Preparation method of porous gallium oxide based on pulse electrochemical corrosion

Abstract

This invention belongs to the field of electrocatalysis technology and discloses a method for preparing porous gallium oxide based on pulsed electrochemical corrosion. Using phosphoric acid solution as the electrolyte, and employing pulsed electrochemical corrosion at a pulse potential of 6-14 V for 20-90 min with a duty cycle of 30%-70%, porous gallium oxide was successfully prepared. This invention utilizes pulsed electrochemical corrosion under low-temperature conditions. During the pulse-on phase, it enhances the oxidation-dissolution reaction at the anodic interface and promotes the breaking of Ga-O bonds. During the pulse-off phase, the interfacial diffusion conditions are restored, and reaction products and locally accumulated ions are released in a timely manner. Through this periodic dissolution-recovery process, the surface passivation layer formed under continuous bias voltage is effectively overcome, promoting more uniform, continuous, and controllable local dissolution on the gallium oxide surface. Furthermore, through synergistic regulation with electrical parameters, a uniformly distributed and size-tunable porous structure is directly formed on a β-Ga2O3 substrate.

Description

Technical Field

[0001] This invention relates to the field of electrocatalysis technology, specifically to a method for preparing porous gallium oxide based on pulsed electrochemical corrosion. Background Technology

[0002] Gallium oxide (Ga₂O₃) is an inorganic compound. β-Ga₂O₃ is the most stable oxide form of gallium oxide, appearing as a white crystalline powder and widely used in semiconductor materials. As a fourth-generation wide-bandgap semiconductor material, β-Ga₂O₃, with its ultra-wide bandgap of approximately 4.9 eV, extremely high theoretical breakdown field strength, and excellent chemical and thermal stability, is widely considered a potential key material for high-voltage power electronic devices and ultraviolet detectors. Compared to materials such as Si, SiC, and GaN, gallium oxide's larger bandgap means it can withstand higher electric fields, which helps to realize smaller, higher-power-density devices. This is of great significance for fields such as new energy vehicles, high-voltage inverters, and power electronics.

[0003] Gallium oxide can grow large-size single wafers through low-cost processes such as the melting method, making mass production and industrialization of devices more cost-effective and feasible, and providing the industry with the possibility of breaking through the performance bottlenecks of traditional materials.

[0004] Porous structures are a class of functional structures in semiconductor materials, characterized by highly tunable porosity and large specific surface area. In the study of porous silicon, the porous layers formed by controlling electrochemical etching conditions allow for precise control of pore size, pore density, and pore morphology. These structures significantly alter the optical, electrical, and surface chemical properties of the material, thereby expanding its application potential in multiple fields such as optoelectronic devices, sensors, energy storage, and MEMS. Research shows that the high specific surface area and hierarchical pore structure of porous silicon enable it to exhibit excellent performance in gas sensing, dielectric modulation, and optical manipulation. These characteristics make porous silicon a typical example of porous semiconductor applications.

[0005] Similarly, the porosity of III-V semiconductors such as porous indium phosphide (InP) has also been achieved through methods such as etching, and its advantages are gradually becoming apparent in optoelectronic interconnects, through-hole structures, and sensing applications. These studies demonstrate that introducing porous structures into semiconductor materials can significantly enhance the functionality of the materials through geometric and interface effects, providing more freedom for improving device performance.

[0006] Although porous structures have been systematically studied in traditional and compound semiconductors such as silicon and indium phosphide, research on the porosity of gallium oxide (GaO) remains very limited. Current research on GaO mainly focuses on thin film deposition, crystal growth, doping control, and device structure optimization, while studies on the systematic fabrication and application performance of porous GaO structures are relatively scarce. Existing research occasionally involves achieving porous GaO systems derived from other materials through epitaxy or heterostructures. For example, patent CN113053730A discloses a porous GaO epitaxial layer and its preparation method, including: performing a low-temperature solution pre-oxidation treatment on the prepared porous GaN epitaxial layer for a first predetermined time; heating the pre-oxidized porous GaN epitaxial layer to a predetermined temperature; maintaining the predetermined temperature and oxidizing the heated porous GaN epitaxial layer under a high-oxygen gas atmosphere and a predetermined pressure for a second predetermined time to obtain the porous GaO epitaxial layer. However, such research is mostly derived from heterojunction device structures and has not formed a mature system for the bulk fabrication and performance research of porous GaO materials.

