A method for oxygen vacancy control in Ga2O3 thin films based on vertical electric field modulation

Abstract

This invention discloses a method for oxygen vacancy control in Ga2O3 thin films based on vertical electric field modulation, belonging to the field of photoelectric conversion semiconductor materials. The method includes: 1) Ga2O3 thin film and device fabrication, 2) ionic liquid droplet addition, and 3) application of a vertical electric field for modulation. This invention achieves oxygen vacancy position modulation in Ga2O3 thin films through the action of a strong electric field, deepening the controllability of the photoelectric conversion performance of Ga2O3 thin films and demonstrating new possibilities for the construction and application of Ga2O3 thin film photodetectors. This invention not only provides a new approach and direction for solving the current difficulties of low response frequency and high static power consumption in Ga2O3 thin films, but also offers strong controllability, high modulation efficiency, and quantifiability, making it highly applicable.

Description

Technical Field

[0001] This invention relates to the field of photoelectric conversion semiconductor materials, specifically to a method for oxygen vacancy control of Ga2O3 thin films based on vertical electric field modulation. Background Technology

[0002] Ultraviolet (UV) detectors have significant applications in missile tracking, flame detection, and deep space imaging, making them a focus of intense research and development. Currently, commercially available UV photodetectors are typically bulky and fragile photomultiplier tubes (PMTs), requiring external high-voltage bias, which limits their applications. Ga₂O₃, with its wide bandgap, high radiation intensity, inherent solar-blind absorption, and stable physicochemical properties, is an ideal photosensitive layer material for solar-blind (cutoff wavelength ~280 nm) detection and is considered a potential replacement for PMTs.

[0003] Ga2O3, as the fourth-generation semiconductor material most likely to quickly overcome industrialization bottlenecks, is expected to completely replace silicon carbide and gallium nitride in the market within the next 10 years. Currently, Ga2O3-based deep ultraviolet (DUV) detectors have made significant progress in material screening and device structure, with research focus gradually shifting from mechanism exploration to practical applications. However, before large-scale application, Ga2O3-based DUV detectors still face several core challenges, such as slow device response speed, low photoresponsivity, high static power consumption, and low integration density. These issues present numerous scientific and technological challenges. Currently, UV detectors based on single-crystal Ga2O3 materials face problems such as high cost, small scale, and difficulty in isolation. In contrast, polycrystalline Ga2O3 is easy to prepare and has low cost, giving it rich compatibility and design freedom for various applications. However, developing high-performance UV detectors with high environmental tolerance based on polycrystalline Ga2O3 materials still requires addressing issues such as poor material stability, high defect density, large leakage current, and significant persistent photoconductivity. Therefore, it is necessary to develop high-quality Ga2O3 thin films with simple preparation processes and low defect density to improve device performance.

[0004] Furthermore, the photoelectric properties of Ga2O3 thin films are significantly modulated by the distribution of oxygen vacancies within them. Introducing an appropriate amount of oxygen vacancies into Ga2O3 can increase its carrier concentration, resulting in higher photoconductivity gain and superior photodetection capabilities. However, in photoconductive Ga2O3 photodetectors, defect-related photoconductivity gain and sustained photoconductivity increase responsivity and response recovery time, respectively, creating a contradictory relationship between responsivity and response recovery speed. Therefore, developing precise techniques for controlling the distribution of oxygen vacancies in thin films is crucial for constructing high-performance ultraviolet detectors. Thus, a simple and efficient method for controlling oxygen vacancies in Ga2O3 thin films is needed. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for oxygen vacancy control of Ga2O3 thin films based on vertical electric field modulation. This method involves adding an ionic liquid to the Ga2O3 thin film and applying a voltage, thereby controlling the oxygen vacancy migration under the action of the electric field. This not only deepens the ability to control the photoelectric conversion performance of Ga2O3 semiconductor thin films, but also provides new ideas and directions for the construction and application of Ga2O3 thin film photoelectric conversion devices.

