A molybdenum rhenium sulfide / gan heterojunction ultraviolet photodiode and a preparation method thereof
By introducing Mo doping into the ReS2/GaN heterojunction, a Re1-xMoxS2/GaN heterojunction ultraviolet photodiode was prepared, which solved the problems of high turn-on voltage and reverse leakage current of existing 2D TMDC photodiode devices, and achieved low power consumption and high responsivity photodetection effect, which is suitable for visible light communication and photocatalysis.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SOUTH CHINA UNIV OF TECH
- Filing Date
- 2026-04-03
- Publication Date
- 2026-07-10
AI Technical Summary
Existing 2D TMDC-based photodiode devices suffer from excessively large Fermi level differences, resulting in high turn-on voltage and large reverse leakage current. This makes it difficult to achieve low power consumption and high response speed in the near-ultraviolet band, thus failing to meet the requirements of high-speed optical communication and ultraviolet imaging.
By introducing Mo doping into two-dimensional ReS2 to form n-type doping, the Fermi level difference is reduced and defect levels are introduced to prepare Re1-xMoxS2/GaN heterojunction ultraviolet photodiodes. Low turn-on voltage, low reverse leakage current and high responsivity are achieved by using low-voltage CVD, low-temperature PLD combined with high-temperature MOCVD and wet transfer processes.
This invention achieves low turn-on voltage, low reverse leakage current, and high responsivity in the near-ultraviolet region, providing a possible solution to the performance bottleneck of two-dimensional material optoelectronic devices. It is controllable, safe, and has low raw material costs.
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Figure CN122373483A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of semiconductor technology, specifically relating to a Re 1-x Mo x S2 / GaN heterojunction ultraviolet photodiode and its fabrication. Background Technology
[0002] With the rapid development of the optoelectronic field, high-sensitivity, wide-bandwidth, and low-power photodetectors have become a research hotspot. Two-dimensional materials, with their atomic-level thickness, flexible band structure control capabilities, and excellent photoelectric response characteristics, are gradually becoming a research focus in optoelectronic devices. Among numerous two-dimensional materials, transition metal chalcogenides (2D TMDCs) are considered important candidate materials for constructing high-speed optical communication devices and ultraviolet light detection elements due to their direct bandgap characteristics and excellent carrier dynamics.
[0003] However, current 2D TMDC-based photodiodes still face numerous limitations. Most of these devices rely on heterojunction interfaces formed by van der Waals forces, lacking robust chemical bonding. This results in limited efficiency in carrier separation and transport, leading to severe recombination of photogenerated carriers and reduced conductivity. Furthermore, these devices generally lack ideal diode rectification characteristics, exhibiting high turn-on voltage and large reverse leakage current. This makes it difficult to achieve low-power and high-response photodetection in the near-ultraviolet band (360-370 nm), thus failing to meet the demands of practical applications such as high-speed optical communication and ultraviolet imaging. Summary of the Invention
[0004] To address the challenges of achieving low turn-on voltage, low reverse leakage current, and high conductivity in the near-ultraviolet band in traditional 2D TMDC / GaN optoelectronic devices due to the large Fermi level difference hindering electronic transitions, this invention proposes a molybdenum sulfide rhenium (Re) 1-x Mo x This invention relates to a ReS2 / GaN heterojunction ultraviolet photodiode and its fabrication method. The invention utilizes controllable Mo doping to form n-type doping in two-dimensional ReS2, introducing defect energy levels to achieve low-power and high-response photodetection. On one hand, an excessive Fermi level difference between ReS2 and GaN increases the device's turn-on voltage and reverse leakage current. Forming n-type doping reduces the Fermi level difference, decreasing the potential of the built-in electric field, thereby reducing the diode's turn-on voltage and reverse leakage current, and lowering device power consumption. On the other hand, sulfur vacancies generated during doping can introduce defect energy levels into the band gap, creating defect recombination centers that serve as transition levels between the valence and conduction bands, reducing the energy required for electron transitions and further improving conductivity, thus achieving high-speed device response.
[0005] The Re of the present invention 1-x Mox The S2 / GaN heterojunction photodetector exhibits low turn-on voltage, low reverse leakage current, high responsivity, and fast response time in the near-ultraviolet region. Furthermore, the method of this invention offers high controllability and safety, and the raw materials involved are relatively inexpensive and readily available.
[0006] The objective of this invention is achieved through the following technical solution:
[0007] A molybdenum sulfide rhenium / GaN heterojunction ultraviolet photodiode includes a GaN substrate, an Al2O3 buffer layer disposed on the GaN substrate, and Re on the Al2O3 buffer layer. x Mo 1-x S2 layer; the Al2O3 buffer layer partially covers the GaN substrate, Re x Mo 1-x The S2 layer covers the upper surface of the Al2O3 buffer layer; electrodes are located on the upper portion of the GaN substrate not covered by the Al2O3 buffer layer, Re x Mo 1-x Electrodes are provided on the upper part of the S2 layer.
[0008] Re x Mo 1-x In layer S2, x is 0.03~0.08, preferably 0.04~0.065, more preferably 0.04~0.06, and even more preferably 0.045~0.055.
[0009] The thickness of the GaN substrate is 1~3 μm.
