Table of Content

15 March 2025, Volume 54 Issue 3

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Crystal Growth, Doping and Defects

Review on Mg Doping of Ga₂O₃

SUN Rujun, ZHANG Jinghui, LI Yifan, HAO Yue, ZHANG Jincheng

2025, 54(3):  361-370.  doi:10.16553/j.cnki.issn1000-985x.2024.0295

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Gallium oxide (Ga₂O₃) possesses an ultra-wide bandgap and high breakdown electric field, making it promising for applications in power electronic devices and optoelectronic devices. Although Ga₂O₃ lacks p-type conductivity, we can still utilize p-type doping to control and design electrical properties by energy band engineering. The p-type dopants for gallium oxide that have been experimentally verified include Mg, Fe, N, Zn, Cu, Ni, Co, etc. Among the p-type dopants of Ga₂O₃, Mg is extensively studied due to its lowest formation energy, closest energy level to the valence band top, and multiple doping methods. This paper focuses on Mg doping β-Ga₂O₃. Firstly, the theoretical computational understanding and experimental test results of the acceptor levels of Mg-doped Ga₂O₃ are reviewed. Secondly, various doping methods, doping concentrations, and key issues such as Mg diffusion during thermal treatment for semi-insulating single crystals and epitaxial layers of Mg-doped β-Ga₂O₃ are summarized. Finally, it is pointed out that further investigations are needed on the mechanisms of Mg incorporation, activation and diffusion.

First-Principle Study on the Interaction Between Al/In Doping and (100) Twins in β-Ga₂O₃

LI Qi, FU Bo, YU Bowen, ZHAO Hao, LIN Na, JIA Zhitai, ZHAO Xian, TAO Xutang

2025, 54(3):  371-377.  doi:10.16553/j.cnki.issn1000-985x.2024.0323

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As a new generation of ultra-wide bandgap semiconductor, β-Ga₂O₃ has significant application value in high-power devices and solar-blind detection devices, attracting extensive attention from researchers in recent years. However, the low symmetry of the monoclinic lattice of β-Ga₂O₃ leads to anisotropic formation energies for the planar defects, with the (100) twin boundary exhibiting a lower formation energy and being prevalent in β-Ga₂O₃. To explore the control methods and mechanisms for the formation of the β-Ga₂O₃ (100) twin boundary, the interactions between the Al/In dopants and the (100) twins using first-principles calculations were investigated in this paper. Analysis of the structure, energy, and electronic properties of the Al/In-doped β-Ga₂O₃ (100) twin boundary system indicates that the substitution of Ga in the twin system by Al/In significantly affects the formation energy of the (100) twin boundary. Notably, the incorporation of Al consistently raises the formation energy of the (100) twin boundary without significantly altering the bandgap, shifting the band edges, or introducing additional impurity levels within the bandgap. Therefore, Al/In incorporation is predicted to be a potential strategy for influencing the formation of β-Ga₂O₃ (100) twin boundary. An appropriate incorporation of Al/In may help suppress the formation of the (100) twin boundary and improve the quality of β-Ga₂O₃ crystals.

Flow Field Symmetry of β-Ga₂O₃ Crystal Growth by EFG

JIANG Bowen, JI Weiguo, ZHANG Lu, FAN Qiming, PAN Mingyan, HUANG Haotian, QI Hongji

2025, 54(3):  378-385.  doi:10.16553/j.cnki.issn1000-985x.2025.0007

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The key to successful growth of high-quality gallium oxide (Ga₂O₃) single crystals by the edge-defined film-fed growth (EFG) method is the stable control of the shoulder, where a symmetrical flow and thermal field is one of the critical factors. This paper combines numerical simulation with experiments, introducing gas intakes at different positions in the insulation device to regulate the convective behavior of the gas within the insulation, thereby avoiding the negative impact of vortices on the thermal field above the mold. The study shows that bottom gas intake significantly enhances the symmetry of the thermal and flow fields near the solid-liquid interface, achieving an appropriate axial temperature gradient of 40 K/mm, and successfully realizing symmetrical shoulder during the crystal growth process. This achievement provides a foundation for the design and optimization of the EFG system for β-Ga₂O₃ single crystal growth.

