Solar-blind ultraviolet photoelectric detector based on beta-phase gallium oxide nanorod and preparation method of solar-blind ultraviolet photoelectric detector
By growing β-phase gallium oxide nanorods on SiO2/Si substrates and then subjecting them to argon plasma treatment and oxygen annealing, the problems of high cost and low carrier concentration of noble metal catalysts were solved, and a solar-blind ultraviolet photodetector with high PDCR value and fast response was realized.
Patent Information
- Application Number
- CN202511026879.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-24
- Publication Date
- 2025-10-28
AI Technical Summary
The existing preparation methods of gallium oxide nanorods have the problems of high cost of using precious metal catalysts and catalytic residues affecting device performance. In addition, the low carrier concentration leads to a long response time of the photodetector and a low PDCR value.
β-phase gallium oxide nanorods were grown on SiO2/Si substrates using low-pressure chemical vapor deposition. Surface impurities were removed and oxygen vacancies were introduced through argon plasma surface modification and oxygen annealing, which optimized the metal-semiconductor interface contact, reduced dark current, and improved the PDCR value.
Stable growth of high-quality β-phase gallium oxide nanorods was achieved, which improved the sensitivity and stability of photodetectors, reduced the fabrication cost, and resulted in high PDCR values, fast response speed and low dark current, making them suitable for large-scale industrial production.
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Figure CN120857690A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of ultra-wide bandgap semiconductor technology, and particularly relates to a solar-blind ultraviolet photodetector based on β-phase gallium oxide nanorods and its fabrication method. Background Technology
[0002] Gallium oxide, as an ultrawide bandgap semiconductor, has shown great potential in power electronic devices and deep ultraviolet photodetectors due to its excellent thermal stability, high breakdown field strength, and deep ultraviolet optical properties. In particular, gallium oxide in one-dimensional nanostructures (such as nanowires and nanorods) is considered an ideal material for improving the performance of solar-blind ultraviolet photodetectors due to its high specific surface area, quantum confinement effect, and excellent carrier transport properties.
[0003] Compared with general epitaxial thin films, one-dimensional gallium oxide nanostructures have higher crystal quality and abundant surface active sites, which can significantly enhance gas sensing sensitivity and photoresponse speed. However, gallium oxide nanorods are usually synthesized by hydrothermal methods or noble metal catalysis. In recent years, chemical vapor deposition technology has become a research hotspot for gallium oxide nanostructure growth due to its advantages of controllable crystal quality and tunable morphology. Jia C (JIA CY, JEON DW, XU JL, et al. Catalyst-Assisted Large-Area Growth of Single-Crystal β-Ga2O3 Nanowires on Sapphire Substrates by Metal–Organic Chemical VaporDeposition[J]. Nanomaterials, 2020, 10(6): 1031.) et al. synthesized high-density β-Ga2O3 nanowires on sapphire substrates using gold nanocrystal seeds via MOCVD. However, the use of noble metal catalysts leads to high costs, and catalytic residues may interfere with the device interface performance. Sheoran (Sheoran, Hardhyan, Shi Fang, Fangzhou Liang, Zhe Huang, Shuchi Kaushik, Nethala Manikanthababu, Xiaolong Zhao, Haiding Sun, Rajendra Singh and Shibing Long. 2022. "High Performance of Zero-Power-Consumption MOCVD-Grownβ-Ga2O3-Based Solar-Blind Photodetectors with Ultralow Dark Current and High-Temperature Functionalities". ACS Applied Materials & Interfaces 14(46):52096–107.) et al. used MOCVD-grown β-phase gallium oxide to fabricate an MSM-type photodetector. Although the PDCR was high, the rise time was as high as 0.69 s at a 10 V bias due to the unintentionally low carrier concentration. Summary of the Invention
[0004] To overcome the shortcomings of the prior art, the present invention aims to provide a solar-blind ultraviolet photodetector based on β-phase gallium oxide nanorods and its fabrication method. Through a chemical vapor deposition process without noble metal catalysts, a stepwise atmosphere regulation method is employed, first introducing argon gas for heating and then introducing oxygen, to suppress premature nucleation at low temperatures, promote the stable growth of ordered nanorods, and optimize the oxidation reaction kinetics between the gallium source and oxygen. This allows for the efficient direct growth of a β-phase gallium oxide film with a nanorod morphology on a SiO2 / Si substrate. Furthermore, argon plasma activation of the nanorod film surface before metal electrode deposition removes surface impurities and introduces appropriate oxygen vacancies, reducing the Schottky barrier and improving the metal-semiconductor interface contact. After metal electrode deposition, localized oxygen annealing is performed on the uncovered metal electrode area to passivate deep oxygen vacancies, reduce dark current, and thereby improve the PDCR value, enhance the device's sensitivity to ultraviolet light, and improve device stability.
