Ga2O3 film oxygen vacancy regulation and control method based on vertical electric field regulation and control

Abstract

The invention discloses an oxygen vacancy regulation and control method of a Ga2O3 film based on vertical electric field regulation and control, and belongs to the field of photoelectric conversion semiconductor materials. The method comprises the steps of (1) preparing a Ga2O3 film and a device, (2) dropwise adding ionic liquid, and (3) applying a vertical electric field for regulation and control. According to the invention, the oxygen vacancy position adjustment of the Ga2O3 thin film is realized through the action of a strong electric field, the regulation and control capability of the photoelectric conversion performance of the Ga2O3 thin film is deepened, and new possibility is provided for the construction and application of a Ga2O3 thin film photoelectric detector. The invention not only provides a new thought and a new direction for solving the problems of low response frequency and high static power consumption of the existing Ga2O3 film, but also has the advantages of strong controllability, high regulation and control efficiency, quantifiability and stronger generalization performance.

Description

Technical Field

[0001] The present invention relates to the field of photoelectric conversion semiconductor materials, and in particular to a method for regulating oxygen vacancies in a Ga2O3 film based on vertical electric field regulation. Background Art

[0002] Ultraviolet detectors have important application value in the fields of missile tracking, flame detection and deep space imaging, and are the focus of competitive research and development. Currently, commercial ultraviolet photodetectors are usually bulky and fragile photomultiplier tubes that require external high-voltage bias, which limits their applications. Ga2O3 is an ideal photosensitive layer material for solar-blind (cut-off wavelength ~280nm) detection due to its wide bandgap, high radiation intensity, inherent solar-blind absorption, and stable physical and chemical properties. It is considered a potential substitute for photomultiplier tubes.

[0003] As the material that is most likely to quickly solve the technical bottleneck of industrialization among the fourth-generation semiconductor materials, Ga2O3 is expected to completely replace the silicon carbide and gallium nitride markets in the next 10 years. At present, Ga2O3-based deep ultraviolet detectors have made some important progress in material screening and device structure, and the research focus has gradually shifted from mechanism exploration to practical application. However, before large-scale application, Ga2O3-based deep ultraviolet detectors still have some core problems that need to be solved, such as slow device response speed, low photoresponsivity, high static power consumption, and low integration. These problems are faced with a large number of scientific problems and technical challenges. At present, ultraviolet detectors based on single-crystal Ga2O3 materials face problems such as high cost, small scale, and difficulty in isolation. In contrast, polycrystalline Ga2O3 has the characteristics of easy preparation and low cost, which makes it have rich compatibility and design freedom for different application scenarios. However, the development of high-performance ultraviolet detectors with high environmental tolerance based on polycrystalline Ga2O3 materials still needs to solve the problems of poor material stability, high defect density, large leakage current, and obvious continuous photoconductivity effect. Therefore, it is necessary to develop high-quality Ga2O3 films with simple preparation process and low defect density to improve device performance.

[0004] In addition, the photoelectric properties of Ga2O3 films are significantly regulated by the distribution of oxygen vacancies in them. Introducing an appropriate amount of oxygen vacancies in Ga2O3 can increase its carrier concentration, giving it a higher photoconductivity gain and excellent photodetection capability. However, in photoconductive Ga2O3 photodetectors, defect-related photoconductivity gain and sustained photoconductivity increase the responsivity and response recovery time, respectively, resulting in a mutually restrictive and contradictory relationship between the responsivity and the response recovery speed. It can be seen that developing precise control technology for the distribution of oxygen vacancies in thin films is the key to building high-performance ultraviolet detectors. Therefore, a method for regulating oxygen vacancies in Ga2O3 films that is simple to operate and highly efficient is needed. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for regulating oxygen vacancy in Ga2O3 thin film based on vertical electric field regulation. The method achieves oxygen vacancy regulation in Ga2O3 thin film by dripping ionic liquid on the Ga2O3 thin film and applying voltage, utilizing oxygen vacancy migration under the action of an electric field. This method not only deepens the ability to regulate 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] The present invention first provides a method for regulating oxygen vacancies in Ga2O3 thin films by vertical electric field, comprising the following steps:

