCl=1:6:1 solution, then move to H2O2 / H2O / NH3·H2O=1:5:1 for soaking, and finally transfer to HF (5%) solution for soaking to remove surface contaminants; finally rinse with deionized water five times and dry.

[0015] In step S2, MOCVD two-step growth is adopted, triethylgallium is selected as gallium source, deionized water is used as oxygen source, and argon is used as carrier gas;

[0016] First growth step: growing the nucleation layer at 560°C with a constant VI / III ratio of 69 for 30 min;

[0017] The second growth step: epitaxial layer at 640 ° C, the growth time is 120 minutes.

[0018] The sputtering power was set to 130 W, the pressure in the chamber was 5 mT, the oxygen-argon ratio was 1:1, the deposition rate was 0.5 Nm / min, and the sputtering time was 30 min.

[0019] The hole concentration of the NiO film is about 5.1×10 19 cm -3 , the hole mobility is about 0.1 cm 2 / (Vs).

[0020] In step S4, the electron beam voltage is controlled to be ≥9.7KeV, and the power setting ratio is controlled to be 15% to 20%; the deposition rate of Ti is The deposition rate of Au is The electrodes were alloyed by rapid thermal annealing in a nitrogen atmosphere at a temperature of 470°C for 1 min. A bottom electrode was prepared under the 4H-SiC substrate.

[0021] In step S4, the electron beam voltage is controlled to be ≥9.7KeV, and the power setting ratio is controlled to be 15% to 20%; the deposition rate of Ni is The deposition rate of Au is A top electrode is prepared on top of the NiO film.

[0022] The ε-Ga2O3-based PIN structure heterojunction solar-blind UV detector and its preparation method described in this invention have the advantages of reducing Ga2O3 usage and power consumption. ε-Ga2O3 is grown on a 4H-SiC substrate. Due to SiC's excellent thermal conductivity of 4.9 W / cm·K, a large amount of heat from the ε-Ga2O3 intrinsic layer is transferred from the 4H-SiC substrate. Furthermore, the orthorhombic structure of the ε-Ga2O3 crystals has a small difference in in-plane lattice constant with that of the 4H-SiC, which improves the crystallization quality of the ε-Ga2O3 intrinsic layer and, consequently, the detection performance of the photodetector. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a structural schematic diagram of the solar-blind ultraviolet detector described in the present invention.

[0024] Figure 2 It is a transmittance curve diagram of the P-NiO thin film in the present invention.

[0025] Figure 3 This is an X-ray diffraction scan of the ε-Ga2O3 intrinsic layer described in the present invention.

[0026] Figure 4 It is a graph of IV characteristic curves of the solar-blind ultraviolet detector described in the present invention under different light intensities.

[0027] Figure 5 The graph is a photoresponse IV curve of the solar-blind ultraviolet detector of the present invention at different temperatures, in dark state and under 254 Nm illumination.

[0028] Figure 6 It is the normalized IT characteristic curve of the solar-blind ultraviolet detector described in the present invention at 0V bias and different temperatures.

[0029] Figure 7 is the solar-blind ultraviolet detector of the present invention at different temperatures d Summary chart.

[0030] Reference numerals:

[0031] 10-top electrode, 11-weld metal part;

[0032] 20-NiO film, 21-supporting portion;

[0033] 30-ε-Ga2O3 intrinsic layer;

[0034] 40-4H-SiC substrate;

[0035] 50-Bottom electrode. DETAILED DESCRIPTION

[0036] like Figure 1 As shown, the ε-Ga2O3-based PIN structure heterojunction solar-blind ultraviolet detector described in the present invention includes a top electrode 10, a NiO film 20, an ε-Ga2O3 intrinsic layer 30, a 4H-SiC substrate 40 and a bottom electrode 50 stacked in sequence from top to bottom; wherein the NiO film 20 serves as a P-type layer, the ε-Ga2O3 intrinsic layer 30 serves as a light absorption layer, and the 4H-SiC substrate 40 serves as an N-type layer, thereby forming a PIN structure heterojunction.

[0037] The NiO film 20 has a truncated cone structure, and the top electrode 10 has a circular ring structure; the outer edge of the top electrode 10 is vertically aligned with the outer edge of the NiO film 20 .

[0038] A supporting portion 21 is extended from one side of the NiO thin film 20 ; a soldering portion 11 is extended from the top electrode 10 above the supporting portion 21 .

