Power diode device and preparation method thereof

Abstract

The invention belongs to the technical field of ultra-wide bandgap semiconductors, and particularly relates to a power diode device and a preparation method thereof, MXene is adopted as a Schottky anode material, and the series resistance is remarkably reduced by using the ultrahigh conductivity of the MXene, so that the performance of the device in high-frequency and large-current application is improved. Meanwhile, by regulating and controlling the surface terminal and the element composition of the MXene, the flexible adjustment of the work function can be realized, so that the electron affinity of the MXene can be well matched with that of beta-Ga2O3, a higher Schottky barrier and an excellent rectification characteristic can be further obtained, and the reverse leakage current can be inhibited. In addition, as a two-dimensional material, MXene can form a uniform and flat Van der Waals contact interface, so that the damage of a high-energy process is avoided, the surface integrity of beta-Ga2O3 is maintained, the interface state and Fermi level pinning effect are effectively relieved, the barrier height better conforms to the theoretical design, and the Schottky diode with the performance closer to the ideal state can be realized.

Description

Technical Field

[0001] This invention belongs to the field of ultra-wide bandgap semiconductor technology, specifically relating to power diode devices and their fabrication methods. Background Technology

[0002] Ultra-wide bandgap semiconductors (UWBGs), due to their superior physical properties, have been recognized by the international power semiconductor technology roadmap as an ideal material system for next-generation power electronic devices and are hailed as the "ultimate" semiconductor. Within this material system, gallium oxide (GaN) β Gallium oxide (Ga₂O₃) has attracted significant attention due to its outstanding performance advantages: its ultra-wide bandgap (~4.9 eV) significantly improves the breakdown voltage capability of devices; its strong critical breakdown field strength (8 MV / cm) makes it competitive in high-voltage applications; its high electron mobility (250 cm² / V·s) and excellent Baliga figure of merit (~3444) ensure low conduction losses; in addition, the commercially viable fabrication of large-size single-crystal substrates further promotes its practical application. Based on these characteristics, gallium oxide-based power diodes exhibit advantages such as low conduction losses, high temperature resistance, and fast switching, and have important application prospects in key areas such as high-efficiency energy conversion, smart grids, and new energy vehicles.

[0003] However, the industrialization of gallium oxide power diodes still faces several key challenges. First, their inherently low thermal conductivity (approximately 0.3 W / cm·K) easily leads to significant heat accumulation, limiting power dissipation capabilities. Currently, heterogeneous integration techniques (e.g., bonding with high thermal conductivity substrates) or advanced packaging solutions (e.g., flip-chip structures) can alleviate these thermal management challenges to some extent. However, the more fundamental challenge lies in the extreme difficulty of achieving p-type doping. This bottleneck not only hinders the development of bipolar devices (such as PN junction diodes and transistors) but may also cause electric fields to concentrate in edge regions, affecting the long-term reliability of the devices.

[0004] Against this backdrop, Schottky barrier diodes (SBDs) have become an important research direction for gallium oxide power devices. Compared with traditional PN junction diodes, SBDs, as majority carrier devices, have several significant advantages: First, they have extremely fast switching speeds, which can significantly reduce switching losses and are suitable for high-frequency applications; second, they do not have minority carrier storage effects, which is beneficial to improving the reverse recovery performance of the device; third, in the absence of effective p-type doping, the SBD structure can avoid the process complexity and reliability problems caused by p-type region fabrication, making it easier to realize high-performance unipolar devices.

[0005] From a development perspective, gallium oxide Schottky diodes show great potential in next-generation high-efficiency, high-power-density power electronic systems, especially in applications within the medium-to-high voltage range (600–3300V). Future research will focus on optimizing Schottky contact characteristics, improving edge termination structures to suppress electric field density, enhancing device thermal management capabilities, and exploring heterogeneous integration schemes with wide-bandgap semiconductors (such as SiC or diamond) with better thermal conductivity, gradually promoting their large-scale industrial application.