[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0006] A method for fabricating a solar-blind ultraviolet photodetector based on β-phase gallium oxide nanorods includes the following steps:
[0007] Step 1: Using low-pressure chemical vapor deposition, solid metallic gallium is used as a reaction precursor to grow β-phase gallium oxide nanorods on a SiO2 / Si substrate to obtain β-phase gallium oxide nanorod thin films.
[0008] Step 2: Perform argon plasma surface modification treatment on the β-phase gallium oxide nanorod film;
[0009] Step 3: Deposit a metal electrode on the modified β-phase gallium oxide nanorod film to fabricate a solar-blind ultraviolet photodetector, and then perform high-temperature oxygen annealing.
[0010] In step 1, the β-phase gallium oxide nanorod film has a nanorod structure with a diameter of 160nm-860nm and a length of 1um-2.8um.
[0011] In step 1, the growth process of the β-phase gallium oxide nanorod film is as follows:
[0012] Step 1.1: Place solid gallium metal as the reaction precursor in a single-tube LPCVD furnace. Place the cleaned SiO2 / Si substrate downstream of the reaction precursor, parallel to the gas flow direction. Both are in the same temperature zone of the single-tube LPCVD furnace, with a height difference of 2-3 cm and a horizontal distance of 3-7 cm.
[0013] Step 1.2: Argon gas is introduced into the cleaned single-tube LPCVD tube furnace. After the furnace pressure stabilizes at 100±10Pa, the metal gallium and SiO2 / Si substrate are heated. When the temperature reaches the growth temperature, oxygen is introduced to grow β-phase gallium oxide nanorods.
[0014] The purity of the solid gallium metal is greater than or equal to 99.999%.
[0015] The flow rates of argon and oxygen are 180-220 sccm and 10-40 sccm, respectively.
[0016] The heating conditions for the single-tube CVD tube furnace are as follows: the temperature zone is heated to 900-960℃ at a rate of 18-20℃ / min. After the temperature in the temperature zone reaches the set value, it is held for 20-40 minutes. After the holding period, it is allowed to cool naturally to room temperature.
[0017] In step 2, the argon plasma treatment process is as follows: the β-phase gallium oxide film is subjected to argon plasma treatment for 60-120 seconds at a flow rate of 80-100 sccm and a pressure of 5-15 Pa, with a power of 30-50 W.
[0018] In step 3, a metal electrode is deposited on the β-phase gallium oxide nanorod thin film using a vacuum evaporation process.
[0019] In step 3, the annealing temperature is 400-450℃, the time is 20-30 min, and the oxygen flow rate is 30-40 sccm.
[0020] The present invention also provides a solar-blind ultraviolet photodetector prepared by the above-mentioned method for preparing a solar-blind ultraviolet photodetector based on β-phase gallium oxide nanorods.
[0021] Compared with the prior art, the present invention has the following beneficial effects:
[0022] 1. This invention achieves stable growth of single β-phase gallium oxide nanorods by using a low-pressure chemical vapor deposition process to introduce oxygen after reaching the growth temperature and utilizing the gas-solid (VS) mechanism to react with oxygen after the gallium precursor is vaporized, thereby suppressing α / γ phase hybridization.
[0023] 2. This invention employs low-pressure chemical vapor deposition. The lattice mismatch between the SiO2 / Si substrate and gallium oxide promotes island growth, exhibiting an anisotropic growth trend of nanorods. The high specific surface area of the nanorods leads to a higher PDCR value in the device.
[0024] 3. Compared with traditional vapor deposition, which requires complex precursors (such as GaCl3) and is prone to introducing halogen residues, this invention does not require a halogenation process or precious metal catalysis, has better impurity control, and has no organic waste gas emissions.
[0025] 4. This invention provides a method for fabricating a solar-blind ultraviolet photodetector by plasma processing-electrode deposition-oxygen annealing. While reducing contact resistance, oxygen annealing improves deep-level defects. While maintaining a high PDCR, it also maintains a fast rise rate and a fast fall rate. The high PDCR ensures extremely high sensitivity and anti-interference capability to ultraviolet light, and the fast response speed ensures that the device can track short-time signals.