Comparative Study on Thermal Field of Ga₂O₃ Single Crystal Growth Simulated by Different Thermal Radiation Models

YIN Changshuai, MENG Biao, LIANG Kang, CUI Hanwen, LIU Sheng, ZHANG Zhaofu

2025, 54(3):  386-395.  doi:10.16553/j.cnki.issn1000-985x.2024.0292

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High-quality gallium oxide (Ga₂O₃) single crystals were grown using the edge-defined film-fed growth method (EFG method), with the radiation heat transfer inside the furnace significantly impacting the temperature field distribution and stress distribution during the crystal growth process. Therefore, this study uses different finite element methods to analyze the three-dimensional thermal field distribution of Ga₂O₃ single crystal growth under three different radiation models, including the Rosseland method, the P1 approximation method, and the discrete ordinates method (DOM). A thermoelastic stress model is used to solve the stress distribution within the crystal under different heat flux conditions. Numerical simulation results indicate significant differences in the thermal field calculations under different radiation models. With the same heating power, the Rosseland radiation model has the smallest temperature gradient at the solid-liquid interface, while DOM has the largest temperature gradient. Under the same heat flux, the DOM radiation model exhibits the highest thermal stress during the early cooling stage, while the Rosseland model shows the highest thermal stress during the final cooling stage. Under varying heat flux conditions, the Rosseland radiation model displays the most significant changes in stress and temperature. This research provides theoretical guidance for the thermal field design in single crystal growth for gallium oxide and other related materials.

Evaluation and Control of Crystallization Interface Deformation in the Growth of 6-Inch β-Ga₂O₃ Crystals by EFG Method

WANG Junlan, LI Zaoyang, YANG Yao, QI Chongchong, LIU Lijun

2025, 54(3):  396-406.  doi:10.16553/j.cnki.issn1000-985x.2025.0006

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β-Ga₂O₃ single crystals exhibit exceptional properties, such as a wide bandgap and high breakdown field strength, making them highly valuable for applications in high-power and deep ultraviolet devices. The edge-defined film-fed growth (EFG) method is a critical technique for producing large and high-quality β-Ga₂O₃ single crystals. However, the circumferential symmetry of the heating and insulation structure inside the EFG furnace, coupled with the circumferential asymmetry of the die and the crystal, leads to significant heat transfer non-uniformity in the width and thickness directions of the crystal, resulting in severe crystallization interface deformation that impairs the stable growth of the crystal. This study comprehensively considers various heat transfer phenomena, including the coupling effects of anisotropic thermal conductivity and thermal radiation absorption in β-Ga₂O₃ single crystals. A dynamic mesh tracking method is implemented to model non-axisymmetric crystallization interface shapes, and a three-dimensional global heat transfer numerical model is developed for the EFG growth of β-Ga₂O₃ single crystals. The heat transfer and crystallization interface deformation during the growth of 2-inch and 6-inch (1 inch=2.54 cm) β-Ga₂O₃ single crystals were compared and analyzed. Interface deformation for crystals of different sizes was evaluated, and a cover structure was designed to reduce deformation during the growth of 6-inch crystals. The results show that the growth of 6-inch β-Ga₂O₃ single crystals exhibits more significant heat transfer non-uniformity in the width and thickness directions of the crystal. This results in larger crystallization interface deformation and poorer crystal growth stability for larger crystals. The cover structure has a significant influence on both heat transfer in the width and thickness directions of the crystal and interface deformation. A thick cover that circumferentially wraps the crystal can create favorable conditions for the stable growth of 6-inch β-Ga₂O₃ single crystals. This research provides valuable guidance for ensuring the stable growth of large, high-quality β-Ga₂O₃ single crystals by the EFG method.