[0006] Existing technology 1 In the field of wide-bandgap semiconductor power devices, p-type β The absence of Ga2O3 has been a key bottleneck restricting the development of its PN junction devices. To solve this problem, researchers have proposed a heterojunction approach, which involves introducing other p-type semiconductors (such as NiO or Cu2O) with... β -Ga2O3 is combined to construct high-performance device structures. Currently, heteroepitaxial p-type NiO films are combined with... β -Ga2O3 has become the most feasible solution for constructing PN junctions. Currently reported NiO / β -Ga2O3 heterojunction diodes have achieved a reverse breakdown voltage of >1kV and an on-resistance of <1 mΩ·cm².

[0007] p-type NiO exhibits significant performance disadvantages in constructing heterojunction power diodes due to its poor conductivity. Specifically, NiO material inherently possesses low hole mobility (typically <1 cm⁻¹). 2 ( / V·s) and high resistivity (approximately 10) 5 The high on-resistance (RΩ·cm) of p-type NiO-based PN junction diodes results in a high on-resistance (RΩ·cm). on This high conduction characteristic raises two key issues: (1) under forward bias, the device will generate significant power dissipation; (2) the Joule heating effect during high current operation will exacerbate the device temperature rise, thereby affecting the device's reliability and long-term stability. Furthermore, the heterojunction interface formed between NiO and common n-type semiconductors (such as SiC or GaN) may have a high potential barrier, which further limits carrier transport efficiency, leading to increased forward turn-on voltage and deteriorated reverse recovery characteristics. These factors collectively restrict the application prospects of P-type NiO in high-voltage, high-power diodes, especially in power electronic systems requiring low power consumption and high efficiency.

[0008] Existing technology 2 Using traditional metal electrodes (such as Ni and Au) with gallium oxide as Schottky contacts offers advantages such as good conductivity and a high Schottky barrier. However, during traditional metal-semiconductor deposition, high-energy metal atoms can damage the semiconductor surface, creating interface states that "pin" the Fermi level to a specific energy level. This makes the Schottky barrier height almost independent of the metal's work function, making it difficult to control. Furthermore, traditional metal thin films are prone to island growth or interface defects during deposition, leading to localized electric field enhancement ("spiking" effect). This results in leakage current at actual operating voltages being much higher than theoretical values, and a significant breakdown voltage drop.

[0009] current β Ga2O3 Schottky diodes still have several limitations, such as high series resistance, Fermi level pinning caused by interface states, and difficulty in precisely controlling the Schottky barrier height, which limits the performance of the devices under high-frequency and high-current operating conditions. MXene, as an ideal metal contact material, is expected to effectively address these limitations. β The key challenges in performance optimization of Ga2O3-based Schottky diodes have driven the fabrication of high-performance devices. To address this, this invention proposes a power diode device and its fabrication method. Summary of the Invention

[0010] The purpose of this invention is to provide a power diode device and its fabrication method, which can effectively address the challenges of... β The key challenges in performance optimization of Ga2O3-based Schottky diodes have driven the fabrication of high-performance devices.

[0011] The specific technical solution adopted by this invention is as follows: A power diode device, from bottom to top, includes: a cathode ohmic contact electrode layer a, β -Ga2O3 single crystal substrate b, MXene layer c, anode PAD electrode layer d; The cathode ohmic contact electrode layer a structure is selected from any of the following combinations: titanium / gold (Ti / Au) bilayer structure; titanium / aluminum (Ti / Al) bilayer structure; titanium / gold / titanium / aluminum (Ti / Au / Ti / Al) multilayer structure; each metal layer is prepared by magnetron sputtering, wherein: the deposition thickness of the titanium (Ti) layer is 10nm to 50nm; the deposition thickness of the gold (Au) layer is 80nm to 500nm; the thickness of the aluminum (Al) layer is determined according to the specific implementation method; experimental verification shows that the above three metal layer structures have equivalent electrical properties and contact characteristics when forming ohmic contacts; The β -The Ga2O3 single crystal substrate b can be an unintentionally doped or lightly doped substrate, or it can be a homoepitaxial lightly doped layer (doping concentration of 10) on an unintentionally doped substrate. 16 ~10 17 / cm 3 The substrate crystal orientation can be (010), (-201), (100) or (001); The MXene layer c is composed of a single layer of MXene material and forms a Schottky barrier contact with Ga2O3. The anode PAD electrode layer d uses conductive silver paste (Ag paste) as the electrode material to form an ohmic contact with the MXene layer.