[0007] Furthermore, traditional wet etching methods suffer from slow etching rates due to the strength of the Ga-O bonds in gallium oxide (GaO), and are easily affected by factors such as solution type, temperature, and etching conditions, leading to difficulties in the preparation of porous GaO structures. The lack of porous structures in GaO is partly due to the difficulty in forming stable pores on its surface using traditional methods, especially in wet etching where the low etching rate and significant lateral corrosion negatively impact the uniformity and controllability of the pore structure. Moreover, due to the crystal structure and high chemical stability of GaO, traditional wet etching cannot effectively control pore morphology at lower temperatures, and may introduce new defects during the process, further exacerbating the difficulty of preparing porous GaO structures. Therefore, developing a new technique for efficiently preparing porous GaO structures at lower temperatures is particularly important. Summary of the Invention

[0008] This invention addresses the problems of slow corrosion rate, severe lateral corrosion, and poor mask selectivity in traditional porous structure fabrication methods, which limit the precise fabrication of porous structures. It provides a method for fabricating porous gallium oxide based on pulsed electrochemical corrosion. This method directly fabricates porous structures on β-Ga2O3 substrates through electrochemical corrosion at low temperatures. By controlling the electrical parameters during the electrochemical corrosion process, the porosity, pore size, and pore depth of the porous structure on the gallium oxide surface can be precisely controlled, meeting the specific requirements of various devices for material porosity and morphology. Furthermore, it avoids damage caused by high temperatures, improves corrosion efficiency, and reduces lateral corrosion.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing porous gallium oxide based on pulsed electrochemical etching, comprising: Porous gallium oxide was prepared on a gallium oxide substrate by pulsed electrochemical etching using phosphoric acid solution as electrolyte. The conditions for pulsed electrochemical corrosion are: corrosion at a pulse potential of 6-14 V for 20-90 min, with a duty cycle of 30%-70%.

[0010] This invention is based on a pulsed electrochemical corrosion method. Gallium oxide material is used as the anode, contacting the electrolyte and applying a pulsed bias voltage. The electric field drives the migration of electrons and ions at the interface, inducing a surface electrochemical reaction at the semiconductor / electrolyte interface. On the anode side, an oxidation-dissolution reaction occurs on the gallium oxide surface, where Ga-O bonds gradually break with the participation of holes, allowing surface Ga elements to enter the solution, thus causing localized dissolution of the material. On the cathode side, a hydrogen evolution reaction mainly occurs, where hydrogen ions in the electrolyte gain electrons to generate hydrogen gas. The anodic oxidation-dissolution and cathode hydrogen evolution reactions together constitute a complete electrochemical corrosion process, where the localized dissolution of the anode surface is the basis for the formation of the porous structure. The reaction equation is as follows: 2H + +2e - →H2↑ (cathode) 2Ga₂O₃ + 12H₂O + →4Ga 3+ +3O2↑ (Anode reaction 1) Ga 3+ +PO4 3- →GaPO4↓ (Anodic reaction 2) In the above process, the dissolution rate of gallium oxide surface is jointly affected by factors such as current density, voltage, pulse parameters, and electrolyte composition. Due to the high chemical stability of gallium oxide, a passivation layer easily forms on the surface when a DC voltage is continuously applied, thus hindering subsequent charge transfer and further dissolution of the material, resulting in decreased corrosion efficiency and poor structural uniformity. The introduction of pulse voltage can effectively alleviate the above problems: during the pulse conduction phase, the higher instantaneous electric field intensity is conducive to enhancing the oxidation-dissolution reaction at the anode interface, promoting Ga-O bond breaking and material removal; during the pulse turn-off phase, the interface diffusion conditions are restored, and reaction products and locally accumulated ions are released in time, thereby weakening the surface passivation effect. Through this periodic dissolution-recovery process, the surface passivation layer formed under continuous bias can be effectively broken through, promoting more uniform, continuous, and controllable local dissolution of gallium oxide surface, ultimately forming a uniformly distributed, size-tunable porous structure.