Preparation and Properties of 3~4 Inch Fe Doped β-Ga₂O₃ Single Crystal with High Resistance

HUO Xiaoqing, ZHANG Shengnan, ZHOU Jinjie, WANG Yingmin, CHENG Hongjuan, SUN Qisheng

2025, 54(3):  407-413.  doi:10.16553/j.cnki.issn1000-985x.2025.0010

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Ultra-wide bandgap semiconductor β-Ga₂O₃ single crystal, which has excellent high breakdown field and low-cost potential, has attracted extensive attention from researchers. In this paper, 3~4 inch (1 inch=2.54 cm) Fe-doped β-Ga₂O₃ single crystals were grown by edge-defined film-fed growth method, the maximum length of which is 270 mm. A single crystals ingot could be cut to several bulk crystals with the large size, which effectively reduced the crystal growth cost. The electrical, optical and high-resolution X-ray diffraction full width at half maximum of the grown crystals were tested and analyzed. The data indicates good consistency in the electrical, optical, and XRD full width at half maximum of the wafers, demonstrating excellent crystal quality. Furthermore, the performance of a series of Fe-doped β-Ga₂O₃ single crystals were studied to analyze the influence of the Fe element on the quality, band gap and lattice vibration of β-Ga₂O₃ single crystals. It is found that, all the Fe-doped β-Ga₂O₃ single crystals have good crystalline quality. Fe doping can widen the bandgap of β-Ga₂O₃ single crystals, and meanwhile, induce a slight tensile stress in β-Ga₂O₃ single crystals. This paper will provide data support for substrate epitaxy and device verification.

Dislocation Defects and Their Distribution Characteristics in Ga₂O₃ Crystal Grown by Edge-Defined Film-Fed Growth Method

YANG Wenjuan, BU Yuzhe, SAI Qinglin, QI Hongji

2025, 54(3):  414-419.  doi:10.16553/j.cnki.issn1000-985x.2024.0304

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β-Ga₂O₃, as a new generation of ultra-wide bandgap semiconductor material, has garnered increasing attention due to its exceptional physical properties and high performance in devices. Various melt crystal growth techniques, such as the floating zone method and edge-defined film-fed growth (EFG) method, can be employed for the preparation of β-Ga₂O₃. Defects often exert significant adverse effects on the performance of semiconductor devices (e.g., higher leakage currents and lower breakdown voltages), making defect detection techniques for β-Ga₂O₃ crystals particularly crucial, especially for dislocation defects within linear defects. Traditionally, etching methods were used for the detection and density calculation of dislocations, but common methods for characterizing material defects are destructive and only applicable to the research analysis of experimental samples. In this paper, X-ray topography (XRT) and acid etching were utilized to investigate β-Ga₂O₃ grown by EFG method on (001), (010), and (100) surface, demonstrating the three-dimensional distribution characteristics of dislocations. It is shown that dislocations along the b-axis [010] direction dominate, providing valuable insights into the structure and characteristics of β-Ga₂O₃ dislocations. This, in turn, offers new directions for the subsequent selection of epitaxial and device crystal orientations.

Thin Film Epitaxy

ε-Ga₂O₃ Growth on c-Plane Sapphire Substrate with Metal-Organic Chemical Vapor Deposition

WANG Ziming, ZHANG Yachao, FENG Qian, LIU Shiteng, LIU Yuhong, WANG Yao, WANG Long, ZHANG Jincheng, HAO Yue

2025, 54(3):  420-425.  doi:10.16553/j.cnki.issn1000-985x.2024.0300

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In this paper, the growths of ε-Ga₂O₃ thin films on c-plane sapphire substrate by metal-organic chemical vapor deposition (MOCVD) via single-step and two-step growth methods were studied respectively. High-resolution X-ray single crystal diffraction was used to analyze the phase composition of Ga₂O₃ along the c-axis direction of the sapphire. In the single-step method, the thin film grows directly on the sapphire substrate. The β-Ga₂O₃ (402) peak can be observed at growth temperatures ranging from 360 ℃ to 425 ℃, while the ε-Ga₂O₃ (004) peak can also be detected at 370~410 ℃. Samples grown at 380 and 390 ℃ exhibit stronger ε-Ga₂O₃ (004) peaks with lower full width at half maximum (FWHM) and a surface roughness. The two-step growth method involves using an ε-Ga₂O₃ thin film grown at 380 ℃ as a buffer layer, followed by continuing the growth of ε-Ga₂O₃ thin films at 400~430 ℃. It is observed that the intensity of the ε-Ga₂O₃ (004) peak is higher than that of the single-step growth method, with even lower FWHM values. The rocking curve FWHM of the (004) peak of the film reaches 0.49° at continuing growth temperature of 430 ℃. Further adjustment of the pressure in the single-step growth method confirms that the buffer layer effectively promotes the growth of ε-Ga₂O₃ along the c-axis.