[0012] A method for fabricating a power diode device includes the following steps: Step 1: Substrate cleaning; Step 1 specifically includes the following steps: Step 101: Organic cleaning: Use acetone, ethanol, and deionized water in sequence for ultrasonic cleaning to remove organic contaminants; Step 102: Inorganic cleaning: Soak in diluted hydrofluoric acid (HF:H2O=1:10) or hydrochloric acid (HCl:H2O=1:5) solution to remove the natural oxide layer on the surface; Step 103: Dry with nitrogen and then store under vacuum.

[0013] Step 2: Fabrication of ohmic contact electrode; Step 2 includes the following specific steps: Step 201: Deposit a Ti / Au or Ti / Al multilayer metal structure on the back of a single crystal Ga2O3 by magnetron sputtering, wherein the thickness of the Ti layer is 10-50 nm and the thickness of the Au / Al layer is 80-500 nm. Step 202: Perform rapid thermal annealing (RTA) in a nitrogen atmosphere at a temperature of 400-600°C for 30-90 seconds to form an ohmic contact.

[0014] Step 3: Fabrication of MXene Schottky electrode.

[0015] Step 3 includes the following steps: Step 301: Preparation of MXene Schottky contact layer: MXene dispersion is quantitatively transferred to the Ga2O3 surface using a micropipette; the amount of each drop is 5-20 μL, and a single-layer MXene film is formed by drying at a low temperature of 50-100℃; the drop is repeated 2-5 times to adjust the film thickness to 5-50 nm; Step 302: Electrode lead-out: Coat the surface of the MXene layer with conductive silver paste and cure at 70-120℃ to form electrode contacts.

[0016] The technical effects achieved by this invention are as follows: This invention uses, for example, Ti3C2T xMXene, as a Schottky anode material, utilizes its ultra-high conductivity (exceeding 10,000 S / cm) to significantly reduce series resistance, thereby improving device performance in high-frequency and high-current applications. Furthermore, by controlling the surface terminals (-O, -OH, -F, etc.) and elemental composition of MXene, its work function can be flexibly adjusted to match... β The electron affinity of Ga2O3 (approximately 4.0–4.3 eV) provides a good match, resulting in a high Schottky barrier and excellent rectification characteristics, suppressing reverse leakage current. Furthermore, MXene, as a two-dimensional material, can form a uniform and flat van der Waals interface, avoiding damage from high-energy processes and maintaining... β - The surface integrity of Ga2O3 effectively alleviates the pinning effect of interface states and Fermi level, making the barrier height more consistent with the theoretical design, which is conducive to realizing Schottky diodes with performance closer to the ideal state. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the device structure of the present invention; Figure 2 The current-voltage characteristic log plot is used to test the developed device; Figure 3 Linear plot of current-voltage characteristics for testing the developed device; Figure 4 The graph shows the relationship between the resistance of the device and the voltage (-2V~2V). Detailed Implementation

[0018] To make the objectives and advantages of this invention clearer, the invention will be specifically described below with reference to embodiments. It should be understood that the following text is merely used to describe one or more specific embodiments of the invention and does not strictly limit the scope of protection specifically claimed by the invention.