[0006] This invention first provides a method for controlling oxygen vacancies in Ga2O3 thin films using a vertical electric field, comprising the following steps:

[0007] Step 1): Prepare a Ga2O3 thin film on the upper surface of the SiO2 / Si substrate; scrape off the SiO2 layer on the bottom part of the SiO2 / Si substrate and connect the exposed Si to the PCB board as the bottom gate electrode; fix the PCB board on the probe stage, which is a four-probe stage, wherein the source probe and drain probe provide the source-drain voltage V. SD The top gate probe and bottom gate probe provide the gate voltage V. G Gold electrodes were fabricated by sputtering gold electrode channels onto the upper surface of the Ga2O3 thin film using photolithography and sputtering techniques.

[0008] Step 2): An organic cationic salt ionic liquid is dropped onto the Ga2O3 thin film to form an ionic liquid film;

[0009] Step 3): Insert the top gate probe of the probe stage into the ionic liquid film without contacting the Ga2O3 film; apply voltage to the Ga2O3 film through the bottom electrode and the top gate probe, and the ionic liquid film generates a strong vertical electric field, thereby controlling the migration of oxygen vacancies in the Ga2O3 film.

[0010] Furthermore, the voltage applied when the top gate probe is connected to the positive terminal of the power supply and the bottom gate probe is connected to the negative terminal is a positive voltage; the applied voltage in step 3) is: first apply a positive voltage with a duration of 1-3 minutes and an amplitude of 1-5V, and then apply a negative voltage with a duration of 1-5 seconds and an amplitude of 1-5V.

[0011] The present invention also claims protection for a photodetector obtained by the method described above, wherein the photodetector comprises at least a gold electrode, a Ga2O3 thin film and a SiO2 / Si substrate from top to bottom.

[0012] Compared with the prior art, the present invention has the following beneficial technical effects:

[0013] The method of this invention does not involve complex equipment connections or numerous steps. The control device only requires one source meter, which is technically simple, easy to operate, and has better scalability.

[0014] The method described in this invention can precisely and effectively control the oxygen vacancy distribution in Ga2O3, improve device performance, and effectively solve the problem of the contradictory relationship between responsivity and response recovery speed in current Ga2O3 photodetectors.

[0015] This invention uses an ionic liquid as the gate material, which possesses strong charge control capabilities. Traditional gate materials have weak carrier control capabilities (<10-10). 13 cm -2 It is difficult to control the carrier concentration of correlated electron oxides (~10). 14 cm -2 Effective regulation is achieved. In the ionic liquid structure of this invention, the potential mainly drops off on the electric double layer with a thickness of about 1 nm at the liquid / solid interface, corresponding to a carrier concentration higher than 10. 14 -10 15 cm -2 It can enable the control of the optoelectronic properties of devices made of various materials, including Ga2O3. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the apparatus for the oxygen vacancy control method of Ga2O3 thin film of the present invention;

[0017] Figure 2 This is a schematic diagram of the fabrication steps of the device on the Ga2O3 thin film of the present invention;

[0018] Figure 3 This is a time-current (IT) curve of the device on the Ga2O3 thin film before and after modulation in Embodiment 1 of the present invention;

[0019] Figure 4 This is a time-current (IT) curve of the device on the Ga2O3 thin film before and after modulation in Embodiment 2 of the present invention;

[0020] Figure 5 This is a time-current (IT) curve of the device on the Ga2O3 thin film before and after modulation in Embodiment 3 of the present invention. Detailed Implementation

[0021] The present invention will be further described and illustrated below with reference to specific embodiments. The embodiments described are merely examples of the content of this disclosure and do not limit the scope of the invention. The technical features of each embodiment in the present invention can be combined accordingly, provided that there is no mutual conflict.

[0022] To further illustrate the technical means of this invention, the specific implementation steps and details of the method of this invention will be described in detail.

[0023] The method for controlling oxygen vacancies in Ga2O3 thin films provided by the present invention includes the following steps in sequence: (1) preparation of Ga2O3 thin films and devices, (2) addition of ionic liquid, and (3) control by applying a vertical electric field.