[0026] In summary, the β-phase gallium oxide nanorod thin film prepared by low-pressure chemical vapor deposition in this invention has high quality, and the solar-blind ultraviolet photodetector prepared by following the process sequence of plasma treatment-electrode deposition-oxygen annealing of the β-phase gallium oxide nanorod thin film has the characteristics of high PDCR value, fast response speed, simple preparation method and low preparation cost, and can be prepared on a large scale for industrial use. Attached Figure Description
[0027] Figure 1 This is a schematic diagram of a single-tube LPCVD tubular furnace.
[0028] Figure 2 This is a schematic diagram of the structure of the solar-blind ultraviolet photodetector prepared according to the present invention.
[0029] In the diagram: 1. Metallic gold; 2. Metallic chromium; 3. β-phase gallium oxide layer; 4. SiO2 layer; 5. Si layer.
[0030] Figure 3 The images shown are optical microscope and SEM images of the β-phase gallium oxide nanorod thin film prepared in Example 3. Figure 3 (a) is an optical microscope image. Figure 3 (b) is a SEM image.
[0031] Figure 4 This is a SEM image of the sample prepared in Comparative Example 1.
[0032] Figure 5 This is a SEM image of the sample prepared in Comparative Example 2.
[0033] Figure 6 This is a SEM image of the sample prepared in Comparative Example 3.
[0034] Figure 7 The images show the Raman shift spectra of the β-phase gallium oxide nanorod thin film prepared in Example 3 before and after argon plasma treatment. Figure 7 (a) is the Raman displacement spectrum before processing. Figure 7 (b) is the processed Raman displacement spectrum.
[0035] Figure 8The XRD patterns of the β-phase gallium oxide nanorod film prepared in Example 3 before and after argon plasma treatment are shown below. Figure 8 (a) is the XRD pattern before processing. Figure 8 (b) is the processed XRD pattern.
[0036] Figure 9 The X-ray photoelectron spectra of the β-phase gallium oxide nanorod thin film prepared in Example 3 before and after argon plasma treatment are shown below. Figure 9 (a) is the X-ray photoelectron spectrum before processing. Figure 9 (b) is the X-ray photoelectron spectrum after processing.
[0037] Figure 10 The image shows the IV characteristic curves of solar-blind ultraviolet photodetectors processed using different techniques under different illumination conditions. Figure 10 (a) shows the IV characteristic curves of a solar-blind ultraviolet photodetector fabricated by depositing electrodes only on a β-phase gallium oxide nanorod thin film. Figure 10 (b) is the IV characteristic curve of the solar-blind ultraviolet photodetector prepared in Example 3.
[0038] Figure 11 The IT curve of the solar-blind ultraviolet photodetector prepared in Example 3 after applying an ultraviolet light pulse.
[0039] Figure 12 The IV characteristic curves of Comparative Example 3 under different lighting conditions are shown.
[0040] Figure 13 The IV characteristic curves for Comparative Example 4 are shown under different lighting conditions. Detailed Implementation
[0041] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer shall apply.
[0042] A method for fabricating a solar-blind ultraviolet photodetector based on β-phase gallium oxide nanorods includes the following steps:
[0043] Step 1: Using a low-pressure chemical vapor deposition process, solid metallic gallium is used as a reaction precursor to grow β-phase gallium oxide on a SiO2 / Si substrate to obtain a β-phase gallium oxide thin film; the β-phase gallium oxide thin film has a nanorod structure with a diameter of 160nm-860nm and a length of 1um-2.8um.
[0044] Step 1.1: As Figure 1As shown, solid gallium metal is placed as a reaction precursor inside an alumina boat in a single-tube LPCVD furnace. A cleaned SiO2 / Si substrate is placed downstream of the reaction precursor, parallel to the gas flow direction. Both are located in the same temperature zone of the single-tube LPCVD furnace, with a height difference of 2-3 cm and a horizontal distance of 3-7 cm. The purity of the solid gallium metal is greater than or equal to 99.999%. The cleaning process of the SiO2 / Si substrate involves sequentially ultrasonically cleaning it in NMP, isopropanol, and deionized water for 10 min, followed by drying.
[0045] Step 1.2: Argon gas is introduced into the cleaned single-tube LPCVD tube furnace, and the mechanical pump is turned on. After the furnace pressure stabilizes at 100±10Pa, the metal gallium and SiO2 / Si substrate are heated. When the temperature reaches the growth temperature, oxygen is introduced to grow β-phase gallium oxide nanorods. The flow rates of the two carrier gases, argon and oxygen, are 180-220 sccm and 10-40 sccm, respectively.