[0010] Re x Mo 1-x The thickness of the S2 layer is 18~20 nm.
[0011] The thickness of the Al2O3 buffer layer is 40~60 nm.
[0012] The electrode is made of Ti / Au. The electrode thickness is 50~70 nm / 50~70 nm.
[0013] The GaN substrate comprises, from bottom to top, a Si(111) substrate, an LT-AlN buffer layer, an HT-AlN buffer layer, a GaN nucleation layer, and a GaN thin film layer.
[0014] The thickness of the LT-AlN buffer layer is 80~120nm, the thickness of the HT-AlN buffer layer is 80~120nm, the thickness of the GaN nucleation layer is 180~220nm, and the thickness of the GaN thin film layer is 1200~1500nm.
[0015] The deposition temperature for preparing the LT-AlN buffer layer is 840~860℃.
[0016] The deposition temperature for preparing the HT-AlN buffer layer is 1030~1070℃.
[0017] The Re x Mo 1-x The S2 layer was prepared using the following method:
[0018] A clean substrate and mixture are placed in the downstream temperature zone of the chemical vapor deposition apparatus, while sulfur powder is placed in the upstream temperature zone. After purging the air, the gas pressure is adjusted, and the downstream temperature zone is heated from room temperature to 700-750 °C at a rate of 15-25 °C / min. Once the downstream temperature zone reaches 700-750 °C, the upstream temperature zone is heated to 200-250 °C at a rate of 8-12 °C / min, while simultaneously introducing a carrier gas. The reaction is allowed to proceed for 5-15 minutes, resulting in Re deposited on the substrate. x Mo 1-x S2 layer; remove the substrate and apply Re x Mo 1-x The S2 layer is transferred to the Al2O3 buffer layer.
[0019] In the downstream temperature zone, the clean substrate is located downstream, and the mixture is located upstream. A carrier gas is introduced, and the gas flows from the sulfur powder in the upstream temperature zone to the mixture in the downstream temperature zone, and then to the substrate.
[0020] The carrier gas flow rate is 165~185 sccm.
[0021] The mixture consists of rhenium source ReO3, molybdenum source MoO3 powder, and NaCl.
[0022] The mass ratio of rhenium source ReO3, molybdenum source MoO3 powder, and NaCl in the mixture is (3.5~5):(1~3):1, preferably 4:(1~3):1, and more preferably 4:(1.5~2.5):1.
[0023] The mass ratio of rhenium source ReO3 to sulfur powder is 4: (131~200).
[0024] Regulating air pressure refers to introducing carrier gas to make the ambient air pressure 145~155 Torr.
[0025] Re x Mo 1-x The substrates used in the fabrication of the S2 layer are SiO2 / Si substrate, mica, and sapphire substrate.
[0026] The Re x Mo 1-x The S2 layer is obtained through the following method:
[0027] (1) Place the clean substrate in the middle of a semi-open or open-end quartz boat or crucible, and then place a mixture of ReO3 powder, MoO3 powder and NaCl at a distance of 0.4~0.6 cm from one edge of the substrate. Push the quartz boat or crucible into the center of the downstream temperature zone of the CVD device. Place the sulfur powder into the quartz boat sealed at both ends and push it into the center of the upstream temperature zone of the CVD device. The placement positions of the materials from near the gas inlet to far away from the gas inlet are sulfur powder, mixture, and substrate.
[0028] (2) Ar gas is introduced to purge the air. After purging, Ar gas is continuously introduced until the pressure stabilizes at 145~155 Torr, and then the gas is stopped.
[0029] (3) The downstream temperature zone is heated from room temperature to 700-750 ℃ at a rate of 15-25 ℃ / min; when the downstream temperature zone reaches 700-750 ℃, the upstream temperature zone is heated to 200-250 ℃ at a rate of 8-12 ℃ / min, while a carrier gas is introduced. The reaction is carried out for 5-15 min, and Re is deposited on the substrate. x Mo 1-x S2 layer; remove the substrate and apply Re x Mo 1-x The S2 layer is transferred to the Al2O3 buffer layer.
[0030] The fabrication method of the molybdenum sulfide rhenium / GaN heterojunction ultraviolet photodiode includes the following steps:
[0031] S1. An LT-AlN buffer layer, an HT-AlN buffer layer, a GaN nucleation layer and a GaN thin film layer are sequentially deposited on a Si(111) substrate to obtain a GaN substrate.
[0032] S2. A portion of the upper surface area of the GaN thin film layer covering the GaN substrate is then deposited with an Al2O3 buffer layer in the uncovered area of the GaN thin film layer using an electron beam evaporation deposition process.
[0033] S3. Re x Mo 1-x The S2 layer was transferred onto the Al2O3 buffer layer;
[0034] S4. An electrode is provided on the upper surface portion of the GaN thin film layer not covered by the Al2O3 buffer layer, Re x Mo 1-x Electrodes are provided on the upper surface of the S2 layer.
[0035] In step S1, the Si(111) substrate is cleaned. Specifically, a cleaning solution is prepared by mixing 98% H2SO4 solution, 30 wt% H2O2 solution and water in a volume ratio of 3:3:1. The Si(111) substrate is then immersed in the cleaning solution for 0.5~1.5 h. After cleaning, the substrate is transferred to a 5% HF solution for a second cleaning. Then, water is used to remove the residual cleaning solution on the surface and the substrate is dried.
