An ohmic contact composite electrode for a gallium oxide device and a method of manufacturing the same

Abstract

The application discloses an ohmic contact composite electrode for a gallium oxide device and a preparation method thereof, realizes the composite electrode forming ohmic contact with a gallium oxide material, and adopts a combination form of a low-resistance composite intermediate layer-metal electrode for the composite electrode structure forming ohmic contact with the gallium oxide material, and the whole is sequentially formed by layering and assembling four parts of a gallium oxide material, a low-resistance doped gallium oxide intermediate layer, a low-resistance oxide semiconductor intermediate layer and a metal electrode; wherein the gallium oxide material can include single crystal, polycrystal and amorphous gallium oxide. The composite electrode designed in the application introduces a low-resistance composite intermediate layer, solves the problem that the traditional multilayer metal laminated electrode is easy to cause interface reaction in the alloying process, the novel composite electrode reduces the influence of the interface, improves the contact characteristics of the gallium oxide material electrode, realizes more stable ohmic contact for the gallium oxide material, makes the electrical performance of the gallium oxide device more reliable, and has a wide application prospect in the field of gallium oxide power electronic devices.

Description

Technical Field

[0001] This invention relates to a method for preparing a composite electrode that achieves ohmic contact with gallium oxide (Ga2O3) material, belonging to the field of semiconductor material manufacturing technology. Background Technology

[0002] Gallium oxide (Ga2O3) is a novel direct bandgap semiconductor material with an ultra-wide bandgap of approximately 4.9 eV. It exhibits high transmittance in the visible and deep ultraviolet regions, with an average transmittance exceeding 80%, making it suitable for applications such as solar-blind ultraviolet photodetectors and transparent conductive films. Furthermore, its breakdown voltage is 8 MV / cm, more than 20 times that of Si and more than twice that of SiC and GaN. It also possesses a large Barley figure of merit, almost 10 times that of SiC. This means that Ga2O3-based power devices have lower conduction losses and higher power conversion efficiency, thus showing great promise for applications in high-power devices.

[0003] In practical applications of semiconductor devices, the contact resistance between the metal and the semiconductor directly affects the output power, noise frequency characteristics, and thermal stability of the semiconductor device. Therefore, how to fabricate ohmic contacts with low specific contact resistance and high stability has become a key aspect of Ga2O3 device fabrication technology. For high-resistivity gallium oxide materials, obtaining good ohmic contacts is difficult. Currently, Ti / Au multi-metal stacked electrodes remain the most commonly used electrodes for achieving ohmic contacts in gallium oxide materials. The mechanism involves the bonding of the Ti layer with oxygen on the Ga2O3 surface, resulting in a high concentration of oxygen vacancies on the Ga2O3 surface, acting as donors. This effectively reduces the potential barrier width between Ga2O3 and the electrode, increasing the probability of carrier tunneling and promoting better ohmic contact. However, such multi-metal stacked electrodes are prone to adverse effects during alloying, such as surface structure degradation and surface roughening due to strong interfacial reactions, affecting the electrical performance and reliability of the device. To address these issues and improve the electrode contact characteristics of Ga2O3 materials, we propose a novel composite electrode structure that promotes good ohmic contact between Ga2O3 and the electrode by introducing a low-resistance semiconductor interlayer. Summary of the Invention

[0004] To address the problems of existing technologies, the present invention aims to overcome the shortcomings of existing technologies and provide an ohmic contact composite electrode for gallium oxide devices and its preparation method. This composite electrode structure can form an ohmic contact with gallium oxide materials, allowing it to exhibit superior performance in electronic device applications. The present invention employs a novel composite electrode structure, introducing a low-resistance semiconductor interlayer to promote the formation of a good ohmic contact between Ga2O3 and the electrode.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] An ohmic contact composite electrode for gallium oxide devices employs a combination of a low-resistivity composite interlayer and a metal electrode to form an ohmic contact with gallium oxide material. The composite electrode structure is assembled by stacking four parts sequentially: gallium oxide material, a low-resistivity doped gallium oxide interlayer, a low-resistivity oxide semiconductor interlayer, and a metal electrode. The gallium oxide material includes single-crystal, polycrystalline, and amorphous gallium oxide. The composite electrode incorporates a low-resistivity composite interlayer composed of a low-resistivity doped gallium oxide thin film and a low-resistivity oxide semiconductor thin film, reducing the influence of the interface and achieving a better and more stable ohmic contact with the gallium oxide material, thus making the electrical performance of the gallium oxide device more reliable.

[0007] The aforementioned low-resistivity doped gallium oxide intermediate layer is preferably doped with any one of Ta or V.