[0024] like Figure 1 As shown, in one embodiment of the present invention, step (1) includes: preparing a Ga2O3 thin film on the upper surface of a SiO2 / Si substrate; scraping off the SiO2 layer on the bottom part of the SiO2 / Si substrate using a wafer cutter, and connecting the exposed Si to a PCB board via liquid metal InGa as a bottom gate electrode; fixing the PCB board to a probe stage with insulating tape; the probe stage in this embodiment is a four-probe stage, wherein the source probe and the drain probe provide the source-drain voltage V. SD The top gate probe and bottom gate probe provide the gate voltage V. G The present invention uses photolithography and sputtering technology to sputter gold electrode channels on the upper surface of the Ga2O3 thin film to prepare gold electrodes.

[0025] In this embodiment, the Ga2O3 thin film is prepared by atomic layer deposition (ALD), and gold electrodes are further prepared on the Ga2O3 thin film using photolithography and sputtering techniques. Preferably, the thickness of the Ga2O3 thin film is 50-150 nm.

[0026] like Figure 2 As shown, in a specific embodiment of the present invention, a gold electrode is fabricated using photolithography and sputtering techniques. The specific steps are as follows:

[0027] 1.1) Spin-coating photoresist onto a Ga2O3 thin film;

[0028] 1.2) Cover the interdigitated electrode photomask on the photoresist and expose it;

[0029] 1.3) Place the exposed sample in the developer solution for development, and then blow it dry;

[0030] 1.4) A thermal evaporation coating machine was used to prepare the gold electrode. The coating pressure was set to 1 Pa and the evaporation current was 40-50 A. The gold electrode channel was sputtered out according to the development trace to prepare the gold electrode. The thickness of the gold electrode was 50-100 nm. After the electrode preparation was completed, the adhesive was removed and the electrode was dried.

[0031] In one embodiment of the present invention, step (2) includes: dropping an organic cation salt ionic liquid onto the Ga2O3 film body to form an ionic liquid film, wherein the area of ​​the ionic liquid film is smaller than the area of ​​the Ga2O3 film body and only covers the gold electrode channel portion.

[0032] The organic cation salt ionic liquid has a mass percentage concentration of 95% to 99%, and preferably, the organic cation salt ionic liquid is C8H. 11 F6N3O4S2, C 10 H 19 F6N2P and C8H 15 A mixture of one or more of N2F6P, with an ionic liquid membrane thickness of 1–2.5 mm.

[0033] In one embodiment of the present invention, step (3) includes: inserting the top gate probe of the probe stage into the ionic liquid film without contacting the main body of the Ga2O3 film; applying a voltage source to the Ga2O3 film through the bottom electrode and the top gate probe, thereby generating a strong vertical electric field in the ionic liquid film, which modulates the migration of oxygen vacancies within the Ga2O3 film. The present invention can control this migration through the source-drain voltage V. SD The device performance was tested and adjusted using optical pulses.

[0034] In a specific embodiment of the present invention, the voltage applied when the top gate probe is connected to the positive terminal of the power supply and the bottom gate probe is connected to the negative terminal is a positive voltage; the applied voltage in step 3) is: first apply a positive voltage with a duration of 1-3 minutes and an amplitude of 1-5V, and then apply a negative voltage with a duration of 1-5 seconds and an amplitude of 1-5V.

[0035] The voltage application process must not damage the main body of the Ga2O3 film; the applied voltage is a continuous DC voltage, and the oxygen vacancies in the Ga2O3 film are migrated under the action of the strong electric field generated by the ionic liquid, thereby regulating the sample performance.

[0036] Example 1:

[0037] like Figure 1 As shown, a SiO2 / Si substrate is used.

[0038] Step (1) Preparation of Ga2O3 thin film and device: First, a high-quality Ga2O3 semiconductor thin film with excellent crystallinity and low defect density is prepared on SiO2 / Si substrate by atomic layer deposition (ALD);

[0039] Subsequently, a metal-semiconductor-metal (MSM) photodetector was fabricated on a Ga2O3 thin film using photolithography and evaporation processes. The specific steps of this process are as follows: Figure 2As shown, firstly, photoresist was spin-coated onto a Ga2O3 thin film using a KW-4A spin coater at 1000 rpm (6 s) and 5000 rpm (20 s), followed by pre-baking on a 90℃ heating plate for 3 min to obtain a uniform photoresist coating. Next, an interdigitated electrode photomask was placed over the photoresist-coated sample for exposure (3 s), followed by development in a developer (30 s) and then dried. Finally, Au electrodes were prepared using a thermal evaporation deposition machine, with a deposition pressure of 1 Pa, an evaporation current of 45 A, and an Au film thickness of 60 nm. After electrode preparation, the sample was ultrasonically removed in acetone at 60 W for approximately 30 s and then dried with N2 gas.