[0039] The method for preparing an ε-Ga2O3-based PIN structure heterojunction solar-blind ultraviolet detector described in the present invention comprises the following steps:

[0040] S1. Pretreatment of the 4H-SiC substrate 40;

[0041] S2 using metal organic chemical vapor deposition method to prepare ε-Ga2O3 intrinsic layer 30 on one side of the 4H-SiC substrate 40;

[0042] S3. A NiO film 20 is prepared on the ε-Ga2O3 intrinsic layer 30 using RF magnetron sputtering;

[0043] In S4 , a top electrode 10 is formed on the NiO film 20 by using an electron beam evaporation process, and a bottom electrode 50 is formed on the other side of the 4H—SiC substrate 40 .

[0044] In step S1, the selected 4H-SiC substrate 40 has a micropipe density of ≤0.5 cm -2, the resistivity range is 0.015~0.025Ω*cm, and the chip direction is Offaxis: 4.0°toward±0.5°; first soak in H2O2 / H2O / HCl=1:6:1 solution, then move to H2O2 / H2O / NH3·H2O=1:5:1 for soaking, and finally transfer to HF (5%) solution for soaking to remove surface contaminants; finally rinse with deionized water five times and dry.

[0045] In step S2, MOCVD two-step growth is adopted, triethylgallium is selected as gallium source, deionized water is used as oxygen source, and argon is used as carrier gas;

[0046] First growth step: growing the nucleation layer at 560°C with a constant VI / III ratio of 69 for 30 min;

[0047] The second growth step: epitaxial layer at 640 ° C, the growth time is 120 minutes.

[0048] The sputtering power was set to 130 W, the pressure in the chamber was 5 mT, the oxygen-argon ratio was 1:1, the deposition rate was 0.5 Nm / min, and the sputtering time was 30 min.

[0049] The hole concentration of the NiO film 20 is about 5.1×10 19 cm -3 , the hole mobility is about 0.1 cm 2 / (Vs).

[0050] In step S4, the electron beam voltage is controlled to be ≥9.7KeV, and the power setting ratio is controlled to be 15% to 20%; the deposition rate of Ti is The deposition rate of Au is The electrodes were alloyed by rapid thermal annealing in a nitrogen atmosphere at a temperature of 470° C. for 1 minute. A bottom electrode 50 was prepared under the 4H-SiC substrate 40 .

[0051] In step S4, the electron beam voltage is controlled to be ≥9.7KeV, and the power setting ratio is controlled to be 15% to 20%; the deposition rate of Ni is The deposition rate of Au is A top electrode 10 is formed on the NiO film 20 .

[0052] Experimental test analysis:

[0053] like Figure 2As shown, the absorption edge of the NiO film 20 is between 310 nm and 340 nm, while maintaining a transmittance of approximately 50% in the wavelength range of daylight-blind light. Its frustum-shaped design minimizes light loss before reaching the absorption layer, while also functioning as a P-type layer. Even if part of the ε-Ga2O3 intrinsic layer 30 is covered by the NiO film 20, sufficient light signals can be obtained at a transmittance close to 50%. The circular ring design of the top electrode 10 minimizes light obstruction and effectively derives electrical signals. Providing a solder joint 11 provides good wiring conditions.

[0054] The X-ray diffraction (XRD) 2θ-ω scanning results of the ε-Ga2O3 intrinsic layer 30 grown on the 4H-SiC substrate 40 show that Figure 3 As shown, the diffraction peaks at 38.90° and 59.80° correspond to the (004) and (006) planes of ε-Ga2O3, respectively. The highest intensity diffraction peak corresponds to the (004) plane of 4H-SiC, with no other diffraction peaks observed. This indicates that the Ga2O3 film grown on 4H-SiC substrate 40 is pure ε-phase.

[0055] The results of testing the device under different light intensities of 254Nm are as follows Figure 4 As shown, the optical power density range is 0.76mW / cm 2 ~2.92mW / cm 2 , the voltage test range is -10V~3V. Obviously, under different light intensities, the device always shows typical rectification characteristics in the entire voltage test range. Under 0V bias, the dark current of the device is 5.81×10 -11 ampere, at an optical power density of 2.92mW / cm 2 Under the sunlight-blind light, the photocurrent is 2.11×10 -8 A, the light-to-dark current ratio reaches 1.6×10 2 .