[0008] Preferably, the resistivity is not higher than 2 Ω·cm and the carrier concentration is not lower than 10. 17 cm -3 A gallium oxide-doped thin film is used as the intermediate layer.

[0009] The preferred method is to grow the gallium oxide intermediate layer by magnetron sputtering. The purity of the target material is calculated based on the concentration ratio of impurities contained in the target material. The preferred target material has a gallium oxide purity of 99.99% and a doping element content of no more than 10 at.%.

[0010] Preferably, the resistivity is not higher than 0.02 Ω·cm and the carrier concentration is not lower than 10. 19 cm -3 The oxide semiconductor thin film is used as the low-resistivity oxide semiconductor intermediate layer, and ZnO (BGZO) thin film doped with B and Ga elements is further preferred as the low-resistivity oxide semiconductor intermediate layer.

[0011] The low-resistivity oxide semiconductor intermediate layer is preferably grown by magnetron sputtering. The purity of the target material is calculated based on the concentration ratio of impurities contained in the target material. Oxide semiconductor materials with a purity of not less than 99.99% are preferred as the target material.

[0012] The purity of a metal material is calculated by using the concentration ratio of impurities in the material. High-purity metals with a purity of not less than 99% are preferred as the target material, and metal electrodes are deposited by vacuum evaporation or electron beam evaporation.

[0013] Preferably, the metal target material used to prepare the above-mentioned metal electrode is at least one of gold, titanium, aluminum or chromium.

[0014] Preferably, the thickness of the above-mentioned doped gallium oxide intermediate layer is 1 to 100 nm; preferably, the thickness of the above-mentioned low-resistivity oxide semiconductor intermediate layer is 1 to 200 nm; and preferably, the thickness of the above-mentioned metal electrode is 1 to 200 nm.

[0015] A method for preparing an ohmic contact composite electrode for gallium oxide devices according to the present invention includes the following steps:

[0016] (1) Fabrication of low-resistivity doped gallium oxide interlayer

[0017] A gallium oxide doped intermediate layer film was grown on pure gallium oxide using magnetron sputtering. A gallium oxide target containing doped elements was selected, with a gallium oxide purity ≥ 99.99%; the base vacuum of the sputtering chamber was ≤ 10 °C. -6 Torr, substrate temperature 100–900°C, high-purity argon gas is introduced into the cavity, and the sputtering pressure is controlled at 10. -3 ~10 -2 Torr sputtering power is 10-200W, the tray is rotatable, the growth thickness is controlled from 1 to 100nm, after the preparation process is completed, the film is allowed to cool naturally to room temperature, and then it is taken out to obtain a low-resistivity doped gallium oxide intermediate layer.

[0018] (2) Fabrication of low-resistivity oxide semiconductor interlayer

[0019] A low-resistivity oxide semiconductor interlayer is grown on the gallium oxide interlayer prepared in step (1); a BGZO thin film is selected as the interlayer, and a ZnO target doped with B and Ga elements is selected, wherein the ZnO purity is 99.99%, and it is doped with 0.1-1 wt.% B2O3 and 1-1.9 wt.% Ga2O3; the base vacuum of the sputtering cavity is ≤10 -6 Torr fills the cavity with high-purity argon gas, controlling the sputtering pressure to 10. -3 ~10 -2 Torr sputtering power is 10-200W, the tray is rotatable, the growth thickness is controlled to be 1-200nm, and after the fabrication process is completed, the low-resistivity oxide semiconductor intermediate layer is obtained by taking it out.

[0020] (3) Preparation of metal electrodes

[0021] A metal electrode is grown on the low-resistivity composite intermediate layer prepared in steps (1) and (2). The purity of the metal material is calculated by using the concentration ratio of impurities contained in the material as the target material. A high-purity metal with a purity of 99 to 99.9999% is selected. An electron beam evaporation deposition method is used to grow a metal electrode with a thickness of 1 to 200 nm on the low-resistivity intermediate layer. The electrode is then removed from the cavity to obtain an ohmic contact composite electrode for gallium oxide devices.

[0022] The preferred growth temperature is room temperature. This invention employs a physical preparation process, using radio frequency magnetron sputtering and electron beam evaporation deposition, which is simpler to operate, lower in cost, allows for large-area preparation, and has high feasibility for batch growth compared to other growth processes.

[0023] As a preferred embodiment of the present invention, in step (1), the base vacuum of the sputtering cavity is 10. -7 Torr, substrate temperature 700℃, high-purity argon gas is introduced into the cavity, and the sputtering pressure is controlled at 6×10⁻⁶. -3 The sputtering power was 150W, the tray rotation speed was controlled at 5rad / min, and the thickness was controlled at 50nm. After the fabrication process was completed, the film was allowed to cool naturally to room temperature, and the gallium oxide intermediate layer was obtained by taking it out.