[0011] Furthermore, by selecting pulsed electrochemical etching conditions within the aforementioned range, a suitable etching rate can be maintained to obtain a continuous porous structure, which is less likely to lead to uncontrolled pore size distribution or uneven surface morphology. It also maintains a balance between continuous dissolution and local passivation on the gallium oxide substrate surface, forming a porous gallium oxide with a complete and uniform surface and no void merging.

[0012] Preferably, the mass fraction of phosphoric acid in the electrolyte is 30%-85%.

[0013] More preferably, the mass fraction of phosphoric acid in the electrolyte is 85%.

[0014] Preferably, in the pulsed electrochemical corrosion, a gallium oxide substrate with (100) orientation is used as the anode, one side of the gallium oxide substrate is electrically connected to a conductive platinum plate, the conductive platinum plate is used to achieve conduction, and the cathode is a platinum mesh.

[0015] First, the (100) crystal plane has good chemical stability and is easy to process, making it an ideal interface for large-scale crystal size expansion. By tightly bonding the (100) crystal plane-oriented gallium oxide substrate to the platinum plate, the platinum plate is used as the back conductive electrode to achieve the introduction of external bias voltage.

[0016] Preferably, the temperature of the pulsed electrochemical corrosion is controlled between 20℃ and 70℃.

[0017] On the other hand, the present invention also provides porous gallium oxide prepared by the aforementioned method for preparing porous gallium oxide based on pulsed electrochemical corrosion.

[0018] Preferably, the porous gallium oxide has pores that are distributed in a rectangular shape, with the long side arranged along the

[010] crystal direction and the wide side arranged along the

[001] crystal direction.

[0019] More preferably, the long side ranges from 1 to 10 μm, and the wide side ranges from 0.1 to 3 μm.

[0020] Preferably, the porous gallium oxide has a porosity of 4%-50% and a pore depth of 10-30 nm.

[0021] Furthermore, the present invention also provides the application of the aforementioned porous gallium oxide in the fabrication of electronic devices and detectors.

[0022] Compared with the prior art, the present invention has the following beneficial effects: (1) In this invention, a porous structure of gallium oxide was directly prepared on a β-Ga2O3 substrate; (2) Based on pulsed electrochemical corrosion, by controlling the voltage and pulse time during the electrochemical corrosion process, the porosity, pore size, and pore depth of the porous structure on the gallium oxide surface can be precisely controlled. This precise control of electrical parameters not only improves the preparation accuracy of porous gallium oxide, but also provides the required pore structure for different types of high-performance devices (such as optoelectronic devices, sensors, and energy storage devices), meeting the specific requirements of various devices for material porosity and morphology; (3) The process conditions are mild (room temperature to medium and low temperature, low voltage is sufficient) and there is no need for high concentration of strong corrosive chemicals. Therefore, it is more compatible with existing semiconductor processing procedures and has better environmental friendliness and safety. Attached Figure Description

[0023] Figure 1 The results are obtained by differential interference microscopy of porous gallium oxide obtained in Example 1.

[0024] Figure 2 The results are from scanning electron microscopy of porous gallium oxide obtained in Example 1.

[0025] Figure 3 The results are obtained by high-magnification scanning electron microscopy of porous gallium oxide obtained in Example 1.

[0026] Figure 4 The results are obtained from atomic force microscopy of porous gallium oxide obtained in Example 1.

[0027] Figure 5 The results are obtained by scanning electron microscopy of porous gallium oxide from Example 2.

[0028] Figure 6 The results are obtained from atomic force microscopy of porous gallium oxide in Example 2.

[0029] Figure 7 The results are obtained by scanning electron microscopy of porous gallium oxide obtained in Example 3.

[0030] Figure 8 The results are obtained from optical microscopy of the gallium oxide wafer obtained in Comparative Example 1.