[0056] Figure 5 The photocurrent and dark current of the solar-blind UV detector under 0V conditions change with increasing temperature. It can be seen that the device can still maintain a high photocurrent and a small dark current as the temperature rises. Even when working at 200℃, the light-to-dark current ratio of the device can be close to 10 3 .

[0057] Figure 6 The time response characteristics of solar-blind UV detectors at different operating temperatures at 0V are demonstrated. Figure 7 is the time constant τ of the device at different temperatures d Summary. It can be seen that as the operating temperature increases, the device still maintains a stable time response characteristic. Calculate the τ when the device is working at 200℃d =117ms, compared with τ at room temperature d =88ms, the degradation degree is relatively low.

[0058] Those skilled in the art can make various other corresponding changes and deformations based on the technical solutions and concepts described above, and all of these changes and deformations should fall within the scope of protection of the claims of the present invention.

Claims

1. An ε-Ga2O3-based PIN structure heterojunction solar-blind ultraviolet detector, characterized in that: The invention comprises a top electrode (10), a NiO film (20), an ε-Ga2O3 intrinsic layer (30), a 4H-SiC substrate (40) and a bottom electrode (50) which are stacked in sequence from top to bottom; wherein the NiO film (20) serves as a P-type layer, the ε-Ga2O3 intrinsic layer (30) serves as a light absorption layer, and the 4H-SiC substrate (40) serves as an N-type layer, thereby forming a PIN structure heterojunction; The NiO film (20) has a truncated cone structure, and the top electrode (10) has a circular ring structure; the outer edge of the top electrode (10) is aligned with the outer edge of the NiO film (20) in a vertical position; The NiO film (20) extends a supporting portion (21) on one side; and the top electrode (10) extends a soldering portion (11) above the supporting portion (21).

2. The method for preparing the ε-Ga2O3-based PIN structure heterojunction solar-blind ultraviolet detector according to claim 1, characterized in that: The following steps are involved: S1. Pre-treating the 4H-SiC substrate (40); S2. Preparing an ε-Ga2O3 intrinsic layer (30) on one side of a 4H-SiC substrate (40) using a metal organic chemical vapor deposition method; S3. Preparing a NiO film (20) on the ε-Ga2O3 intrinsic layer (30) using RF magnetron sputtering; S4 uses an electron beam evaporation process to prepare a top electrode (10) on the NiO film (20), and prepares a bottom electrode (50) on the other side of the 4H-SiC substrate (40).

3. The preparation method according to claim 2, characterized in that: In step S1, the selected 4H-SiC substrate (40) has a microtube density of ≤0.5 cm -2 , the resistivity range is 0.015~0.025Ω*cm, and the chip direction is Offaxis: 4.0°toward±0.5°; first soak in H2O2 / H2O / HCl=1:6:1 solution, then move to H2O2 / H2O / NH3·H2O=1:5:1 for soaking, and finally transfer to HF (5%) solution for soaking to remove surface contaminants; finally rinse with deionized water five times and dry.

4. The preparation method according to claim 2, characterized in that In step S2, MOCVD two-step growth is adopted, triethylgallium is selected as gallium source, deionized water is used as oxygen source, and argon is used as carrier gas; First growth step: growing the nucleation layer at 560°C with a constant VI / III ratio of 69 for 30 min; The second growth step: epitaxial layer at 640 ° C, the growth time is 120 minutes.

5. The preparation method according to claim 2, characterized in that: In step S3 , the sputtering power is set to 130 W, the pressure in the chamber is 5 mT, the oxygen-argon ratio is 1:1, the deposition rate is 0.5 Nm / min, and the sputtering time is 30 minutes.

6. The preparation method according to claim 5, characterized in that: The hole concentration of the NiO film (20) is 5.1×10 19 cm -3 , the hole mobility is 0.1 cm 2 / (Vs).

7. The preparation method according to claim 2, characterized in that: In step S4, the electron beam voltage is controlled to be ≥9.7KeV, and the power setting ratio is controlled to be 15% to 20%; the deposition rate of Ti is The deposition rate of Au is The electrode is alloyed by rapid thermal annealing in a nitrogen atmosphere, with an annealing temperature of 470° C. and an annealing time of 1 minute; and a bottom electrode (50) is prepared below the 4H-SiC substrate (40).

8. The preparation method according to claim 2, characterized in that: In step S4, the electron beam voltage is controlled to be ≥9.7KeV, and the power setting ratio is controlled to be 15% to 20%; the deposition rate of Ni is The deposition rate of Au is A top electrode (10) is prepared on the NiO film (20).

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