[0024] As a preferred embodiment of the present invention, in step (2), the base vacuum of the sputtering cavity is 10. -7 Torr fills the cavity with high-purity argon gas, controlling the sputtering pressure to 6 × 10⁻⁶. -3 The Torr sputtering power is 150W, the tray rotation speed is controlled at 5rad / min, and the thickness is controlled at 100nm. After the fabrication process is completed, the low-resistivity oxide semiconductor intermediate layer is obtained.

[0025] Compared with the prior art, the present invention has the following prominent substantive features and significant advantages:

[0026] 1. The composite electrode designed in this invention is not limited to the crystal form of gallium oxide and can be used for single crystal, polycrystalline, and amorphous gallium oxide;

[0027] 2. This invention addresses the problem of interfacial reactions easily caused during the alloying process of traditional multilayer metal stacked electrodes by introducing a low-resistivity composite intermediate layer technology. The novel composite electrode reduces the influence of the interface, achieves a more stable ohmic contact with gallium oxide material, and makes the electrical performance of gallium oxide devices more reliable.

[0028] 3. This invention employs a physical preparation process, using radio frequency magnetron sputtering and electron beam evaporation deposition methods. Compared with other growth processes, it is simpler to operate, lower in cost, can be prepared on a large area, and has high feasibility for batch growth. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of an ohmic contact composite electrode structure for gallium oxide devices. Detailed Implementation

[0030] The above solution will be further described below with reference to specific embodiments. The preferred embodiments of the present invention are described in detail below:

[0031] Example 1:

[0032] In this embodiment, see Figure 1A schematic diagram of an ohmic contact composite electrode structure for gallium oxide devices is shown. The composite electrode structure forming the ohmic contact with the gallium oxide material adopts a combination of a low-resistivity composite interlayer and a metal electrode. The entire structure is assembled by stacking four parts sequentially: β-Ga₂O₃ material, a low-resistivity doped gallium oxide interlayer, a low-resistivity oxide semiconductor interlayer, and a metal electrode. First, a low-resistivity doped gallium oxide interlayer with Ta as the dopant element is grown on the β-Ga₂O₃. Then, a low-resistivity BGZO thin film interlayer is grown on the doped gallium oxide interlayer using magnetron sputtering. Finally, a metal electrode is grown on the low-resistivity composite interlayer using electron beam evaporation. High-purity Au with a purity of 99.999% is selected as the material for electron beam evaporation, based on the proportion of impurities in the metal as the calculation method for metal purity.

[0033] A method for fabricating an ohmic contact composite electrode for gallium oxide devices includes the following steps:

[0034] (1) Material cleaning and pretreatment:

[0035] β-Ga2O3 material with a size of 20mm×20mm was selected and ultrasonicated for 6 minutes in deionized water, acetone, anhydrous ethanol and deionized water respectively. After being dried with high-purity nitrogen, a clean and dry β-Ga2O3 material was obtained, which improved the surface state of the material. Then the cleaned β-Ga2O3 material was quickly transferred into a vacuum chamber.

[0036] (2) Fabrication of low-resistivity doped gallium oxide interlayer

[0037] The cleaned β-Ga2O3 material from step (1) is placed into the vacuum chamber. A gallium oxide target doped with Ta is selected, with a gallium oxide purity of 99.99% and 10 at.% Ta2O5 doping. The base vacuum of the chamber is 10. -7 Torr is activated, the tray rotates at a rate of 5 rad / min, the substrate temperature is raised to 700℃ (heating rate: 10℃ / min), high-purity argon gas is introduced into the cavity, and the sputtering pressure is controlled at 6 × 10⁻⁶. -3 The sputtering power was 150 W. After the fabrication process, the film was allowed to cool naturally to room temperature, and the resulting low-resistivity doped gallium oxide interlayer was obtained. The interlayer thickness was approximately 50 nm, the resistivity was approximately 0.9 Ω·cm, and the carrier concentration was approximately 2 × 10⁻⁶. 19 cm -3 .