[0019] Example 1: like Figure 1 As shown, the power diode device, from bottom to top, includes: a cathode ohmic contact electrode layer a, β -Ga2O3 single crystal substrate b, MXene layer c, anode PAD electrode layer d; The cathode ohmic contact electrode layer a structure is selected from any of the following combinations: titanium / gold (Ti / Au) bilayer structure; titanium / aluminum (Ti / Al) bilayer structure; titanium / gold / titanium / aluminum (Ti / Au / Ti / Al) multilayer structure; each metal layer is prepared by magnetron sputtering, wherein: the deposition thickness of the titanium (Ti) layer is 10nm to 50nm; the deposition thickness of the gold (Au) layer is 80nm to 500nm; the thickness of the aluminum (Al) layer is determined according to the specific implementation method; experimental verification shows that the above three metal layer structures have equivalent electrical properties and contact characteristics when forming ohmic contacts; The β -The Ga2O3 single crystal substrate b can be an unintentionally doped or lightly doped substrate, or it can be a homoepitaxial lightly doped layer (doping concentration of 10) on an unintentionally doped substrate. 16 ~10 17 / cm 3 The substrate crystal orientation can be (010), (-201), (100) or (001); The MXene layer c is composed of a single layer of MXene material and forms a Schottky barrier contact with Ga2O3. The anode PAD electrode layer d uses conductive silver paste (Ag paste) as the electrode material to form an ohmic contact with the MXene layer.

[0020] This invention uses, for example, Ti3C2T x MXene, as a Schottky anode material, utilizes its ultra-high conductivity (over 10,000 S / cm) to significantly reduce series resistance, thereby improving device performance in high-frequency and high-current applications. Furthermore, by controlling the surface terminals (-O, -OH, -F, etc.) and elemental composition of MXene, its work function can be flexibly adjusted to match... β The electron affinity of Ga2O3 (approximately 4.0–4.3 eV) provides a good match, resulting in a high Schottky barrier and excellent rectification characteristics, suppressing reverse leakage current. Furthermore, MXene, as a two-dimensional material, can form a uniform and flat van der Waals interface, avoiding damage from high-energy processes and maintaining... β - The surface integrity of Ga2O3 effectively alleviates the pinning effect of interface states and Fermi level, making the barrier height more consistent with the theoretical design, which is conducive to realizing Schottky diodes with performance closer to the ideal state.

[0021] Example 2: A method for fabricating a power diode device includes the following steps: Step 1: Substrate cleaning; Step 1 specifically includes the following steps: Step 101: Organic cleaning: Use acetone, ethanol, and deionized water in sequence for ultrasonic cleaning to remove organic contaminants; Step 102: Inorganic cleaning: Soak in diluted hydrofluoric acid (HF:H2O=1:10) or hydrochloric acid (HCl:H2O=1:5) solution to remove the natural oxide layer on the surface; Step 103: Dry with nitrogen and then store under vacuum.

[0022] Step 2: Fabrication of ohmic contact electrode; Step 2 includes the following specific steps: Step 201: Deposit a Ti / Au or Ti / Al multilayer metal structure on the back of a single crystal Ga2O3 by magnetron sputtering, wherein the thickness of the Ti layer is 10-50 nm and the thickness of the Au / Al layer is 80-500 nm. Step 202: Perform rapid thermal annealing (RTA) in a nitrogen atmosphere at a temperature of 400-600°C for 30-90 seconds to form an ohmic contact.

[0023] Step 3: Fabrication of MXene Schottky electrode.

[0024] Step 3 includes the following steps: Step 301: Preparation of MXene Schottky contact layer: MXene dispersion is quantitatively transferred to the Ga2O3 surface using a micropipette; the amount of each drop is 5-20 μL, and a single-layer MXene film is formed by drying at a low temperature of 50-100℃; the drop is repeated 2-5 times to adjust the film thickness to 5-50 nm; Step 302: Electrode lead-out: Coat the surface of the MXene layer with conductive silver paste and cure at 80-120℃ to form electrode contacts.

[0025] This embodiment is specifically exemplified as follows: Step 1: Use acetone, ethanol, and deionized water in sequence for ultrasonic cleaning to remove organic contaminants.

[0026] Step 2: Deposit a Ti / Al (20 / 300nm) multilayer metal structure on the back side of a (001) Ga2O3 single crystal by magnetron sputtering.

[0027] Step 3: Perform rapid thermal annealing (RTA) in a nitrogen atmosphere at a temperature of 500°C to form an ohmic contact.