[0007] Step 1): Prepare a Ga2O3 film on the upper surface of a SiO2 / Si substrate; scrape off the SiO2 layer on the bottom surface of the SiO2 / Si substrate, and connect the exposed Si portion to a PCB board as a bottom gate electrode; fix the PCB board on a probe workbench, which is a four-probe workbench, wherein a source probe and a drain probe provide a source-drain voltage V SD , the top gate probe and the bottom gate probe provide the gate voltage V G ; Sputtering a gold electrode channel on the upper surface of the Ga2O3 film using photolithography and sputtering technology to prepare a gold electrode;

[0008] Step 2): adding an organic cationic salt ionic liquid dropwise onto the Ga2O3 film to form an ionic liquid film;

[0009] Step 3): insert the top gate probe of the probe workbench into the ionic liquid film without contacting the Ga2O3 film; a voltage source applies 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, so that the migration of oxygen vacancies in the Ga2O3 film is regulated.

[0010] Furthermore, the voltage applied when the top gate probe is connected to the positive pole of the power supply and the bottom gate probe is connected to the negative pole 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 seeks to protect a photoelectric detector obtained by regulating the method, wherein the photoelectric detector comprises at least a gold electrode, a Ga2O3 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] In the method of the present invention, there is no complicated equipment connection and numerous step requirements, and the control equipment only needs one source meter. It has low technical difficulty, simple operation and better scalability.

[0014] The method of the present invention can accurately and effectively regulate the distribution of oxygen vacancies in Ga2O3, improve device performance, and effectively solve the problem that the responsivity and response recovery speed in the current Ga2O3 photodetector have a mutually restrictive and contradictory relationship.

[0015] The present invention uses ionic liquid as the gate material, which has a strong charge control capability. The field effect structure of the traditional gate material has a weak ability to control the carrier (<10 13 cm -2 ), it is difficult to correlate the carrier concentration of electron oxides (~10 14 cm -2 ) can be effectively regulated. In the ionic liquid structure of the present invention, the potential mainly falls on the double electric layer of the liquid / solid interface with a thickness of about 1 nm, and the corresponding carrier concentration can be higher than 10 14 -10 15 cm -2 , which can realize the regulation of the photoelectric properties of devices made of various materials including Ga2O3. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

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

[0020] Figure 5 It is a time-current (IT) curve diagram of the device on the Ga2O3 thin film before and after regulation in Example 3 of the present invention. DETAILED DESCRIPTION

[0021] The present invention is further described and illustrated below in conjunction with specific embodiments. The embodiments are merely exemplary of the present disclosure and do not define the scope of limitation. The technical features of each embodiment of the present invention may be combined accordingly without conflicting with each other.

[0022] In order to further illustrate the technical means of the present invention, the specific implementation steps and details of the method of the present invention are described in detail.

[0023] The present invention provides a method for regulating oxygen vacancies in a Ga2O3 film, which comprises the following steps in sequence: (1) preparing a Ga2O3 film and a device, (2) dripping an ionic liquid, and (3) applying a vertical electric field for regulation.

[0024] like Figure 1 As shown, in one embodiment of the present invention, step (1) includes: preparing a Ga2O3 film on the upper surface of a SiO2 / Si substrate; using a silicon wafer knife to scrape off the SiO2 layer on the bottom surface of the SiO2 / Si substrate, and connecting the exposed Si portion to a PCB board through liquid metal InGa as a bottom gate electrode; fixing the PCB board on a probe workbench with insulating tape; the probe workbench of this embodiment is a four-probe workbench, in which a source probe and a drain probe provide a source-drain voltage V SD , the top gate probe and the 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 film to prepare a gold electrode.

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

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

[0027] 1.1) Spin-coat photoresist on Ga2O3 film;

[0028] 1.2) Covering the photoresist with an interdigitated electrode photolithography mask and exposing it;

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

[0030] 1.4) Use a thermal evaporation coating machine to prepare gold electrodes, set the coating pressure to 1pa, the evaporation current to 40-50A, sputter gold electrode channels according to the development traces to prepare gold electrodes, and the thickness of the gold electrodes is 50-100nm; after the electrode preparation is completed, remove the glue and blow dry.