[0036] The specific steps of step S1 are as follows: Place the Si(111) substrate into the PLD chamber, and then... (4.5~5.5)×10... -10 Annealing at Pa and 840~860 °C for 0.8~1.2 h to remove residual stress on the surface; then, using a single crystal AlN template, an LT-AlN buffer layer is deposited on the surface of the Si(111) substrate at a deposition temperature of 840~860 °C; then, the Si(111) substrate with the pre-deposited LT-AlN layer is transferred into the MOCVD chamber, and an HT-AlN buffer layer is deposited using a single crystal AlN template at a deposition temperature of 1030~1070 °C; the MOCVD equipment is then used to deposit a GaN nucleation layer on the HT-AlN buffer layer, and a GaN thin film layer is grown on the nucleation layer at a deposition temperature of 1030~1070 °C.
[0037] In step S3, Re x Mo 1-x The S2 layer was prepared using the following method:
[0038] A clean substrate and mixture are placed in the downstream temperature zone of the chemical vapor deposition apparatus, while sulfur powder is placed in the upstream temperature zone. After purging the air, the gas pressure is adjusted, and the downstream temperature zone is heated from room temperature to 700-750 °C at a rate of 15-25 °C / min. Once the downstream temperature zone reaches 700-750 °C, the upstream temperature zone is heated to 200-250 °C at a rate of 8-12 °C / min, while simultaneously introducing a carrier gas. The reaction is allowed to proceed for 5-15 minutes, resulting in Re deposited on the substrate. x Mo 1-x S2 layer, substrate removed.
[0039] The removal of the substrate refers to the removal of Re deposited on the substrate. x Mo 1-x The surface of the S2 layer is uniformly coated with a 15-25% (w / w) polymethyl methacrylate (PMMA) solution, homogenized, cured, treated with a 5-10% (w / w) HF solution, and the substrate is peeled off. Homogenization conditions: first 350-370 rpm for 8-12 s, then 3500-3700 rpm for 25-35 s. Curing conditions: 115-125℃ for 12-20 min.
[0040] The transfer mentioned in step S3 refers to removing the substrate and then using a Si wafer to retrieve the thin film, with the PAAM surface in contact with the Si wafer. 1-x Mo x The S2 layer did not contact the Si wafer, and then Re was applied. 1-x Mo x One side of the S2 layer was transferred to the GaN thin film layer on the GaN substrate. The Si wafer was removed by water removal, and the water was removed. The wafer was then heat-treated at 145~155℃ for 15~25 min. The PMMA was removed by acetone immersion. The wafer was then rinsed with anhydrous ethanol and water sequentially for 10~20 min and dried.
[0041] After the transfer is completed in step S3, the GaN substrate is rapidly annealed at 175~185℃ in an N2 atmosphere for 4~6 min.
[0042] The electrode mentioned in step S4 can be a patterned electrode, specifically: an electrode on the surface of the GaN thin film layer not covered by the Al2O3 buffer layer and a Re... x Mo 1-x AZ 7133 positive photoresist was spin-coated onto the upper surface of layer S2, cured, exposed, developed, electrodes were deposited by evaporation, the photoresist was removed, and the surface was cleaned with anhydrous ethanol and water.
[0043] The electrode was rapidly annealed at 250-350°C in a N2 atmosphere for 4-6 minutes.
[0044] The beneficial effects of this invention are:
[0045] (1) This invention combines the structural characteristics of 2D TMDC / 3D GaN and uses low-pressure CVD, low-temperature PLD combined with high-temperature MOCVD and wet transfer process to prepare 2D / 3D hybrid heterojunction with large size, which has guiding significance for the design and preparation of 2DTMD heterojunction with different structures.
[0046] (2) The photodiode fabricated based on this lateral heterojunction has a rectification ratio of approximately 10 at ±1V. 4 The turn-on voltage is approximately 0.54 V. The responsivity and specific detectivity were calculated at different power levels, with the highest responsivity and specific detectivity being 6.84 A / W and 1.34 × 10⁻⁶, respectively. 9 Jones offers a possible approach to breaking through the performance bottleneck of two-dimensional material optoelectronic devices.