[0038] (3) Fabrication of low-resistivity oxide semiconductor interlayer

[0039] A low-resistivity oxide semiconductor interlayer is grown on the gallium oxide interlayer prepared in step (2). A BGZO thin film is selected as this interlayer, and a ZnO target doped with B and Ga elements is chosen, wherein the ZnO purity is 99.99%, and it is doped with 0.2 wt.% B₂O₃ and 1.8 wt.% Ga₂O₃. The base vacuum of the sputtering cavity is 10... -7 Torr fills the cavity with high-purity argon gas, controlling the sputtering pressure to 6 × 10⁻⁶. -3 The sputtering power was 150W, and the tray rotation speed was controlled at 5 rad / min. After the fabrication process was completed, a low-resistivity oxide semiconductor interlayer was obtained. The interlayer thickness was approximately 100 nm, the resistivity was approximately 0.002 Ω·cm, and the carrier concentration was approximately 3 × 10⁻⁶. 20 cm -3 .

[0040] (4) Preparation of Au metal electrode

[0041] A 100 nm Au electrode layer was grown on the low-resistivity composite intermediate layer prepared in steps (2) and (3) using electron beam evaporation deposition. High-purity Au was used, and the metal purity was calculated as 99.999% based on the proportion of impurities in the metal. The electron beam voltage was 9.7 keV, the power was set to 39.6%, and the growth rate was controlled using a crystal oscillator. The growth rate of Au was... The growth temperature was room temperature. The electrode was then removed from the cavity to obtain a composite electrode for gallium oxide.

[0042] Example 2:

[0043] This embodiment is basically the same as Embodiment 1, except that:

[0044] In this embodiment, the gallium oxide device uses an ohmic contact composite electrode structure. The composite electrode structure that forms an ohmic contact with the gallium oxide material adopts a combination of a low-resistivity composite interlayer and a metal electrode. The entire structure is assembled by stacking four parts in sequence: β-Ga₂O₃ material, a low-resistivity doped gallium oxide interlayer, a low-resistivity oxide semiconductor interlayer, and a metal electrode. First, a low-resistivity doped gallium oxide interlayer with V as the dopant element is grown on the β-Ga₂O₃ using magnetron sputtering. Then, a low-resistivity BGZO thin film interlayer is grown on the doped gallium oxide interlayer using magnetron sputtering. Finally, a metal electrode is grown on the low-resistivity composite interlayer using electron beam evaporation. High-purity Au with a purity of 99.999% is selected as the material for electron beam evaporation, based on the proportion of impurity concentration in the metal as the calculation method for metal purity.

[0045] A method for fabricating an ohmic contact composite electrode for gallium oxide devices includes the following steps:

[0046] (1) Material cleaning and pretreatment:

[0047] β-Ga2O3 material with a size of 20mm×20mm was selected and ultrasonicated for 6 minutes in deionized water, acetone, anhydrous ethanol and deionized water respectively. After being dried with high-purity nitrogen, a clean and dry β-Ga2O3 material was obtained, which improved the surface state of the material. Then the cleaned β-Ga2O3 material was quickly transferred into a vacuum chamber.

[0048] (2) Fabrication of low-resistivity doped gallium oxide interlayer

[0049] The cleaned β-Ga2O3 material from step (1) is placed into the vacuum chamber. A gallium oxide target doped with V is selected, with a gallium oxide purity of 99.99% and 5 at.% V2O5 doping. The base vacuum of the chamber is 10. -7 Torr is activated, the tray rotates at a rate of 5 rad / min, the substrate temperature is raised to 700℃ (heating rate: 10℃ / min), high-purity argon gas is introduced into the cavity, and the sputtering pressure is controlled at 6 × 10⁻⁶. -3 The sputtering power was 150 W. After the fabrication process, the film was allowed to cool naturally to room temperature, and the resulting low-resistivity doped gallium oxide interlayer was obtained. The interlayer thickness was approximately 50 nm, the resistivity was approximately 1.2 Ω·cm, and the carrier concentration was approximately 9 × 10⁻⁶. 18 cm -3 .

[0050] (3) Fabrication of low-resistivity oxide semiconductor interlayer

[0051] A low-resistivity oxide semiconductor interlayer is grown on the gallium oxide interlayer prepared in step (2). A BGZO thin film is selected as this interlayer, and a ZnO target doped with B and Ga elements is chosen, wherein the ZnO purity is 99.99%, and it is doped with 0.2 wt.% B₂O₃ and 1.8 wt.% Ga₂O₃. The base vacuum of the sputtering cavity is 10... -7 Torr fills the cavity with high-purity argon gas, controlling the sputtering pressure to 6 × 10⁻⁶. -3 The sputtering power was 150W, and the tray rotation speed was controlled at 5 rad / min. After the fabrication process was completed, a low-resistivity oxide semiconductor interlayer was obtained. The interlayer thickness was approximately 100 nm, the resistivity was approximately 0.002 Ω·cm, and the carrier concentration was approximately 3 × 10⁻⁶. 20 cm -3 .