[0040] Step (2) Ionic liquid addition: An organic cation salt ionic liquid is added dropwise to the Ga2O3 film substrate to form an ionic liquid film. The area of ​​the ionic liquid film is smaller than the area of ​​the Ga2O3 film substrate, covering only the gold electrode channel portion of the Ga2O3 film. The ionic liquid is a salt that is liquid at room temperature or near room temperature and is composed entirely of organic cations and inorganic or organic anions. In step (2) above, the ionic liquid concentration is 97%, and the ionic liquid selected is C8H4. 11 F6N3O4S2, the thickness of the ionic liquid membrane is 2mm.

[0041] Step (3) Vertical electric field modulation: Insert the probe of the probe stage into the ionic liquid film without contacting the main body of the Ga2O3 film; connect the negative terminal of the source meter to the bottom electrode and the positive terminal of the source meter to the probe; after applying a 5V voltage to the source meter, the ionic liquid generates a strong electric field, causing oxygen vacancies in the Ga2O3 film to migrate and complete the performance modulation. The main body of the Ga2O3 film must not be damaged during the voltage application process; the applied voltage is a continuous DC voltage, and the duration is 1 minute.

[0042] test:

[0043] (1) The photoelectrochemical performance of the Ga2O3 thin film before and after treatment was tested. The time-current (IT) curves obtained at a source-drain voltage of 2V are shown in the figure. Figure 3 As shown, the performance of the samples was good before and after treatment, and the photocurrent and dark current of the device were reduced after the adjustment.

[0044] Example 2:

[0045] The difference between this embodiment and Implementation 1 is that the DC voltage value of the vertical electric field modulation process in step (3) is -5V; the photoelectrochemical performance of the Ga2O3 thin film before and after treatment is tested, and the time-current (IT) curve obtained at a source-drain voltage of 2V is shown in the figure. Figure 4 As shown, the photocurrent and dark current of the device both increased after regulation.

[0046] Example 3:

[0047] The difference between this embodiment and Implementation 1 is that, in step (3) of the vertical electric field modulation process, a +5V DC voltage is applied for 1 minute, followed by a -5V DC voltage for 1 second. The photoelectrochemical performance of the Ga2O3 thin film before and after treatment is tested, and the time-current (IT) curve obtained at a source-drain voltage of 2V is shown in the figure. Figure 4 As shown, the photocurrent of the device increases while the dark current decreases after modulation, resulting in a significant performance improvement.

[0048] The oxygen vacancy control method for Ga2O3 thin films described in Examples 1-3 of this invention features a simple Ga2O3 thin film structure and equipment, and a convenient device fabrication process. This invention avoids complex equipment connections and numerous steps; the control device only requires a source meter, resulting in low technical difficulty, simple operation, and greater scalability.

[0049] The oxygen vacancy control method for Ga2O3 thin films described in Examples 1-3 of this invention, in photoconductive Ga2O3 photodetectors, increases responsivity and response recovery time due to defect-related photoconductivity gain and sustained photoconductivity, respectively, creating a contradictory relationship between responsivity and response recovery speed. Therefore, precise control of the oxygen vacancy distribution in Ga2O3 is crucial for improving device performance. Traditional gate material field-effect structures have weak carrier control capabilities and struggle to control carrier concentrations (~10) in correlated electron oxides. 14 cm -2 Effective regulation can be achieved. Ionic liquids are used as the regulation material. In the ionic liquid-gated structure, the potential mainly drops off on the approximately 1 nm thick electric double layer at the liquid / solid interface, corresponding to a carrier concentration higher than 10. 14 -10 15 cm -2 This allows for the control of the metal-insulator transition in various materials, including transition metal oxides. Furthermore, the strong electric field at the interface between the ionic liquid and the transition metal oxide induces the migration of oxygen ions, leading to changes in physical properties.