[0047] (3) The 2D / 3D hybrid heterojunction material prepared by this invention still has reference value in the fields of visible light communication, photocatalysis, and solar cells. Attached Figure Description
[0048] Figure 1 Re prepared in Example 2 1-x Mox Physical image of S2 thin film;
[0049] Figure 2 Re prepared in Example 2 1-x Mo x Atomic force microscopy (AFM) characterization of the S2 thin film;
[0050] Figure 3 Re prepared in Example 2 1-x Mo x High-resolution transmission electron microscopy (HRTEM) images and selected area electron diffraction (SAED) patterns of S2 thin films;
[0051] Figure 4 Re in Example 2 1-x Mo x Re 4f fine spectrum of X-ray photoelectron spectroscopy (XPS) of S2 thin film;
[0052] Figure 5 Re in Example 2 1-x Mo x XPS Mo 3d fine spectra of S2 thin films;
[0053] Figure 6 Re in Example 2 1-x Mo x A comparison of the fine Re 4f XPS spectra of the S2 thin film with those of the undoped film;
[0054] Figure 7 Re in Example 2 1-x Mo x A comparison of the Raman spectrum of the S2 thin film with that of the undoped film;
[0055] Figure 8 Re in Example 2 1-x Mo x Schematic diagram of an S2 / GaN heterojunction ultraviolet photodiode; 1-GaN substrate, 2-Al2O3 buffer layer, 3-Re x Mo 1-x S2 layer, 4-1: negative electrode, 4-2: positive electrode;
[0056] Figure 9 Re in Example 2 1-x Mo x Raman spectral characterization of S2 / GaN heterojunction;
[0057] Figure 10 Re in Example 2 1-x Mo x Photoexcitation-free IV characteristic curves of S2 / GaN heterojunction photodiode;
[0058] Figure 11 Re in Example 2 1-x Mo x Photoresponse spectrum of S2 / GaN heterojunction photodiode;
[0059] Figure 12 Re in Example 2 1-x Mo x IV curves of S2 / GaN heterojunction photodiode under different powers of 365 nm light excitation;
[0060] Figure 13 Re in Example 2 1-x Mo x The responsivity R and specific detectivity D of S2 / GaN heterojunction photodiodes under different powers of 365 nm light excitation * The test image. Detailed Implementation
[0061] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.
[0062] A molybdenum sulfide rhenium / GaN heterojunction ultraviolet photodiode includes a GaN substrate, an Al2O3 buffer layer disposed on the GaN substrate, and Re on the Al2O3 buffer layer. x Mo 1-x S2 layer; the Al2O3 buffer layer partially covers the GaN substrate, Re x Mo 1-x The S2 layer covers the upper surface of the Al2O3 buffer layer; electrodes are located on the upper portion of the GaN substrate not covered by the Al2O3 buffer layer, Re x Mo 1-x Electrodes are provided on the upper part of the S2 layer.
[0063] Re x Mo 1-x In layer S2, x is 0.03~0.08, preferably 0.04~0.065, more preferably 0.04~0.06, and even more preferably 0.045~0.055.
[0064] The thickness of the GaN substrate is 1~3 μm.
[0065] Re x Mo 1-x The thickness of the S2 layer is 18~20 nm.
[0066] The thickness of the Al2O3 buffer layer is 40~60 nm.
[0067] The electrode is made of Ti / Au. The electrode thickness is 50~70 nm / 50~70 nm.
[0068] The GaN substrate, from bottom to top, includes a Si(111) substrate, an LT-AlN buffer layer, an HT-AlN buffer layer, a GaN nucleation layer, and a GaN thin film layer.
[0069] The thickness of the LT-AlN buffer layer is 80~120nm, the thickness of the HT-AlN buffer layer is 80~120nm, the thickness of the GaN nucleation layer is 180~220nm, and the thickness of the GaN thin film layer is 1200~1500nm.
[0070] The deposition temperature for preparing the LT-AlN buffer layer is 840~860℃.
[0071] The deposition temperature for preparing the HT-AlN buffer layer is 1030~1070℃.
[0072] Example 1
[0073] This embodiment provides a Re 1-x Mo x The fabrication method of S2 / GaN (x=0.038) heterojunction ultraviolet photodiode includes the following steps:
[0074] (1) Take a SiO2 / Si wafer with a thickness of about 300 nm ( <100> (Crystal orientation), and cut it into multiple 1 cm × 1 cm square pieces for later use;
[0075] (2) Place the 1 cm × 1 cm SiO2 / Si substrate from step (1) in acetone and clean it in boiling state for 20 min to remove organic residues on the surface; after the acetone cleaning is completed, immediately transfer the substrate to anhydrous ethanol and clean it with an ultrasonic cleaner at room temperature for 20 min to remove the acetone on the surface; after the anhydrous ethanol treatment is completed, transfer the substrate to deionized water and clean it with an ultrasonic cleaner at room temperature for 20 min to remove the anhydrous ethanol and other inorganic contaminants on the surface; finally, take out the substrate and immediately blow off the deionized water on the surface with an air gun.
[0076] (3) Thoroughly mix 4.0 mg ReO3 powder, 1.0 mg MoO3 powder and 1.0 mg NaCl particles to obtain a mixture; then place a clean SiO2 / Si substrate in the center of a quartz crucible that is 5 cm long, 1.5 cm wide, 0.5 cm high, and 1 mm thick with open ends. Place the mixture 0.5 cm from the right edge of the substrate and push it into the center of the downstream of the CVD device (the mixture is closer to the upstream sulfur powder). Take a quartz boat of the same size but sealed at both ends, weigh 150 mg of sublimed sulfur powder into it, and then push it into the center of the upstream of the CVD device, keeping the relative positions of the substrate, mixture and sulfur powder, with the sulfur powder close to the inlet of the carrier gas;
[0077] (4) Pump the gas pressure inside the CVD device to less than 1 Torr, and then introduce argon gas at a flow rate of 200 sccm for 20 minutes to remove the air from the CVD tube. After the gas washing is completed, stop the gas flow and increase the gas pressure to 150 Torr. Start the heating program and let the downstream temperature zone rise to 700°C at a rate of 20°C / min. At the same time, the upstream temperature zone is controlled by the program to not rise. The temperature is slowly increased from the high temperature of the downstream zone. When the downstream temperature zone reaches 700°C, open the gas valve to introduce argon gas at a rate of 175 sccm. At the same time, the upstream temperature zone starts to slowly rise to 200°C at a rate of 10°C / min. This temperature is maintained for 10 minutes to maintain growth. After the growth is completed, let the CVD device cool down to room temperature naturally before opening the device.