[0052] (4) Preparation of Au metal electrode

[0053] A 100 nm Au electrode layer was grown on the low-resistivity composite intermediate layer grown in steps (2) and (3) using electron beam evaporation deposition. High-purity Au was used, and the metal purity was calculated as 99.999% based on the proportion of impurities in the metal. The electron beam voltage was 9.7 keV, the power was set to 39.6%, and the growth rate was controlled using a crystal oscillator. The growth rate of Au was... The growth temperature was room temperature. The electrode was then removed from the cavity to obtain a composite electrode for gallium oxide.

[0054] Example 3:

[0055] This embodiment is basically the same as the previous embodiments, except that:

[0056] In this embodiment, the gallium oxide device uses an ohmic contact composite electrode structure. The composite electrode structure that forms an ohmic contact with the gallium oxide material adopts a combination of a low-resistivity composite interlayer and a metal electrode. The entire structure is assembled by stacking four parts in sequence: β-Ga₂O₃ material, a low-resistivity doped gallium oxide interlayer, a low-resistivity oxide semiconductor interlayer, and a metal electrode. First, a low-resistivity doped gallium oxide interlayer with Ta as the dopant element is grown on the β-Ga₂O₃. Then, a low-resistivity BGZO thin film interlayer is grown on the doped gallium oxide interlayer using magnetron sputtering. Finally, a metal electrode is grown on the low-resistivity composite interlayer using electron beam evaporation. High-purity Cr with a purity of 99.999% is selected as the material for electron beam evaporation, based on the proportion of impurity concentration in the metal as the calculation method for metal purity.

[0057] A method for fabricating an ohmic contact composite electrode for gallium oxide devices includes the following steps:

[0058] (1) Material cleaning and pretreatment:

[0059] β-Ga2O3 material with a size of 20mm×20mm was selected and ultrasonicated for 6 minutes in deionized water, acetone, anhydrous ethanol and deionized water respectively. After being dried with high-purity nitrogen, a clean and dry β-Ga2O3 material was obtained, which improved the surface state of the material. Then the cleaned β-Ga2O3 material was quickly transferred into a vacuum chamber.

[0060] (2) Fabrication of low-resistivity doped gallium oxide interlayer

[0061] The cleaned β-Ga2O3 material from step (1) is placed into the vacuum chamber. A gallium oxide target doped with Ta is selected, with a gallium oxide purity of 99.99% and 10 at.% Ta2O5 doping. The base vacuum of the chamber is 10. -7Torr is activated, the tray rotates at a rate of 5 rad / min, the substrate temperature is raised to 700℃ (heating rate: 10℃ / min), high-purity argon gas is introduced into the cavity, and the sputtering pressure is controlled at 6 × 10⁻⁶. -3 The sputtering power was 150 W. After the fabrication process, the film was allowed to cool naturally to room temperature, and the resulting low-resistivity doped gallium oxide interlayer was obtained. The interlayer thickness was approximately 50 nm, the resistivity was approximately 0.09 Ω·cm, and the carrier concentration was approximately 2 × 10⁻⁶. 19 cm -3 .

[0062] (3) Fabrication of low-resistivity oxide semiconductor interlayer

[0063] A low-resistivity oxide semiconductor interlayer is grown on the gallium oxide interlayer prepared in step (2). A BGZO thin film is selected as this interlayer, and a ZnO target doped with B and Ga elements is chosen, wherein the ZnO purity is 99.99%, and it is doped with 0.2 wt.% B₂O₃ and 1.8 wt.% Ga₂O₃. The base vacuum of the sputtering cavity is 10... -7 Torr fills the cavity with high-purity argon gas, controlling the sputtering pressure to 6 × 10⁻⁶. -3 The sputtering power was 150W, and the tray rotation speed was controlled at 5 rad / min. After the fabrication process was completed, a low-resistivity oxide semiconductor interlayer was obtained. The interlayer thickness was approximately 100 nm, the resistivity was approximately 0.002 Ω·cm, and the carrier concentration was approximately 3 × 10⁻⁶. 20 cm -3 .

[0064] (4) Preparation of Cr metal electrode

[0065] A 100 nm Cr electrode layer was grown on the low-resistivity gallium oxide intermediate layer grown in steps (2) and (3) using electron beam evaporation deposition. High-purity Cr was used, and the metal purity was calculated as 99.999% based on the proportion of impurities in the metal. The electron beam voltage was 9.7 keV, the power was set to 39%, and the growth rate was controlled using a crystal oscillator. The growth rate of Cr was... The growth temperature was room temperature. The electrode was then removed from the cavity to obtain a composite electrode for gallium oxide.