[0050] The oxygen vacancy control methods for Ga2O3 thin films described in Examples 1-3 of this invention are time-efficient and highly effective. Compared to methods that control oxygen vacancies through the field-effect structure of traditional gate materials, which require sophisticated equipment and involve complex steps, the methods described in this invention are simple to operate, involve fewer steps, are faster, and offer higher efficiency in controlling device performance.

[0051] The above-described embodiments are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. Those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for oxygen vacancy control in Ga2O3 thin films based on vertical electric field modulation, characterized in that, Includes the following steps: Step 1): Prepare a Ga2O3 thin film on the upper surface of the SiO2 / Si substrate; scrape off the SiO2 layer on the bottom part of the SiO2 / Si substrate and connect the exposed Si to the PCB board as the bottom gate electrode; fix the PCB board on the probe stage, which is a four-probe stage, wherein the source probe and drain probe provide the source-drain voltage V. SD The top gate probe and bottom gate probe provide the gate voltage V. G Gold electrodes were fabricated by sputtering gold electrode channels onto the upper surface of the Ga2O3 thin film using photolithography and sputtering techniques. Step 2): An organic cationic salt ionic liquid is dropped onto the Ga2O3 thin film to form an ionic liquid film; Step 3): Insert the top gate probe of the probe stage into the ionic liquid film without contacting the Ga2O3 film; apply voltage to the Ga2O3 film through the bottom gate electrode and the top gate probe, and the ionic liquid film generates a strong vertical electric field, thereby controlling the migration of oxygen vacancies in the Ga2O3 film.

2. The method according to claim 1, characterized in that, The thickness of the Ga2O3 film in step 1) is 50-150 nm.

3. The method according to claim 1, characterized in that, In step 1), the Ga2O3 thin film is prepared on a SiO2 / Si substrate by atomic layer deposition.

4. The method according to claim 1, characterized in that, The exposed Si in step 1) is connected to the PCB board by liquid metal, which is InGa.

5. The method according to claim 1, characterized in that, Step 1) involves using photolithography and sputtering techniques to sputter gold electrode channels onto the Ga2O3 thin film to fabricate a gold electrode, and includes the following sub-steps: 1.1) Spin-coating photoresist onto a Ga2O3 thin film; 1.2) Cover the interdigitated electrode photomask on the photoresist and expose it; 1.3) Place the exposed sample in the developer solution for development, and then blow it dry; 1.4) A thermal evaporation coating machine was used to prepare the gold electrode. The coating pressure was set to 1 Pa and the evaporation current was 40-50 A. The gold electrode channel was sputtered out according to the development trace to prepare the gold electrode. The thickness of the gold electrode was 50-100 nm. After the electrode preparation was completed, the adhesive was removed and the electrode was dried.

6. The method according to claim 1, characterized in that, The organic cation salt ionic liquid in step 2) has a mass percentage concentration of 95% to 99%, and the organic cation salt ionic liquid is C8H. 11 F6N3O4S2, C 10 H 19 F6N2P and C8H 15 The ionic liquid membrane is a mixture of one or more of N2F6P, and its thickness is 1 to 2.5 mm.

7. The method according to claim 5, characterized in that, In step 2), the area of ​​the ionic liquid film only covers the channel portion of the gold electrode.

8. The method according to claim 1, characterized in that, When the top gate probe is connected to the positive terminal of the power supply and the bottom gate probe is connected to the negative terminal, the voltage applied is positive. The applied voltage in step 3) is: first apply a positive voltage with a duration of 1-3 minutes and an amplitude of 1-5V, and then apply a negative voltage with a duration of 1-5 seconds and an amplitude of 1-5V.

9. The method according to claim 1, characterized in that, In step 3), through the source-drain voltage V SD The device performance was tested and adjusted using optical pulses.

10. A photodetector obtained by the method of any one of claims 1-9, wherein the photodetector comprises, from top to bottom, at least a gold electrode, a Ga2O3 thin film obtained by the method of any one of claims 1-9, and a SiO2 / Si substrate.

Images