[0078] (5) Prepare a cleaning solution by mixing 98% H2SO4 solution, 30 wt% H2O2 solution and deionized water in a volume fraction ratio of 3:3:1. Immerse the Si(111) substrate in the solution for 1 h. After cleaning, transfer the substrate to a 5% HF solution for a second cleaning. Then remove the residual cleaning solution with deionized water and dry it. Place the cleaned Si(111) substrate into the PLD chamber and heat it at 5 × 10⁻⁶ ℃. -10 Annealing was performed at Pa and 850 °C for 1 h to remove residual stress on the surface; then, using a single-crystal AlN template made of 99.99% pure ceramic sintered AlN target, an LT-AlN buffer layer of about 100 nm was deposited on the surface of the Si(111) substrate at 850 °C; the Si(111) substrate with the pre-deposited LT-AlN layer was transferred into the MOCVD chamber, and an HT-AlN buffer layer of about 100 nm was deposited using the single-crystal AlN template (the temperature of the buffer layer deposition was 1050 °C); the MOCVD equipment was used to deposit a GaN nucleation layer of about 200 nm on the HT-AlN buffer layer, and then a GaN thin film layer of about 1300 nm thickness was grown on the nucleation layer. The entire MOCVD process was carried out at 1050 °C.
[0079] (6) Take the GaN substrate from step (5) (the GaN substrate includes a Si(111) substrate, an LT-AlN buffer layer, an HT-AlN buffer layer, a GaN nucleation layer and a GaN thin film layer), and then cover half of its area (0.5 cm × 1 cm) with an iron metal hard mask. Then, use an electron beam evaporation deposition process to deposit a 40~60 nm thick Al2O3 buffer layer on the uncovered area of the GaN thin film layer.
[0080] (7) Prepare a 5% (v / v) HF solution for later use; [The following text appears to be unrelated and possibly from a different source: "The Re grown in step (4)..."] 1-x Mo x The substrate surface of the S2 thin film was uniformly coated with a 20% (w / w) polymethyl methacrylate (PMMA) solution. Spin coater was used to thoroughly coat the film at two different speeds: 360 rpm for 10 s and 3600 rpm for 30 s. The film was then heat-cured at 120°C for 15 min. After cooling, the substrate was transferred to an HF solution for etching for approximately 20 s. The PMMA thin film sample was then gently peeled from the substrate surface in deionized water. A clean Si wafer was then used with the PMMA side facing down and the Re... 1-x Mo x The Si wafer was retrieved with the "S2 on top" orientation and its surface moisture was absorbed using filter paper. Then, the Si wafer was placed face down on a cut 1 cm × 1 cm GaN substrate and transferred to another petri dish containing deionized water to detach the Si wafer. The surface of the GaN substrate, especially the edges of the transfer film, was then absorbed with filter paper until the film was completely adhered to the substrate. The substrate was then fixed at 150°C for 20 min. If any samples were found to be not adhered properly during heating, a heavy object wrapped in lint-free paper was used to press down on the surface for 5–10 min to help them adhere. After cooling, the substrate was placed in acetone, anhydrous ethanol, and deionized water for 1–1.5 hours, 15 min, and 15 min respectively, then dried at 100°C and rapidly annealed at 180°C in a N2 atmosphere for 5 min. This process successfully transferred the doped film to the Al2O3-coated GaN substrate.
[0081] (8) Take the sample from step (7), spin-coat AZ 7133 positive photoresist at a rotation speed and time setting of "3600 rpm, 30 s", and heat-cur it on a heating stage at 120℃ for 30 s; thereafter, use a special photoresist plate to expose it under xenon lamp irradiation for 100 s, and develop it in the developer for 20~30 s, and then transfer the sample to an electron beam evaporation coating device, where it is less than 1×10 -4 Under a vacuum of Pa, on the GaN surface and Re x Mo 1-xA negative electrode of 60 nm Ti / 60 nm Au was deposited on the surface of S2, respectively. After the deposition was completed, the sample was placed in acetone to remove the photoresist and cleaned with anhydrous ethanol and deionized water.
[0082] (9) Take the sample from step (8) and place it in a vacuum rapid annealing apparatus. Anneal it at 300°C in a N2 atmosphere for 5 minutes to prepare Re. 1-x Mo x S2 / GaN (x=0.038) heterojunction-based photodiode device.
[0083] The diode prepared in this embodiment has a turn-on voltage of 0.91 V and a rectification ratio of 10. 2 The responsivity is 0.97 A / W, and the specific detectivity is 1.91 × 10⁻⁶. 8 Jones.