[0066] Example 4:

[0067] This embodiment is basically the same as the previous embodiments, except that:

[0068] In this embodiment, the gallium oxide device uses an ohmic contact composite electrode structure. The composite electrode structure that forms an ohmic contact with the gallium oxide material adopts a combination of a low-resistivity composite interlayer and a metal electrode. The entire structure is assembled by stacking four parts in sequence: β-Ga₂O₃ material, a low-resistivity doped gallium oxide interlayer, a low-resistivity oxide semiconductor interlayer, and a metal electrode. First, a low-resistivity doped gallium oxide interlayer with V as the dopant element is grown on the β-Ga₂O₃ using magnetron sputtering. Then, a low-resistivity BGZO thin film interlayer is grown on the doped gallium oxide interlayer using magnetron sputtering. Finally, a metal electrode is grown on the low-resistivity composite interlayer using electron beam evaporation. High-purity Cr with a purity of 99.999% is selected as the material for electron beam evaporation, based on the proportion of impurity concentration in the metal as the calculation method for metal purity.

[0069] A method for fabricating an ohmic contact composite electrode for gallium oxide devices includes the following steps:

[0070] (1) Material cleaning and pretreatment:

[0071] β-Ga2O3 material with a size of 20mm×20mm was selected and ultrasonicated for 6 minutes in deionized water, acetone, anhydrous ethanol and deionized water respectively. After being dried with high-purity nitrogen, a clean and dry β-Ga2O3 material was obtained, which improved the surface state of the material. Then the cleaned β-Ga2O3 material was quickly transferred into a vacuum chamber.

[0072] (2) Fabrication of low-resistivity doped gallium oxide interlayer

[0073] The cleaned β-Ga2O3 material from step (1) is placed into the vacuum chamber. A gallium oxide target doped with V is selected, with a gallium oxide purity of 99.99% and 5 at.% V2O5 doping. The base vacuum of the chamber is 10. -7 Torr is activated, the tray rotates at a rate of 5 rad / min, the substrate temperature is raised to 700℃ (heating rate: 10℃ / min), high-purity argon gas is introduced into the cavity, and the sputtering pressure is controlled at 6 × 10⁻⁶. -3 The sputtering power was 150 W. After the fabrication process, the film was allowed to cool naturally to room temperature, and the resulting low-resistivity doped gallium oxide interlayer was obtained. The interlayer thickness was approximately 50 nm, the resistivity was approximately 1.2 Ω·cm, and the carrier concentration was approximately 9 × 10⁻⁶. 18 cm -3 .

[0074] (3) Fabrication of low-resistivity oxide semiconductor interlayer

[0075] A low-resistivity oxide semiconductor interlayer is grown on the gallium oxide interlayer prepared in step (2). A BGZO thin film is selected as this interlayer, and a ZnO target doped with B and Ga elements is chosen, wherein the ZnO purity is 99.99%, and it is doped with 0.2 wt.% B₂O₃ and 1.8 wt.% Ga₂O₃. The base vacuum of the sputtering cavity is 10... -7 Torr fills the cavity with high-purity argon gas, controlling the sputtering pressure to 6 × 10⁻⁶. -3 The sputtering power was 150W, and the tray rotation speed was controlled at 5 rad / min. After the fabrication process was completed, a low-resistivity oxide semiconductor interlayer was obtained. The interlayer thickness was approximately 100 nm, the resistivity was 0.002 Ω·cm, and the carrier concentration was 3 × 10⁻⁶. 20 cm -3 .

[0076] (4) Preparation of Cr metal electrode

[0077] A 100 nm Cr electrode layer was grown on the low-resistivity composite intermediate layer prepared in steps (2) and (3) using electron beam evaporation deposition. High-purity Cr was used, and the metal purity was calculated as 99.999% based on the concentration ratio of impurities in the metal. The electron beam voltage was 9.7 keV, the power was set to 39%, and the growth rate was controlled using a crystal oscillator. The growth rate of Cr was... The growth temperature was room temperature. The electrode was then removed from the cavity to obtain a composite electrode for gallium oxide.