Study on the Epitaxial Growth of Gallium Oxide Heterostructure and UV Photodetector by Double Chamber Interconnected MOCVD

WANG Yuefei, GAO Chong, WU Zhe, LI Bingsheng, LIU Yichun

2025, 54(3):  426-437.  doi:10.16553/j.cnki.issn1000-985x.2024.0322

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This paper reports the epitaxial growth of Ga₂O₃/nitride thin film heterostructures using a nitrogen-oxide double chamber interconnected metal organic chemical vapor deposition (MOCVD) technique, achieving high-performance ultraviolet photodetector devices. The crystallization quality and surface morphology of the thin films were characterized using X-ray diffraction and atomic force microscopy for different substrates and buffer layer materials. Additionally, the ultraviolet photodetection performance of both planar and heterojunction Ga₂O₃ devices was studied using a photoelectric testing system. The results show that the introduction of an AlN buffer layer can reduce the lattice mismatch between the thin film and the substrate, effectively improving the crystallization quality of the epitaxial Ga₂O₃ thin films on different substrates. Utilizing the advantages of the double chamber, an AlN buffer layer on sapphire and p-Si (111) substrates was introduced respectively, resulting in β-Ga₂O₃ thin films with a preferred orientation of (201) and high structural quality, significantly enhancing the device performance of heterojunction blind ultraviolet photodetectors. Furthermore, we combined β-Ga₂O₃ with p-type GaN to fabricate a pn heterostructure and investigated the effect of different oxide layer thicknesses on the photodetection performance of the heterojunction. Ultimately, high-performance ultraviolet photodetector devices based on Ga₂O₃ were achieved.

Effect of Substrate Crystal Planes on the Properties of Homoepitaxial n-Ga₂O₃ Thin Films Grown by MOCVD

HAN Yu, JIAO Teng, YU Han, SAI Qinglin, CHEN Duanyang, LI Zhen, LI Yihan, ZHANG Zhao, DONG Xin

2025, 54(3):  438-444.  doi:10.16553/j.cnki.issn1000-985x.2024.0310

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The homoepitaxial growth of Si-doped n-type β-Ga₂O₃ thin films was achieved on Fe-doped (001), (010), and(201) β-Ga₂O₃ substrates using the metal-organic chemical vapor deposition (MOCVD) technique. The effects of substrate crystal planes on the crystal quality, growth rate, and electrical properties of the epitaxial films were systematically investigated. The results show that the homoepitaxial n-type β-Ga₂O₃ thin films exhibit the same crystallographic orientation as the substrates, with narrow full width at half maximum (FWHM) values in the rocking curves, indicating high crystal quality. The films demonstrate low surface roughness and exhibit step-flow growth characteristics. Significant differences in homoepitaxial growth rates were observed on substrates with different orientations, with the growth rate on the (001) substrate exceeding 1 μm/h. The n-type β-Ga₂O₃ thin films grown on the (010) substrate exhibit the highest carrier concentration and mobility, making them more promising for device fabrication. This study provides valuable data to support the development of Ga₂O₃-based devices.

A Novel Suboxide Chemical Vapor Transport Technique for Cost-Effective Growth of β-Ga₂O₃ Thick Films