[0084] Example 2:
[0085] This embodiment provides a Re 1-x Mo x The fabrication method of S2 / GaN (x=0.05) heterojunction ultraviolet photodiode includes the following steps:
[0086] (1)~(2) Same as Example 1;
[0087] (3) Difference from Example 1: 4.0 mg ReO3 powder, 2.0 mg MoO3 powder and 1.0 mg NaCl particles were thoroughly mixed;
[0088] (4) Evacuate the gas pressure inside the CVD apparatus to less than 1 Torr, then introduce argon gas at a flow rate of 200 sccm for 20 minutes to purge the air from the CVD tube (60 mm × 1400 mm). After purging, stop the gas flow, increase the gas pressure to 150 Torr, and start the heating program, allowing the downstream temperature zone to rise to 700°C at a rate of 20°C / min, while the upstream temperature zone remains unheated under program control, with the temperature slowly increasing from the downstream high temperature. Then, once the downstream temperature zone reaches 700°C, open the gas valve to introduce argon gas at a flow rate of 175 sccm, while the upstream temperature zone begins to slowly heat up. Maintain this state for 10 minutes to sustain growth. After growth is complete, allow the CVD apparatus to cool naturally to room temperature before opening the apparatus to obtain the desired result. Figure 1 The large area Re shown x Mo 1-x S2 (x=0.05) thin film, through Figure 2 AFM characterization showed that its thickness was approximately 18.24 nm. Figure 3 HRTEM and Figure 4The SAED characterization showed obvious single-crystal characteristics;
[0089] (5)~(8) Same as Example 1;
[0090] (9) Take the sample from step 8 and place it in a vacuum rapid annealing apparatus. Anneal at 300°C for 5 min to prepare Re. 1-x Mo x S2 / GaN (x=0.05) heterojunction-based photodiode device.
[0091] The diode prepared in this embodiment has a turn-on voltage of 0.54V and a turn-on voltage of 10V. 4 The responsivity is 6.84 A / W, and the specific detectivity is 1.34 × 10⁻⁶. 9 Jones.
[0092] Example 3:
[0093] This embodiment provides a Re 1-x Mo x The fabrication method of S2 / GaN (x=0.065) heterojunction ultraviolet photodiode includes the following steps:
[0094] (1)~(2) Same as Example 1;
[0095] (3) Difference from Example 1: Weigh 4.0 mg ReO3 powder, 3.0 mg MoO3 powder and mix thoroughly with 1.0 mg NaCl particles;
[0096] (4)~(8) Same as Example 1;
[0097] (9) Take the sample from step 8 and place it in a vacuum rapid annealing apparatus. Anneal at 300°C for 5 min to prepare Re. 1-x Mo x S2 / GaN (x=0.065) heterojunction-based photodiode device.
[0098] The diode prepared in this embodiment has a turn-on voltage of 0.87 V and a turn-on voltage of 10 V. 2 The responsivity is 1.76 A / W, and the specific detectivity is 3.64 × 10⁻⁶. 8 Jones.
[0099] The Re prepared in this example 1-x Mo x The performance parameters of the S2 / GaN heterojunction ultraviolet photodiode can be found in Example 2.
[0100] Figure 1 Re prepared in Example 2 1-x Mo xA physical image of the S2 thin film. Figure 2 Re prepared in Example 2 1-x Mo x Atomic force microscopy (AFM) characterization of the S2 thin film. Figure 3 Re prepared in Example 2 1-x Mo x High-resolution transmission electron microscopy (HRTEM) images and selected area electron diffraction (SAED) patterns of S2 thin films. Figure 4 Re in Example 2 1-x Mo x Re 4f fine spectrum of X-ray photoelectron spectroscopy (XPS) of S2 thin film. Figure 5 Re in Example 2 1-x Mo x Fine Mo 3d spectra of S2 thin films obtained by XPS. Figure 6 Re in Example 2 1-x Mo x A comparison of the fine Re 4f XPS spectra of the S2 thin film with those of the undoped film. Figure 7 Re in Example 2 1-x Mo x A comparison of the Raman spectrum of the S2 thin film with that of the undoped film.
[0101] Figure 8 Re in Example 2 1-x Mo x Schematic diagram of an S2 / GaN heterojunction ultraviolet photodiode; 1-GaN substrate, 2-Al2O3 buffer layer, 3-Re x Mo 1-x S2 layer, 4-1: negative electrode, 4-2: positive electrode.
[0102] The schematic diagram of the molybdenum sulfide rhenium / GaN heterojunction ultraviolet photodiode is shown below. Figure 8 As shown, it includes a GaN substrate 1, an Al2O3 buffer layer 2 disposed on the GaN substrate, and a Re layer disposed on the Al2O3 buffer layer. x Mo 1-x S2 layer 3; the Al2O3 buffer layer 2 partially covers the GaN substrate 1, Re x Mo 1-x S2 layer 3 covers the upper surface of Al2O3 buffer layer 2; the upper part of GaN substrate 1, which is not covered by Al2O3 buffer layer 2, is provided with electrodes 4-2, Re x Mo 1-x Electrode 4-1 is provided on the upper part of layer S2.