[0046] The cleaning operation of the single-tube CVD tube furnace is as follows:
[0047] After sealing the single-tube CVD tube furnace, turn on the mechanical pump and wait until the vacuum degree inside the quartz tube is below 10Pa. Then turn off the mechanical pump, open the gas valve, and introduce 500-600 sccm of argon gas until the gas pressure inside the quartz tube returns to normal. Repeat the above operation three times to complete the cleaning.
[0048] The heating conditions of the single-tube CVD tube furnace are as follows: the temperature zone is heated to 900-960℃ at a rate of 18-20℃ / min. After the temperature in the temperature zone reaches the set value, it is held for 20-40 minutes, that is, the growth time is 20-40 minutes. After the holding time is over, it is naturally cooled to room temperature.
[0049] Step 2: Perform argon plasma (Ar-Plasma) surface modification treatment on the β-phase gallium oxide nanorod film to introduce oxygen vacancies on the surface, thereby reducing the Schottky barrier and improving subsequent metal-semiconductor contact;
[0050] The β-phase gallium oxide film was placed in a plasma cleaner and subjected to Ar-Plasma treatment for 60-120 seconds at a flow rate of 80-100 sccm and a pressure of 5-15 Pa, with a power of 30-50 W.
[0051] Step 3: Deposit a metal electrode on the modified β-phase gallium oxide nanorod film to fabricate an MSM-type solar-blind ultraviolet photodetector. Then, perform deep oxygen vacancy passivation on the β-phase gallium oxide nanorod film region without metal electrode coverage at 400-450℃ for 20-30 min to reduce dark current; the oxygen flow rate is 30-40 sccm.
[0052] The deposition process is as follows: a chromium-gold electrode is prepared by vacuum evaporation using a hard mask; wherein the thickness of the chromium-gold electrode is 20nm / 80nm, as shown below. Figure 2 As shown;
[0053] The oxygen high-temperature annealing process is as follows: a cleaned single-tube LPCVD tube furnace is used for high-temperature annealing. When the pressure inside the furnace drops to 10Pa, the temperature is increased. After the temperature reaches the annealing temperature, oxygen is introduced.
[0054] The present invention will be further described in detail below with reference to embodiments and comparative examples. The same processing technology will not be described again in the following specific embodiments.
[0055] Example 1
[0056] A method for fabricating a solar-blind ultraviolet photodetector based on β-phase gallium oxide nanorods includes the following steps:
[0057] Step 1: Solid gallium metal was placed as a reaction precursor inside an alumina boat. A cleaned SiO2 / Si substrate was placed downstream of the precursor, parallel to the gas flow direction. Both were placed in the same temperature zone of a single-tube LPCVD furnace, with a height difference of 2 cm and a horizontal distance of 3 cm. Argon gas was then introduced into the cleaned single-tube LPCVD furnace. After the furnace pressure stabilized at 100±10 Pa, the temperature zone was heated to 900 °C at a rate of 18 °C / min. Oxygen was then introduced, and the temperature was maintained for 20 min to grow a β-phase gallium oxide nanorod film. After the temperature maintenance, the film was allowed to cool naturally to room temperature. The flow rates of the two carrier gases, argon and oxygen, were 180 sccm and 40 sccm, respectively.
[0058] Step 2: Ar-Plasma surface modification treatment of β-phase gallium oxide nanorod film was carried out using argon gas at a flow rate of 80 sccm and a pressure of 5 Pa for 120 s and a power of 30 W.
[0059] Step 3: Deposit a chromium-gold electrode on the treated β-phase gallium oxide nanorod film, and then anneal it at 400°C with oxygen for 20 min at an oxygen flow rate of 30 sccm to obtain a solar-blind ultraviolet photodetector based on β-phase gallium oxide nanorods.
[0060] Example 2
[0061] A method for fabricating a solar-blind ultraviolet photodetector based on β-phase gallium oxide nanorods includes the following steps:
[0062] Step 1: Solid gallium metal was placed as the reaction precursor inside an alumina boat. The cleaned SiO2 / Si substrate was placed downstream of the precursor, parallel to the gas flow direction. Both were placed in the same temperature zone of a single-tube LPCVD furnace, with a height difference of 2 cm and a horizontal distance of 4 cm. Argon gas was then introduced into the cleaned single-tube LPCVD furnace. After the furnace pressure stabilized at 100±10 Pa, the temperature zone was heated to 915 °C at a rate of 18.3 °C / min. Oxygen was then introduced, and the temperature was maintained for 25 min to grow a β-phase gallium oxide nanorod film. After the temperature maintenance, the film was allowed to cool naturally to room temperature. The flow rates of the two carrier gases, argon and oxygen, were 190 sccm and 30 sccm, respectively.