[0031] In one embodiment of the present invention, step (2) comprises: dripping an organic cationic salt ionic liquid onto the main body of the Ga2O3 film to form a layer of ionic liquid film, the area of ​​the ionic liquid film being smaller than the area of ​​the main body of the Ga2O3 film and only covering the gold electrode channel portion.

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

[0033] In one embodiment of the present invention, step (3) includes: inserting the top gate probe of the probe workbench into the ionic liquid film without contacting the main body of the Ga2O3 film; applying 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, so that the migration of oxygen vacancies in the Ga2O3 film is completed. The present invention can be controlled by the source-drain voltage V SD And optical pulse test the performance of the device after regulation.

[0034] In a specific embodiment of the present invention, the voltage applied when the top gate probe is connected to the positive pole of the power supply and the bottom gate probe is connected to the negative pole 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 DC continuous voltage, which causes the oxygen vacancies in the Ga2O3 film to migrate under the action of the strong electric field generated by the ionic liquid, thereby regulating the sample performance.

[0036] Embodiment 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 a SiO2 / Si substrate by atomic layer deposition (ALD);

[0039] Then, a metal-semiconductor-metal (MSM) photodetector is constructed on the Ga2O3 film using photolithography and evaporation processes. The specific operation of this process is as follows: Figure 2As shown, first, spin-coat the Ga2O3 film with a KW-4A type coating machine at 1000rpm (6s), 5000rpm (20s), and pre-bake on a 90°C heating plate for 3 minutes to obtain a photoresist coating with uniform thickness; then, use a photoresist-coated sample to cover the interdigitated electrode photolithography mask for exposure (3s), and place the exposed sample in a developer for development (30s), and then blow dry to obtain the sample; finally, use a thermal evaporation coating machine to prepare the Au electrode, set the coating pressure to 1pa, the evaporation current to 45A, and the Au film thickness to 60nm. After the electrode is prepared, place the sample in acetone with 60W ultrasound for about 30s to remove the glue and blow dry with N2 gas;

[0040] Step (2) Adding ionic liquid: Add an organic cationic salt ionic liquid on the main body of the Ga2O3 film to form an ionic liquid film. The area of ​​the ionic liquid film is smaller than the area of ​​the main body of the Ga2O3 film and only covers the gold electrode channel portion on the Ga2O3 film. The ionic liquid is a salt that is liquid at room temperature or close to room temperature and is completely composed of organic cations and inorganic or organic anions. The ionic concentration of the ionic liquid in the above step (2) is 97%, and the ionic liquid is C8H 11 F6N3O4S2, the thickness of the ionic liquid membrane is 2 mm.

[0041] Step (3) vertical electric field control: insert the probe of the probe workbench into the ionic liquid membrane without contacting the main body of the Ga2O3 film; connect the negative terminal of the source meter to the bottom electrode, and connect 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 to migrate oxygen vacancies in the Ga2O3 film to complete the performance control. The voltage application process must not damage the main body of the Ga2O3 film; the applied voltage is a DC continuous voltage, and the duration is 1 minute.

[0042] test:

[0043] (1) The photoelectrochemical performance of the Ga2O3 film before and after treatment was tested. The time-current (IT) curve obtained at a source-drain voltage of 2V is shown in the figure below. Figure 3 As shown, the performance of the samples is good before and after treatment, and the light and dark currents of the devices are reduced after regulation.

[0044] Embodiment 2:

[0045] The difference between this embodiment and implementation 1 is that the DC voltage value of the vertical electric field regulation process in step (3) is -5V; the photoelectrochemical performance of the Ga2O3 film before and after treatment is tested, and the time-current (IT) curve obtained at a source-drain voltage of 2V is as follows: Figure 4 As shown, the light and dark currents of the device are improved after regulation.

[0046] Embodiment 3:

[0047] The difference between this embodiment and embodiment 1 is that in the process of vertical electric field regulation in step (3), a +5V DC voltage is first applied for 1 minute, and then a -5V DC voltage is applied for 1 second. The photoelectrochemical performance of the Ga2O3 film before and after the treatment is tested. The time-current (IT) curve obtained at a source-drain voltage of 2V is as shown in FIG. Figure 4 As shown, after regulation, the photocurrent of the device increases and the dark current decreases, and the performance is significantly improved.