[0103] Figure 9 Re in Example 2 1-x Mo xRaman spectral characterization of S2 / GaN heterojunction. Figure 10 Re in Example 2 1- x Mo x Photoexcitation-free IV characteristic curves of S2 / GaN heterojunction photodiodes. Figure 11 Re in Example 2 1-x Mo x Photoresponse spectrum of S2 / GaN heterojunction photodiode.
[0104] Figure 12 Re in Example 2 1-x Mo x IV curves of S2 / GaN heterojunction photodiodes under different powers of 365 nm light excitation. Figure 13 Re in Example 2 1-x Mo x The responsivity R and specific detectivity D of S2 / GaN heterojunction photodiodes under different powers of 365 nm light excitation * The test image.
[0105] from Figure 3 It can be seen that the crystal still has crystallographic integrity after doping, and doping does not introduce obvious second phase precipitation or large-area amorphization / severe lattice collapse. Figure 4 , 5 6. It can be concluded that the dopant element Mo was indeed introduced and was in a specific chemical valence state. The overall shift of the key peak position to the left after doping means that the electronic structure has been changed. Figure 7 This indicates that different doping concentrations cause the Raman peak to shift. The Raman peak shifts more significantly to the left as the concentration increases. This can indicate that the dopant element enters the material system and changes the original chemical bonding and electronic structure, but the main phase remains stable.
[0106] from Figure 9 It can be concluded that the peak position did not change significantly after the transfer. Tests at the heterojunction revealed that it has characteristic peaks of both materials, indicating that the device has good heterojunction characteristics. Figure 10 This refers to the IV characteristics of the device under dark conditions. The device's rectification-related data are: turn-on voltage 0.54 V, rectification ratio 10. 4 The device has good rectification characteristics; Figure 11 This indicates that the device has a broad spectral response, with the responsivity and specific detectivity being the highest at around 365 nm, which is consistent with the response band of GaN. The device still has a response at 600 nm, which is due to the broadening of the response band caused by the presence of ReS2. Figure 12IV tests were performed on the device under different light intensities. It was found that with the forward current remaining almost constant, the greater the light intensity, the greater the reverse current. This indicates that the device has good photoresponse characteristics and a stable photo-electric conversion relationship. Figure 13 The responsivity and specific detectivity were tested under 365 nm light. The results showed that the device's responsivity reached 6.84 A / W and its specific detectivity reached 1.34 × 10⁻⁶. 9 Jones indicates that the device has excellent performance.
[0107] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope disclosed in the present invention, based on the technical solution and inventive concept of the present invention, shall fall within the scope of protection of the present invention.
Claims
1. A molybdenum sulfide rhenium / GaN heterojunction ultraviolet photodiode, characterized in that: Includes a GaN substrate, an Al2O3 buffer layer disposed on the GaN substrate, and a Re layer disposed on the Al2O3 buffer layer. x Mo 1-x S2 layer; the Al2O3 buffer layer partially covers the GaN substrate, Re x Mo 1-x The S2 layer covers the upper surface of the Al2O3 buffer layer; electrodes are located on the upper portion of the GaN substrate not covered by the Al2O3 buffer layer, Re x Mo 1-x Electrodes are provided on the upper part of the S2 layer; Re x Mo 1-x In layer S2, x ranges from 0.03 to 0.
08.
2. The molybdenum sulfide rhenium / GaN heterojunction ultraviolet photodiode according to claim 1, characterized in that: The Re x Mo 1- x In layer S2, x ranges from 0.04 to 0.065; The thickness of the GaN substrate is 1~3 μm; Re x Mo 1-x The thickness of the S2 layer is 18~20 nm; The thickness of the Al2O3 buffer layer is 40~60 nm; The GaN substrate comprises, from bottom to top, a Si(111) substrate, an LT-AlN buffer layer, an HT-AlN buffer layer, a GaN nucleation layer, and a GaN thin film layer.
3. The molybdenum sulfide rhenium / GaN heterojunction ultraviolet photodiode according to claim 2, characterized in that: The Re x Mo 1- x In layer S2, x ranges from 0.04 to 0.06; The deposition temperature for preparing the LT-AlN buffer layer is 840~860℃; The deposition temperature for preparing the HT-AlN buffer layer is 1030~1070℃.
4. The molybdenum sulfide rhenium / GaN heterojunction ultraviolet photodiode according to claim 3, characterized in that: The Re x Mo 1- x In layer S2, x ranges from 0.045 to 0.055; The thickness of the LT-AlN buffer layer is 80~120nm, the thickness of the HT-AlN buffer layer is 80~120nm, the thickness of the GaN nucleation layer is 180~220nm, and the thickness of the GaN thin film layer is 1200~1500nm.