[0031] Figure 9 The results are obtained by scanning electron microscopy of the gallium oxide wafer obtained in Comparative Example 2.

[0032] Figure 10 The results are obtained by optical microscopy of the gallium oxide wafer obtained in Comparative Example 3.

[0033] Figure 11 The results are obtained by optical microscopy of the gallium oxide wafer obtained in Comparative Example 4. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Modifications or equivalent substitutions made by those skilled in the art based on their understanding of the technical solutions of this invention, without departing from the spirit and scope of the invention, should all be covered within the protection scope of this invention.

[0035] All raw materials used in the following specific implementation methods were purchased from the market.

[0036] Example 1 An 85% phosphoric acid solution was used as both the etching solution and the conductor. A (100) oriented gallium oxide substrate was tightly bonded to an anode platinum plate. The anode platinum plate served as the back conductive electrode to introduce the applied bias voltage. A 1 cm × 1 cm platinum mesh was used as the cathode. Pulsed electrochemical etching was performed using an electrochemical workstation with a pulse voltage of 10 V and a conduction time T. on The off time is 1 second, and the off time is T. off The etching time was 1 s, the duty cycle was 50%, the etching time was 60 min, and the reaction temperature was 25℃, resulting in an etched gallium oxide wafer. The etched gallium oxide wafer was removed and cleaned in deionized water, followed by ultrasonic cleaning with acetone, isopropanol and anhydrous ethanol in sequence. After cleaning, it was dried with an air gun and stored in a clean adsorption box.

[0037] like Figure 1 As shown, under a 200x differential interference microscope, the holes in the etched gallium oxide wafer are generally distributed in a rectangular pattern. The long sides are all arranged along the

[010] crystal direction, about 5 μm, and the wide sides are arranged along the

[001] crystal direction, about 1.5 μm. The holes are randomly distributed on the surface, indicating the successful preparation of porous gallium oxide.

[0038] Scanning electron microscopy can provide clear morphological features of the etched gallium oxide wafer surface. For example... Figure 2 As shown, the surface is generally smooth, without any obvious passivation layer or uneven corrosion. The image reveals a distinct monopore structure, with pores of uniform size and even distribution. Each monopore contains multiple nanoscale pores.

[0039] Furthermore, such as Figure 3As shown, clear morphological features of the interior of individual pores can be obtained under a high-magnification scanning electron microscope. These porous structures are composed of many nanoscale pores. The surface porosity of the samples was obtained by processing the scanning electron microscope images using ImageJ software. The processing included: cropping representative surface morphology images to remove scale bars and irrelevant background areas; converting the images to grayscale; using a threshold segmentation method to binarize and identify the porous and non-porous parts; and calculating the ratio of the porous area to the total analyzed area, which was defined as the surface porosity. To reduce errors caused by local regional differences, multi-region statistics were performed on each sample and the average value was taken. The porosity of Example 1 was 31.2%.

[0040] like Figure 4 As shown, the sample surface was tested using an atomic force microscope, and the height map was corrected for plane and cross-sectional analysis using NanoScope Analysis software. By statistically analyzing the average height difference between the concave and non-concave areas on the surface, the average depth was found to be approximately 13 nm.

[0041] Example 2 The process of Example 2 is the same as that of Example 1, except that the conduction time T is different. on The turn-off time is 1.4 s, and the turn-off time T is 1.4 s. off The duration is 0.6s, and the duty cycle is 70%.

[0042] like Figure 5 As shown, even with an increased duty cycle, a relatively continuous porous structure can still be formed on the surface. The porosity is significantly increased to 47.6%, with local pore walls becoming thinner, local corrosion channels becoming more interconnected, and the clarity of pore boundaries decreasing.

[0043] Furthermore, such as Figure 6 As shown, analysis using NanoScope Analysis software revealed an average pore depth of approximately 30 nm. Compared to Example 1 with a duty cycle of 50%, the pore depth is significantly increased, indicating that the corrosion of the gallium oxide surface is further enhanced with an increased duty cycle, and the pores expand more significantly along the depth direction.