[0078] Example 5:

[0079] This embodiment is basically the same as the previous embodiments, except that:

[0080] In this embodiment, the gallium oxide device uses an ohmic contact composite electrode structure. The composite electrode structure that forms an ohmic contact with the gallium oxide material adopts a combination of a low-resistivity composite interlayer and a metal electrode. The entire structure is assembled by stacking four parts in sequence: amorphous Ga2O3 material, a low-resistivity doped gallium oxide interlayer, a low-resistivity oxide semiconductor interlayer, and a metal electrode. First, a low-resistivity doped gallium oxide interlayer with Ta as the dopant element is grown on β-Ga2O3 using magnetron sputtering. Then, a low-resistivity BGZO thin film interlayer is grown on the doped gallium oxide interlayer using magnetron sputtering. Finally, a metal electrode is grown on the low-resistivity composite interlayer using electron beam evaporation. High-purity Au with a purity of 99.999% is selected as the material for electron beam evaporation, based on the proportion of impurity concentration in the metal as the calculation method for metal purity.

[0081] A method for fabricating an ohmic contact composite electrode for gallium oxide devices includes the following steps:

[0082] (1) Material cleaning and pretreatment:

[0083] Amorphous Ga2O3 material with a size of 20mm×20mm was selected and ultrasonicated for 6 minutes in deionized water, acetone, anhydrous ethanol and deionized water respectively. After being dried with high-purity nitrogen, a clean and dry amorphous Ga2O3 material was obtained, which improved the surface state of the material. Then the cleaned amorphous Ga2O3 material was quickly transferred into a vacuum chamber.

[0084] (2) Fabrication of low-resistivity doped gallium oxide interlayer

[0085] The cleaned amorphous Ga2O3 material from step (1) is placed into the vacuum chamber. A gallium oxide target doped with Ta is selected, with a gallium oxide purity of 99.99% and 10 at.% Ta2O5 doping. The base vacuum of the chamber is 10. -7 Torr is activated, the tray rotates at a rate of 5 rad / min, the substrate temperature is raised to 700℃ (heating rate: 10℃ / min), high-purity argon gas is introduced into the cavity, and the sputtering pressure is controlled at 6 × 10⁻⁶. -3 The sputtering power was 150 W. After the fabrication process, the film was allowed to cool naturally to room temperature, and the resulting low-resistivity doped gallium oxide interlayer was obtained. The interlayer thickness was approximately 50 nm, the resistivity was approximately 0.09 Ω·cm, and the carrier concentration was approximately 2 × 10⁻⁶. 19 cm -3 .

[0086] (3) Fabrication of low-resistivity oxide semiconductor interlayer

[0087] A low-resistivity oxide semiconductor interlayer is grown on the gallium oxide interlayer prepared in step (2). A BGZO thin film is selected as this interlayer, and a ZnO target doped with B and Ga elements is chosen, wherein the ZnO purity is 99.99%, and it is doped with 0.2 wt.% B₂O₃ and 1.8 wt.% Ga₂O₃. The base vacuum of the sputtering cavity is 10... -7 Torr fills the cavity with high-purity argon gas, controlling the sputtering pressure to 6 × 10⁻⁶. -3 The sputtering power was 150W, and the tray rotation speed was controlled at 5 rad / min. After the fabrication process was completed, a low-resistivity oxide semiconductor interlayer was obtained. The interlayer thickness was approximately 100 nm, the resistivity was approximately 0.002 Ω·cm, and the carrier concentration was approximately 3 × 10⁻⁶. 20 cm -3 .

[0088] (4) Preparation of Au metal electrode

[0089] A 100 nm Au electrode layer was grown on the low-resistivity composite intermediate layer grown in steps (2) and (3) using electron beam evaporation deposition. High-purity Au was used, and the metal purity was calculated as 99.999% based on the proportion of impurities in the metal. The electron beam voltage was 9.7 keV, the power was set to 39.6%, and the growth rate was controlled using a crystal oscillator. The growth rate of Au was... The growth temperature was room temperature. The electrode was then removed from the cavity to obtain a composite electrode for gallium oxide.

[0090] In summary, the ohmic contact composite electrode for gallium oxide devices adopts a combination of a low-resistivity composite interlayer and a metal electrode to form the ohmic contact with the gallium oxide material. The entire structure is composed of four parts stacked sequentially: gallium oxide material, a low-resistivity doped gallium oxide interlayer, a low-resistivity oxide semiconductor interlayer, and a metal electrode. The gallium oxide material can include single-crystal, polycrystalline, and amorphous gallium oxide. The above embodiment addresses the problem of interface reactions easily caused during the alloying process of traditional multilayer metal electrodes by introducing low-resistivity composite semiconductor interlayer technology. This novel composite electrode reduces the influence of the interface, achieving a more stable ohmic contact with the gallium oxide material, thus making the electrical performance of gallium oxide devices more reliable and showing broad development prospects in the field of gallium oxide power electronic devices.