[0063] Step 2: Ar-Plasma surface modification treatment of β-phase gallium oxide nanorod film was carried out using argon gas at a flow rate of 80 sccm and a pressure of 15 Pa for 120 s with a power of 30 W.
[0064] Step 3: Deposit a chromium-gold electrode on the treated β-phase gallium oxide nanorod film, and then anneal it at 430°C with oxygen for 20 min at an oxygen flow rate of 30 sccm to obtain a solar-blind ultraviolet photodetector based on β-phase gallium oxide nanorods.
[0065] Example 3
[0066] A method for fabricating a solar-blind ultraviolet photodetector based on β-phase gallium oxide nanorods includes the following steps:
[0067] Step 1: Solid gallium metal was placed as the reaction precursor inside an alumina boat. The cleaned SiO2 / Si substrate was placed downstream of the precursor, parallel to the gas flow direction. Both were placed in the same temperature zone of a single-tube LPCVD furnace, with a height difference of 3 cm and a horizontal distance of 5 cm. Argon gas was then introduced into the cleaned single-tube LPCVD furnace. After the furnace pressure stabilized at 100±10 Pa, the temperature zone was heated to 930 °C at a rate of 18.6 °C / min. Oxygen was then introduced, and the temperature was maintained for 30 min to grow a β-phase gallium oxide nanorod film. After the temperature maintenance, the film was allowed to cool naturally to room temperature. The flow rates of the two carrier gases, argon and oxygen, were 200 sccm and 30 sccm, respectively.
[0068] Step 2: Ar-Plasma surface modification treatment of β-phase gallium oxide nanorod film was carried out using argon gas at a flow rate of 90 sccm and a pressure of 10 Pa for 100 s with a power of 40 W.
[0069] Step 3: Deposit a chromium-gold electrode on the treated β-phase gallium oxide nanorod film, and then anneal it at 430°C with oxygen for 30 min at an oxygen flow rate of 35 sccm to obtain a solar-blind ultraviolet photodetector based on β-phase gallium oxide nanorods.
[0070] Example 4
[0071] A method for fabricating a solar-blind ultraviolet photodetector based on β-phase gallium oxide nanorods includes the following steps:
[0072] Step 1: Solid gallium metal was placed as a reaction precursor inside an alumina boat. A cleaned SiO2 / Si substrate was placed downstream of the precursor, parallel to the gas flow direction. Both were placed in the same temperature zone of a single-tube LPCVD furnace, with a height difference of 3 cm and a horizontal distance of 7 cm. Argon gas was then introduced into the cleaned single-tube LPCVD furnace. After the furnace pressure stabilized at 100±10 Pa, the temperature zone was heated to 950 °C at a rate of 19 °C / min. Oxygen was then introduced, and the temperature was maintained for 40 min to grow a β-phase gallium oxide nanorod film. After the temperature maintenance, the film was allowed to cool naturally to room temperature. The flow rates of the two carrier gases, argon and oxygen, were 210 sccm and 20 sccm, respectively.
[0073] Step 2: Ar-Plasma surface modification treatment of β-phase gallium oxide nanorod film was carried out using argon gas at a flow rate of 100 sccm and a pressure of 15 Pa for 90 s and a power of 50 W.
[0074] Step 3: Deposit a chromium-gold electrode on the treated β-phase gallium oxide nanorod film, and then anneal it at 450°C with oxygen for 25 min at an oxygen flow rate of 40 sccm to obtain a solar-blind ultraviolet photodetector based on β-phase gallium oxide nanorods.