[0044] Example 3 The process of Example 3 is the same as that of Example 1, except that the corrosion time is 20 min.

[0045] like Figure 7 As shown, compared with longer corrosion time, shorter corrosion time results in a more preliminary pore morphology, with a porosity of 4.9%.

[0046] Comparative Example 1 The process of Comparative Example 1 is the same as that of Example 1, except that: the external electric field is 10 V, no pulse is set, the corrosion time is 60 min, and the reaction temperature is 25℃.

[0047] like Figure 8 As shown, gallium oxide was etched using a constant potential, resulting only in surface passivation. The electrochemical reaction quickly stopped, and the surface appeared smooth and clean under an optical microscope.

[0048] Comparative Example 2 The process of Comparative Example 2 is the same as that of Example 1, except that the pulse voltage is 15 V.

[0049] like Figure 9 As shown, under higher voltage conditions, the corrosion rate of gallium oxide surface accelerates significantly, leading to the merging of adjacent pores during expansion and exhibiting a clear pore size fusion phenomenon. Scanning electron microscopy results indicate that the independence and order of the porous structure are disrupted, and the overall morphology tends to become disordered. Therefore, strict control of electrical parameters is required to prepare porous gallium oxide.

[0050] Comparative Example 3 The process of Comparative Example 3 is the same as that of Example 1, except that the pulse voltage is 20 V and the reaction temperature is 80 °C.

[0051] like Figure 10 As shown, increasing the pulse voltage to 20 V and the corrosion temperature to 80 °C significantly intensifies the corrosion of gallium oxide surfaces, making it difficult to form clearly defined and uniformly distributed independent porous structures. The figure reveals a striped and sheet-like corrosion morphology on the surface, with significant fusion of local pores. This indicates that under the combined effects of high voltage and high temperature, the material surface dissolves too quickly, disrupting the order and controllability of the porous structure.

[0052] Comparative Example 4 The process of Comparative Example 4 is the same as that of Example 1, except that the pulse voltage is 5 V.

[0053] like Figure 11 As shown, reducing the applied external electric field to 5 V did not reach the threshold voltage required by the system, so the reaction did not proceed, and the surface was smooth and clean under an optical microscope.

Claims

1. A method for preparing porous gallium oxide based on pulsed electrochemical corrosion, characterized in that, include: Porous gallium oxide was prepared on a gallium oxide substrate by pulsed electrochemical etching using phosphoric acid solution as electrolyte. The conditions for pulsed electrochemical corrosion are: corrosion at a pulse potential of 6-14 V for 20-90 min, with a duty cycle of 30%-70%.

2. The method for preparing porous gallium oxide based on pulsed electrochemical corrosion according to claim 1, characterized in that, The mass fraction of phosphoric acid in the electrolyte is 30%-85%.

3. The method for preparing porous gallium oxide based on pulsed electrochemical corrosion according to claim 1, characterized in that, In pulsed electrochemical corrosion, a gallium oxide substrate with (100) orientation is used as the anode, and one side of the gallium oxide substrate is electrically connected to a conductive platinum plate, which is used to achieve conduction. The cathode is a platinum mesh.

4. The method for preparing porous gallium oxide based on pulsed electrochemical corrosion according to claim 1, characterized in that, The temperature for pulsed electrochemical corrosion is controlled between 20℃ and 70℃.

5. A porous gallium oxide prepared by a method for preparing porous gallium oxide based on pulsed electrochemical corrosion according to any one of claims 1-4.

6. The porous gallium oxide according to claim 5, characterized in that, The porous gallium oxide has pores that are distributed in a rectangular shape, with the long side arranged along the [010] crystal direction and the wide side arranged along the [001] crystal direction.

7. The porous gallium oxide according to claim 6, characterized in that, The long side ranges from 1 to 10 μm, and the wide side ranges from 0.1 to 3 μm.

8. The porous gallium oxide according to claim 5, characterized in that, Porous gallium oxide has a porosity of 4%-50% and a pore depth of 10-30 nm.

9. The application of porous gallium oxide according to any one of claims 5-8 in the fabrication of electronic devices and detectors.

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