CHEN Xuyang, LI Haobo, QIN Huayao, XU Mingyao, LU Yinmei, HE Yunbin

2025, 54(3):  445-451.  doi:10.16553/j.cnki.issn1000-985x.2024.0312

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As an ultra-wide bandgap semiconductor material, β-Ga₂O₃ has a broad application prospect in power devices. This work proposes a new method for fast epitaxial growth of crystalline β-Ga₂O₃ thick films: the suboxide chemical vapor transport (SOCVT), which has the advantages of simple operation and cost-effective. Using gaseous Ga₂O generated by the high-temperature reaction of liquid Ga and solid Ga₂O₃ as the Ga source, the growth of a β-Ga₂O₃ crystalline film, thicker than 100 μm, on the c-plane sapphire single-crystal substrate (1 cm×1 cm) was achieved in the CO₂ atmosphere at a setting temperature of 1 300 ℃ with the crucible-substrate spacing of 8.5 cm. According to the XRD analyses, the sample has a preferred orientation of (201). The SEM characterizations show that the deposited thick film is uniform and dense, with a thickness of 106.4 μm. XPS analyses reveal that the element O/Ga ratio of the thick film is 1.5, indicating its high chemical purity with no carbon-doping. The bandgap estimated from optical transmission spectrum is 4.42 eV. The research results indicate that the SOCVT technique offers a fast growth rate of β-Ga₂O₃, which is expected to become a new method for cost-effective and fast growth of crystalline β-Ga₂O₃ thick films.

Simulation Study on the Effect of Gallium Source Temperature on the Temperature Field in LPCVD Gallium Oxide Epitaxy

HU Jichao, ZHAO Qiyang, YANG Zhihao, YANG Ying, PENG Bo, DING Xiongjie, LIU Wei, ZHANG Hong

2025, 54(3):  452-461.  doi:10.16553/j.cnki.issn1000-985x.2024.0305

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The high temperature and intricate structure within the low pressure chemical vapor deposition (LPCVD) horizontal reactor chamber can result in uneven temperature distribution when reaction gases are introduced, ultimately influencing the quality of the resulting thin films. To achieve films of superior quality, a physical model of the reaction chamber is developed based on the reactor's equipment data. Using models of heat conduction, heat convection, and heat radiation, finite element simulation software is employed to simulate the multiphysical fields involved in the reaction process, including the flow field, thermal field, chemical reaction field, and dilute substance transfer field. By varying process parameters, such as the gallium source temperature, the simulation assesses the effect of temperature fluctuations within the LPCVD reaction chamber on the deposition characteristics of β-Ga₂O₃ thin films. The simulation results reveal that the uniformity of the films diminishes as the gallium source temperature increases, whereas the deposition rate of the films increases with temperature. Optimal film quality is obtained when the gallium source temperature is maintained between 900 and 950 ℃. By optimizing process parameters, the thickness and uniformity of the β-Ga₂O₃ films grown by LPCVD epitaxy are enhanced, leading to the fabrication of Ga₂O₃ devices with improved performance.

Preparation of Ga₂O₃∶Si Thin Films and Study on the Performance of Its Solar-Blind Ultraviolet Photodetectors

ZHANG Xian, YUE Zhiang, ZHAO Enqin, WEI Shuaikang, YE Wenxuan, HUANG Minyi, XIN Meibo, ZHAO Yang, WANG Hui

2025, 54(3):  462-469.  doi:10.16553/j.cnki.issn1000-985x.2024.0289

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Solar-blind ultraviolet photodetectors (SBPDs) exhibit significant potential for many fields, including military, civil, and medical sectors. In this paper, Si-doped Ga₂O₃ thinfilms were prepared by radio frequency magnetron sputtering. The effect of the argon-oxygen flow ratio on the physical properties of the films was studied. The analysis results of crystal structure, optical properties, and surface morphology indicate that the crystalline quality of the film is best when the argon-oxygen flow ratio is 30∶20. The Ga₂O₃∶Si thin film exhibits preferential growth along the (402) crystal plane, with a smooth and flat surface without micro-holes, and an average transmittance of 90% in the range of 400 nm to 800 nm. We fabricated p-GaN/n-Ga₂O₃∶Si self-powered SBPDs using optimized preparation parameters. Under 254 nm illumination at 0 V, the device shows rise time and decay time of 0.450 and 0.509 s, respectively. The light-dark current ratio (PDCR), responsivity (R), and specific detectivity (D^*) are 23, 0.24 mA/W, and 1.67×10⁸ Jones, respectively. The time-response characteristics of the device under 0~-6 V bias were studied. Under 0 V, the device has a spike in response at the 254 nm irradiation. When a reverse bias is applied, the spike disappear. Finally, the energy band diagrams of the p-GaN/Ga₂O₃∶Si heterojunction before contact, after contact, and under reverse bias are analyzed.