[0075] Example 5
[0076] A method for fabricating a solar-blind ultraviolet photodetector based on β-phase gallium oxide nanorods includes the following steps:
[0077] Step 1: Solid gallium metal was placed as the reaction precursor inside an alumina boat. The cleaned SiO2 / Si substrate was placed downstream of the precursor, parallel to the gas flow direction. Both were placed in the same temperature zone of a single-tube LPCVD furnace, with a height difference of 3 cm and a horizontal distance of 7 cm. Argon gas was then introduced into the cleaned single-tube LPCVD furnace. After the furnace pressure stabilized at 100±10 Pa, the temperature zone was heated to 960 °C at a rate of 19.2 °C / min. Oxygen was then introduced, and the temperature was maintained for 40 min to grow a β-phase gallium oxide nanorod film. After the temperature maintenance, the film was allowed to cool naturally to room temperature. The flow rates of the two carrier gases, argon and oxygen, were 220 sccm and 10 sccm, respectively.
[0078] Step 2: Ar-Plasma surface modification treatment of β-phase gallium oxide nanorod film was carried out using argon gas at a flow rate of 100 sccm and a pressure of 15 Pa for 60 s and a power of 50 W.
[0079] Step 3: Deposit a chromium-gold electrode on the treated β-phase gallium oxide nanorod film, and then anneal it at 450°C with oxygen for 30 min at an oxygen flow rate of 40 sccm to obtain a solar-blind ultraviolet photodetector based on β-phase gallium oxide nanorods.
[0080] Figure 3 The morphology of the β-phase gallium oxide nanorods prepared in Example 3 is shown below. Figure 3 (a) Under an optical microscope Figure 3 (b) is shown under a SEM microscope; by Figure 3 (a) It can be seen that the β-phase gallium oxide film grown on the SiO2 / Si substrate is dense and uniform, with no visible cracks, pores, or pinpoint defects on the sample surface, indicating excellent stress control in the preparation method of this invention; Figure 3 (b) It can be seen that the β-phase gallium oxide film grown on the SiO2 / Si substrate has a nanorod structure and a very high specific surface area. This indicates that the use of low-pressure chemical vapor deposition with the gas flow sequence of first introducing argon and then oxygen ensures a stable supply of precursors and good oxidation ability, resulting in uniform nucleation density on the SiO2 / Si substrate. Furthermore, due to the lattice mismatch between the SiO2 / Si substrate and the β-phase gallium oxide, heterogeneous nucleation lacks epitaxial constraints, leading to anisotropic growth and ultimately forming an oriented one-dimensional nanorod structure.
[0081] Comparative Example 1
[0082] The steps and materials of Comparative Example 1 are the same as those of Example 4, except that in step 1, the distance between the gallium source and the SiO2 / Si substrate is 9 cm. Figure 4 As shown, the surface is covered with a large number of tiny flake-like, rod-like, and prismatic particles of varying sizes, resulting in a rather chaotic morphology. The film grown in this proportion cannot form a dense and uniform nanorod morphology. This phenomenon is mainly attributed to insufficient flux of gallium precursor to the substrate surface, leading to reduced nucleation density and limited directional growth.
[0083] Comparative Example 2
[0084] The steps and materials of Comparative Example 2 and Example 3 are the same, except that in step 1, a mixture of oxygen and argon gas is introduced immediately after the heating begins, instead of introducing oxygen only after the growth temperature is reached. Figure 5As shown, a large number of disordered, stacked sheet-like and rod-like structures grow on the surface of the product. This phenomenon is attributed to the premature nucleation of the surface by oxygen at low temperatures, resulting in dense nucleation sites, restricted directional growth, and the generation of a large number of structural defects.
[0085] Comparative Example 3
[0086] Comparative Example 3 uses the same steps and materials as Example 3, except that in step 1, the growth temperature is set to 970°C. Figure 6 As shown, the surface of the product is a mixture of highly entangled nanowires, nanoribbons and thin sheets. Its formation mechanism lies in the severe imbalance between the nucleation rate and the growth rate at high temperature.
[0087] The electrical performance of the solar-blind ultraviolet photodetector prepared in Comparative Example 3 was tested, and its IV characteristic curves under dark conditions and 254 nm ultraviolet illumination are shown below. Figure 12 As shown. Figure 12 It can be seen that the photocurrent value of Comparative Example 3 reaches 4 × 10⁻⁶ under a 10V bias voltage. -6 A, the photocurrent value is similar to that of Example 3 under the same bias voltage. Although the photocurrent value of the solar-blind ultraviolet photodetector with nanorod structure under 254nm ultraviolet illumination is similar to that of the non-nanorod structure, its dark current value is significantly reduced. This is because the nanorod array has a high specific surface area and a natural current-limiting effect, which can improve the light absorption rate and significantly suppress the transport and leakage current of dark-state carriers, thereby greatly improving the PDCR value of the device.