5. The molybdenum sulfide rhenium / GaN heterojunction ultraviolet photodiode according to claim 1, characterized in that... : The electrode is made of Ti / Au; the electrode thickness is 50~70 nm / 50~70 nm. The Re x Mo 1-x The S2 layer was prepared using the following method: A clean substrate and mixture are placed in the downstream temperature zone of the chemical vapor deposition apparatus, while sulfur powder is placed in the upstream temperature zone. After purging the air, the gas pressure is adjusted, and the downstream temperature zone is heated from room temperature to 700-750 °C at a rate of 15-25 °C / min. Once the downstream temperature zone reaches 700-750 °C, the upstream temperature zone is heated to 200-250 °C at a rate of 8-12 °C / min, while simultaneously introducing a carrier gas. The reaction is allowed to proceed for 5-15 minutes, resulting in Re deposited on the substrate. x Mo 1-x S2 layer; remove the substrate and apply Re x Mo 1-x The S2 layer is transferred onto the Al2O3 buffer layer; the mixture consists of ReO3, molybdenum source MoO3 powder, and NaCl.
6. The molybdenum sulfide rhenium / GaN heterojunction ultraviolet photodiode according to claim 5, characterized in that: In the downstream temperature zone, the clean substrate is located downstream and the mixture is located upstream; a carrier gas is introduced, and the gas flow is from the sulfur powder in the upstream temperature zone to the mixture in the downstream temperature zone, and then to the substrate; The flow rate of the carrier gas is 165~185 sccm; The mass ratio of rhenium source ReO3, molybdenum source MoO3 powder to NaCl in the mixture is (3.5~5):(1~3):1; The mass ratio of rhenium source ReO3 to sulfur powder in the mixture is 4:(131~200); The aforementioned regulating air pressure refers to introducing carrier gas to make the ambient air pressure 145~155 Torr; Re x Mo 1-x The substrates used in the fabrication of the S2 layer are SiO2 / Si substrate, mica, and sapphire substrate.
7. The molybdenum sulfide rhenium / GaN heterojunction ultraviolet photodiode according to claim 6, characterized in that: The mass ratio of the rhenium source ReO3, the molybdenum source MoO3 powder, and NaCl is 4:(1~3):
1.
8. The molybdenum sulfide rhenium / GaN heterojunction ultraviolet photodiode according to claim 5, characterized in that: The Re x Mo 1-x The S2 layer is obtained through the following method: (1) Place the clean substrate in the middle of a semi-open or open-end quartz boat or crucible, and then place a mixture of ReO3 powder, MoO3 powder and NaCl at a distance of 0.4~0.6 cm from one edge of the substrate. Push the quartz boat or crucible into the center of the downstream temperature zone of the CVD device. Place the sulfur powder into the quartz boat sealed at both ends and push it into the center of the upstream temperature zone of the CVD device. The placement positions of the materials from near the gas inlet to far away from the gas inlet are sulfur powder, mixture, and substrate. (2) Ar gas is introduced to purge the air. After purging, Ar gas is continuously introduced until the pressure stabilizes at 145~155 Torr, and then the gas is stopped. (3) The downstream temperature zone is heated from room temperature to 700-750 ℃ at a rate of 15-25 ℃ / min; when the downstream temperature zone reaches 700-750 ℃, the upstream temperature zone is heated to 200-250 ℃ at a rate of 8-12 ℃ / min, while a carrier gas is introduced. The reaction is carried out for 5-15 min, and Re is deposited on the substrate. x Mo 1-x S2 layer; remove the substrate and apply Re x Mo 1-x The S2 layer is transferred to the Al2O3 buffer layer.
9. The method for fabricating a molybdenum sulfide rhenium / GaN heterojunction ultraviolet photodiode according to any one of claims 1 to 8, characterized in that: Includes the following steps: S1. An LT-AlN buffer layer, an HT-AlN buffer layer, a GaN nucleation layer and a GaN thin film layer are sequentially deposited on a Si(111) substrate to obtain a GaN substrate. S2. A portion of the upper surface area of the GaN thin film layer covering the GaN substrate is then deposited with an Al2O3 buffer layer in the uncovered area of the GaN thin film layer using an electron beam evaporation deposition process. S3. Re x Mo 1-x The S2 layer was transferred onto the Al2O3 buffer layer; S4. An electrode is provided on the upper surface portion of the GaN thin film layer not covered by the Al2O3 buffer layer, Re x Mo 1-x Electrodes are provided on the upper surface of the S2 layer.
10. The method for fabricating a molybdenum sulfide rhenium / GaN heterojunction ultraviolet photodiode according to claim 9, characterized in that: The specific steps of step S1 are as follows: Place the Si(111) substrate into the PLD chamber, and then... (4.5~5.5)×10... -10 Annealing at Pa and 840~860℃ for 0.8~1.2 h to remove residual stress on the surface; then using a single crystal AlN template, an LT-AlN buffer layer is deposited on the surface of the Si(111) substrate at a deposition temperature of 840~860℃. Subsequently, the Si(111) substrate with the pre-deposited LT-AlN layer was transferred into the MOCVD chamber, and an HT-AlN buffer layer was deposited using a single-crystal AlN template at a deposition temperature of 1030~1070℃. The MOCVD equipment was then used to deposit a GaN nucleation layer on the HT-AlN buffer layer, and a GaN thin film layer was grown on the nucleation layer at a deposition temperature of 1030~1070℃. After the transfer is completed in step S3, the GaN substrate is rapidly annealed at 175~185℃ in an N2 atmosphere for 4~6 min; The electrode mentioned in step S4 is a patterned electrode; The electrode was rapidly annealed at 250-350°C in a N2 atmosphere for 4-6 minutes.