[0028] Step 4: Quantitatively transfer the MXene dispersion onto the Ga2O3 front side using a micropipette; each drop is 5 μL, and the film is dried at 60°C to form a monolayer MXene film. Repeat the drop-coating process 3 times to adjust the film thickness.

[0029] Step 5: Coat the surface of the MXene layer with conductive silver paste and cure at 70°C to form electrode contacts.

[0030] like Figures 2-4 As shown, based on the I / O characteristic curve analysis of this Schottky diode, the device exhibits several superior performance characteristics: First, it has a low turn-on voltage of approximately 1 V and an on-resistance of 0.02 mΩ·mm, ensuring high efficiency and low power consumption under low-voltage, high-current operating conditions; second, it has a high on / off ratio (10-1). 7 ~10 8 Finally, as a majority carrier conducting device, it possesses ultrafast switching characteristics. These advantages make it ideal for high-frequency rectification, low-voltage power management, and radio frequency applications.

[0031] The above description is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described or explained in this invention are implemented according to conventional methods in the art unless otherwise specified or limited.

Claims

1. A power diode device, characterized in that: From bottom to top, it includes: cathode ohmic contact electrode layer a, β -Ga2O3 single crystal substrate b, MXene layer c, anode PAD electrode layer d; The cathode ohmic contact electrode layer a structure is selected from any combination of the following: titanium / gold bilayer structure; titanium / aluminum bilayer structure; titanium / gold / titanium / aluminum multilayer structure; each metal layer is prepared by magnetron sputtering process, wherein: the deposition thickness of the titanium layer is 10nm to 50nm; the deposition thickness of the gold layer is 80nm to 500nm; the thickness of the aluminum layer is determined according to the specific implementation method; The β - The Ga2O3 single crystal substrate b is selected from unintentionally doped or lightly doped substrates, or a homogeneous epitaxial lightly doped layer on an unintentionally doped substrate; the doping concentration is 10. 16 ~10 17 / cm 3 The substrate crystal orientation is (010), (-201), (100) or (001); The MXene layer c is composed of a single layer of MXene material and forms a Schottky barrier contact with Ga2O3. The anode PAD electrode layer d uses conductive silver paste as the electrode material to form an ohmic contact with the MXene layer.

2. A method for fabricating a power diode device, characterized in that: The preparation method is used to prepare the power diode device of claim 1, and includes the following steps: Step 1: Substrate cleaning; Step 2: Fabrication of ohmic contact electrode; Step 3: Fabrication of MXene Schottky electrode.

3. The method for fabricating the power diode device according to claim 2, characterized in that: Step 1 specifically includes the following steps: Step 101: Organic cleaning: Use acetone, ethanol, and deionized water in sequence for ultrasonic cleaning to remove organic contaminants; Step 102: Inorganic cleaning: Soak in a diluted hydrofluoric acid solution of HF:H2O=1:10 or hydrochloric acid solution of HCl:H2O=1:5 to remove the natural oxide layer on the surface; Step 103: Dry with nitrogen and then store under vacuum.

4. The method for fabricating the power diode device according to claim 2, characterized in that: Step 2 includes the following specific steps: Step 201: Deposit a Ti / Au or Ti / Al multilayer metal structure on the back of a single crystal Ga2O3 by magnetron sputtering, wherein the thickness of the Ti layer is 10-50 nm and the thickness of the Au / Al layer is 80-500 nm. Step 202: Perform rapid thermal annealing (RTA) in a nitrogen atmosphere at a temperature of 400-600℃ for 30-90 seconds to form an ohmic contact.

5. The method for fabricating the power diode device according to claim 2, characterized in that: Step 3 includes the following steps: Step 301: Preparation of MXene Schottky contact layer: MXene dispersion is quantitatively transferred to the Ga2O3 surface using a micropipette; the amount of each drop is 5-20 μL, and a single-layer MXene film is formed by drying at a low temperature of 50-100℃; the drop is repeated 2-5 times to adjust the film thickness to 5-50 nm; Step 302: Electrode lead-out: Coat the surface of the MXene layer with conductive silver paste and cure at 80-120℃ to form electrode contacts.

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