[0088] Comparative Example 4
[0089] Comparative Example 4 uses the same steps and materials as Example 3, except that it does not undergo argon plasma treatment. Instead, a chromium-gold electrode is directly deposited on the β-phase gallium oxide nanorod film, followed by high-temperature oxygen annealing to obtain a solar-blind ultraviolet photodetector based on β-phase gallium oxide nanorods. The IV characteristic curves of the solar-blind ultraviolet photodetector prepared in this comparative example under dark conditions and 254nm ultraviolet illumination are shown below. Figure 13 As shown. Figure 13 It can be seen that, under a 10V bias voltage, the photocurrent and dark current values of this comparative example are 1.2 × 10⁻⁶. -6 A and 2×10 -10A. The PDCR value, calculated as (photocurrent - dark current) / dark current, is 600. The solar-blind ultraviolet photodetector prepared from β-phase gallium oxide nanorod films without argon plasma surface treatment exhibits significantly higher dark current than the solar-blind ultraviolet photodetector prepared using plasma treatment in Example 3, due to the presence of numerous traps and leakage channels at the interface. However, the photocurrent value is not significantly improved, resulting in a lower PDCR value. In contrast, argon plasma treatment significantly improves the surface cleanliness and metal-semiconductor contact performance, greatly suppresses dark current, and significantly increases the PDCR to 1.5 × 10⁻⁶. 4 .
[0090] Figure 7 The images show the Raman shift spectra of the β-phase gallium oxide nanorod thin film prepared in Example 3 before and after argon plasma treatment. Figure 7 (a) is the sample before processing. Figure 7 (b) shows the processed sample. It can be seen that at 145.51 cm... -1 172.58cm -1 201.24cm -1 349.34cm -1 417.81cm -1 522.91cm -1 656.67cm -1 766.55cm -1 There are distinct peaks at various points, except for the one at 520.35cm. -1 The peak at position 1 is a characteristic peak of SiO2. The other peak positions are consistent with the standard spectrum of monoclinic β-phase gallium oxide (space group C2 / m) reported in the literature, indicating that the main body of the film is a single β phase and the peak positions do not change significantly before and after treatment.
[0091] Figure 8 The images shown are XRD patterns of the β-phase gallium oxide nanorod film prepared in Example 3 before and after argon plasma treatment. Figure 8 (a) is the sample before processing. Figure 8 (b) shows the processed sample. It can be seen that obvious characteristic peaks appear at 18.9°, 30.4°, 31.7°, 33.4°, 38.4°, 43.0°, 45.8°, 54.5°, and 56.49°, which are consistent with the peak positions of β-phase gallium oxide, and there is no significant change in the peak positions before and after the treatment.
[0092] Figure 9 The X-ray photoelectron spectra of the β-phase gallium oxide nanorod thin film prepared in Example 3 before and after argon plasma treatment are shown below. Figure 9 (a) is the sample before processing. Figure 9 (b) shows the processed sample. O in the figure ⅠO represents lattice oxygen and is a major component of the stoichiometry of substances. Ⅱ This indicates the location of oxygen vacancy defects in the crystal lattice. Figure 9 It can be seen that after argon plasma treatment, the area occupied by oxygen vacancies increases significantly. The presence of vacancies reduces the Schottky barrier, thereby improving the ohmic contact.
[0093] Figure 10 The graph shows a comparison of the current of solar-blind ultraviolet photodetectors processed with different techniques under dark conditions and 254nm ultraviolet light. Figure 10 (a) shows the IV characteristic curves of a solar-blind ultraviolet photodetector fabricated by depositing electrodes only on a β-phase gallium oxide nanorod thin film. Figure 10 (b) shows the IV characteristic curves of the solar-blind ultraviolet photodetector prepared in Example 3. Figure 10 (a) It can be seen that the photocurrent and dark current of the β-phase gallium oxide nanorod film with only the electrode deposited are 2.2 × 10⁻⁶ under a bias voltage of 10 V. -6 and 4×10 -8 Its PDCR value is only 54 at a bias voltage of 10V; after argon plasma treatment and oxygen annealing after electrode fabrication, the surface metal-semiconductor contact is improved. Furthermore, due to the reduction of deep oxygen vacancies in the β-phase gallium oxide nanorod film region not covering the metal electrode after oxygen annealing, the dark current value is significantly reduced to 3.5×10. -11 However, the photocurrent value is 5.4 × 10⁻⁶. -7 The magnitude did not change significantly, resulting in a PDCR value of 1.54 × 10⁻⁶ at a 10V bias. 4 It improved by approximately 280 times compared to before treatment.