[0091] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Various changes can be made according to the purpose of the invention. Any changes, modifications, substitutions, combinations or simplifications made based on the spirit and principle of the technical solution of the present invention shall be equivalent substitutions. As long as they meet the purpose of the invention and do not deviate from the preparation method, technical principle and inventive concept adopted by the present invention, they shall fall within the protection scope of the present invention.

Claims

1. An ohmic contact composite electrode for gallium oxide devices, characterized in that: The composite electrode structure, which adopts a combination of low-resistivity composite intermediate layer and metal electrode, forms an ohmic contact with gallium oxide material. The whole structure is composed of four parts stacked and assembled sequentially: gallium oxide material, low-resistivity doped gallium oxide intermediate layer, low-resistivity oxide semiconductor intermediate layer and metal electrode.

2. The ohmic contact composite electrode for gallium oxide devices according to claim 1, characterized in that: The composite electrode is not limited to the crystal form of gallium oxide and can be used for single-crystal, polycrystalline, and amorphous gallium oxide.

3. The ohmic contact composite electrode for gallium oxide devices according to claim 1, characterized in that: The low-resistivity doped gallium oxide intermediate layer is selected to be doped with any element from Ta or V.

4. The ohmic contact composite electrode for gallium oxide devices according to claim 1, characterized in that: Use materials with a resistivity not higher than 2 Ω·cm and a carrier concentration not lower than 10. 17 cm -3 A gallium oxide doped thin film is used as the intermediate layer.

5. The ohmic contact composite electrode for gallium oxide devices according to claim 1, characterized in that: A gallium oxide intermediate layer is grown using magnetron sputtering. The purity of the target material is calculated based on the concentration ratio of impurities in the target material. The target material has a gallium oxide purity of not less than 99.99% and a doping element content of not more than 10 at.%.

6. The ohmic contact composite electrode for gallium oxide devices according to claim 1, characterized in that: Use materials with a resistivity not exceeding 0.02 Ω·cm and a carrier concentration not less than 10. 19 cm -3 The oxide semiconductor thin film is used as a low-resistivity oxide semiconductor intermediate layer.

7. The ohmic contact composite electrode for gallium oxide devices according to claim 1, characterized in that: The thickness of the gallium oxide doped interlayer is 1–100 nm; the thickness of the low-resistivity oxide semiconductor interlayer is 1–200 nm; and the thickness of the metal electrode is 1–200 nm.

8. A method for fabricating an ohmic contact composite electrode for gallium oxide devices, characterized in that, Includes the following steps: (1) Fabrication of low-resistivity doped gallium oxide interlayer A gallium oxide doped intermediate layer film was grown on pure gallium oxide using magnetron sputtering. A gallium oxide target containing doped elements was selected, with a gallium oxide purity ≥ 99.99%. The base vacuum of the sputtering cavity was ≤ 10 °C. -6 Torr, substrate temperature 100–900°C, high-purity argon gas is introduced into the cavity, and the sputtering pressure is controlled at 10. -3 ~10 -2 Torr sputtering power is 10-200W, the tray is rotatable, the growth thickness is controlled from 1 to 100nm, after the preparation process is completed, the film is allowed to cool naturally to room temperature, and then it is taken out to obtain a low-resistivity doped gallium oxide intermediate layer. (2) Fabrication of low-resistivity oxide semiconductor interlayer A low-resistivity oxide semiconductor interlayer is grown on the gallium oxide interlayer prepared in step (1); A BGZO thin film was selected as the intermediate layer, and a ZnO target doped with boron and gallium (99.99% purity) was chosen. The ZnO target was doped with 0.1–1 wt.% B₂O₃ and 1–1.9 wt.% Ga₂O₃. The base vacuum of the sputtering cavity was ≤10 °C. -6 Torr fills the cavity with high-purity argon gas, controlling the sputtering pressure to 10. -3 ~10 -2 Torr sputtering power is 10-200W, the tray is rotatable, the growth thickness is controlled to be 1-200nm, and after the fabrication process is completed, the low-resistivity oxide semiconductor intermediate layer is obtained by taking it out. (3) Preparation of metal electrodes A metal electrode is grown on the low-resistivity composite interlayer prepared in steps (1) and (2). The purity of the metal material is calculated by using the concentration ratio of impurities in the material as the target material. A high-purity metal with a purity of 99-99.9999% is selected. An electron beam evaporation deposition method is used to grow a metal electrode with a thickness of 1-200 nm on the low-resistivity interlayer. The electrode is then removed from the cavity to obtain an ohmic contact composite electrode for gallium oxide devices.

9. The method for preparing an ohmic contact composite electrode for gallium oxide devices according to claim 8, characterized in that: In step (3), the metal target of the metal electrode is at least any one of gold, titanium, aluminum or chromium.

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