[0048] The oxygen vacancy control method of the Ga2O3 film of the above-mentioned embodiments 1 to 3 of the present invention has a simple Ga2O3 film structure and equipment, and the device preparation steps are simple. The present invention does not have complicated equipment connections and numerous step requirements, and the control equipment only needs a source meter, which has low technical difficulty, simple operation, and better promotion.

[0049] In the above-mentioned Ga2O3 thin film oxygen vacancy control method of embodiments 1 to 3 of the present invention, in the photoconductive Ga2O3 photodetector, the defect-related photoconductivity gain and continuous photoconductivity increase the responsivity and response recovery time respectively, so that the responsivity and response recovery speed have a mutually restrictive and contradictory relationship. It can be seen that accurately controlling the distribution of oxygen vacancies in Ga2O3 is the key to improving device performance. The field effect structure of traditional gate materials has weak carrier control ability and is difficult to control the carrier concentration (~10) of the associated electron oxide. 14 cm -2 ) for effective regulation. Using ionic liquid as the regulating material, the potential in the ionic liquid gate structure mainly falls on the double electric layer with a thickness of about 1nm at the liquid / solid interface, and the corresponding carrier concentration can be higher than 10 14 -10 15 cm -2 , which can realize the regulation of the metal-insulator transition of various materials including transition metal oxides. In addition, the strong electric field at the interface between ionic liquids and transition metal oxides will induce the migration of oxygen ions, leading to changes in physical properties.

[0050] The oxygen vacancy control method of the Ga2O3 film of the above-mentioned embodiments 1 to 3 of the present invention is time-consuming and has high control efficiency. Compared with the method of controlling oxygen vacancies through the field effect structure of the traditional gate material, which has high equipment operation requirements and complicated steps, the equipment of the present invention is simple to operate, has fewer steps, is time-consuming, and has higher efficiency in controlling device performance.

[0051] The above-mentioned embodiments only express several implementation methods of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. For ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A method for regulating oxygen vacancies in Ga2O3 thin films based on vertical electric field regulation, characterized in that: The following steps are involved: Step 1): Prepare a Ga2O3 film on the upper surface of a SiO2 / Si substrate; scrape off the SiO2 layer on the bottom surface of the SiO2 / Si substrate, and connect the exposed Si portion to a PCB board as a bottom gate electrode; fix the PCB board on a probe workbench, which is a four-probe workbench, wherein a source probe and a drain probe provide a source-drain voltage V SD , the top gate probe and the bottom gate probe provide the gate voltage V G ; Sputtering a gold electrode channel on the upper surface of the Ga2O3 film using photolithography and sputtering technology to prepare a gold electrode; Step 2): adding an organic cationic salt ionic liquid dropwise onto the Ga2O3 film to form an ionic liquid film; Step 3): insert the top gate probe of the probe workbench into the ionic liquid film without contacting the Ga2O3 film; a voltage source applies 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, so that the migration of oxygen vacancies in the Ga2O3 film is regulated.

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

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

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

5. The method according to claim 1, characterized in that In the step 1), a gold electrode channel is sputtered on the Ga2O3 film using photolithography and sputtering technology to prepare a gold electrode, which includes the following sub-steps: 1.1) Spin-coat photoresist on Ga2O3 film; 1.2) Covering the photoresist with an interdigitated electrode photolithography mask and exposing it; 1.3) Place the exposed sample in a developer for development and then blow dry; 1.4) Use a thermal evaporation coating machine to prepare gold electrodes, set the coating pressure to 1pa, the evaporation current to 40-50A, sputter gold electrode channels according to the development traces to prepare gold electrodes, and the thickness of the gold electrodes is 50-100nm; after the electrode preparation is completed, remove the glue and blow dry.

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

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

8. The method according to claim 1, characterized in that The voltage applied when the top gate probe is connected to the positive pole of the power supply and the bottom gate probe is connected to the negative pole 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.

9. The method according to claim 1, characterized in that: In step 3), the source-drain voltage V SD And optical pulse test the performance of the device after regulation.

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

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