[0094] Figure 11 The image shows the It curve of the solar-blind photodetector prepared in Example 3 after applying a 254nm ultraviolet light pulse. It can be seen that the rise time of the solar-blind photodetector prepared in this invention is 0.30s, and the fall time is 1.28s. Figure 10 It can be seen that, while maintaining a high PDCR (>1.5×10), 4 Under the premise of maintaining a rise rate of 0.3s and a fall rate of 1.28s, the high PDCR ensures extremely high sensitivity and anti-interference capability to ultraviolet light, and the fast response speed ensures that the device can track short-term signals.
Claims
1. A method for fabricating a solar-blind ultraviolet photodetector based on β-phase gallium oxide nanorods, characterized in that, The steps include: Step 1: Using low-pressure chemical vapor deposition, solid metallic gallium is used as a reaction precursor to grow β-phase gallium oxide nanorods on a SiO2 / Si substrate to obtain β-phase gallium oxide nanorod thin films. Step 2: Perform argon plasma surface modification treatment on the β-phase gallium oxide nanorod film; Step 3: Deposit a metal electrode on the modified β-phase gallium oxide nanorod film to fabricate a solar-blind ultraviolet photodetector, and then perform high-temperature oxygen annealing.
2. The method for fabricating a solar-blind ultraviolet photodetector based on β-phase gallium oxide nanorods according to claim 1, characterized in that, In step 1, the β-phase gallium oxide nanorod film has a nanorod structure with a diameter of 160nm-860nm and a length of 1um-2.8um.
3. The method for fabricating a solar-blind ultraviolet photodetector based on β-phase gallium oxide nanorods according to claim 1, characterized in that, In step 1, the growth process of the β-phase gallium oxide nanorod film is as follows: Step 1.1: Place solid gallium metal as the reaction precursor in a single-tube LPCVD furnace. Place the cleaned SiO2 / Si substrate downstream of the reaction precursor, parallel to the gas flow direction. Both are in the same temperature zone of the single-tube LPCVD furnace, with a height difference of 2-3 cm and a horizontal distance of 3-7 cm. Step 1.2: Argon gas is introduced into the cleaned single-tube LPCVD tube furnace. After the furnace pressure stabilizes at 100±10Pa, the metal gallium and SiO2 / Si substrate are heated. When the temperature reaches the growth temperature, oxygen is introduced to grow β-phase gallium oxide nanorods.
4. The method for fabricating a solar-blind ultraviolet photodetector based on β-phase gallium oxide nanorods according to claim 1, characterized in that: The purity of the solid gallium metal is greater than or equal to 99.999%.
5. The method for fabricating a solar-blind ultraviolet photodetector based on β-phase gallium oxide nanorods according to claim 3, characterized in that: The flow rates of argon and oxygen are 180-220 sccm and 10-40 sccm, respectively.
6. The method for fabricating a solar-blind ultraviolet photodetector based on β-phase gallium oxide nanorods according to claim 3, characterized in that, The heating conditions for the single-tube CVD tube furnace are as follows: the temperature zone is heated to 900-960℃ at a rate of 18-20℃ / min. After the temperature in the temperature zone reaches the set value, it is held for 20-40 minutes. After the holding period, it is allowed to cool naturally to room temperature.
7. The method for fabricating a solar-blind ultraviolet photodetector based on β-phase gallium oxide nanorods according to claim 1, characterized in that: In step 2, the argon plasma treatment process is as follows: the β-phase gallium oxide film is subjected to argon plasma treatment for 60-120 seconds at a flow rate of 80-100 sccm and a pressure of 5-15 Pa, with a power of 30-50 W.
8. The method for fabricating a solar-blind ultraviolet photodetector based on β-phase gallium oxide nanorods according to claim 1, characterized in that: In step 3, a metal electrode is deposited on the β-phase gallium oxide nanorod thin film using a vacuum evaporation process.
9. The method for fabricating a solar-blind ultraviolet photodetector based on β-phase gallium oxide nanorods according to claim 1, characterized in that: In step 3, the annealing temperature is 400-450℃, the time is 20-30 min, and the oxygen flow rate is 30-40 sccm.
10. A solar-blind ultraviolet photodetector prepared by the method for preparing a solar-blind ultraviolet photodetector based on β-phase gallium oxide nanorods as described in claims 1-9.