Device Fabrication

Research Progress on Heterogeneous Substrate Integration Technology for Gallium Oxide

QU Zhenyu, XU Wenhui, JIANG Haodong, LIANG Hengshuo, ZHAO Tiancheng, XIE Yinfei, SUN Huarui, ZOU Xinbo, YOU Tiangui, QI Hongji, HAN Genquan, OU Xin

2025, 54(3):  470-490.  doi:10.16553/j.cnki.issn1000-985x.2024.0315

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As a wide-bandgap semiconductor, β-Ga₂O₃ holds immense promise for high-power and radio frequency devices. However, its inherently low thermal conductivity and difficulties in p-type doping hinder its device performance and structural design. Heterogeneous integration has emerged as a critical technology to overcome the limitations of single materials and revolutionize device performance. This review summarizes the latest research progress in three heterogeneous integration techniques for β-Ga₂O₃∶ heteroepitaxy, mechanical exfoliation, and ion-cutting technique. The advantages and disadvantages of different integration techniques in terms of material quality, electrical and thermal properties, and device performance are comparatively analyzed. Additionally, the effects of substrate types, interfacial bonding, and interface layer thickness on heat dissipation and vertical electron transport are discussed. This review also analyzes the current challenges faced byβ-Ga₂O₃ heterogeneous integration technology and prospects its future development trends, aiming to stimulate domestic research on β-Ga₂O₃ heterogeneous integrated substrates, promote the development of β-Ga₂O₃ heterogeneous integrated devices, and accelerate the industrialization of β-Ga₂O₃ materials and devices.

Research Progress of Gallium Oxide Micro/Nano Structure-Based Detectors

CHEN Junhong, HU Jianwen, WEI Zhongming

2025, 54(3):  491-510.  doi:10.16553/j.cnki.issn1000-985x.2025.0001

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Gallium oxide (Ga₂O₃), a semiconductor material with a wide bandgap (approximately 4.9 eV) and unique optoelectronic properties, has attracted significant attention in recent years for applications in ultraviolet photodetectors (UVPD), photodetectors, and optoelectronic sensors. Ga₂O₃'s micro/nano structures, such as nanowires, nanorods, nanotubes, and nanosheets, exhibit excellent optoelectronic response characteristics, fast electron mobility, and high stability, making them crucial for enhancing the performance of detectors. This paper introduces various synthesis methods for Ga₂O₃ micro/nano structures, including hydrothermal, electrochemical deposition, and vapor deposition methods. The advantages and disadvantages of these techniques are analyzed, and how to achieve precise control over the morphology and size of Ga₂O₃ micro/nano structures by adjusting reaction conditions is discussed. Furthermore, the application of these micro/nano structures in ultraviolet photodetectors is explored, particularly their potential in high-sensitivity, high-selectivity, and polarization-sensitive optoelectronic detectors.

Investigation of Single-Event Effects of β-Ga₂O₃ Schottky Barrier Diodes with Mesa Termination

HE Song, LIU Jinyang, HAO Weibing, XU Guangwei, LONG Shibing

2025, 54(3):  511-516.  doi:10.16553/j.cnki.issn1000-985x.2024.0325

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The ultra-wide bandgap semiconductor β-Ga₂O₃, with high critical breakdown field and displacement threshold energy, show great potential for applications in harsh irradiation space environments. However, due to the low thermal conductivity and hole mobility, high-energy particle irradiation could lead to single-event burnout (SEB) far below the rated voltage. Therefore, this work proposes to transfer the peak electric field from the drift layer surface at the anode edge to the sidewall of the mesa termination, which prevents the further aggravation of electric field crowding at Schottky contact under the single-event effects (SEE). Moreover, the localized power density was reduced to increase the SEB threshold. The 1.86 GeV tantalum ions with the linear energy transfer (LET) exceeding 80 MeV·cm²·mg^-1 are adopted in our experiment. The SEB voltage of the termination-less Schottky barrier diode (SBD) is only 170 V, while the SEB threshold of SBD with mesa termination reaches 220 V. The SEE transient response of the devices was investigated by coupling electro-thermal model. The simulation results indicate that the peak electric field at the drift layer surface is significantly suppressed and the low peak electric field prevents the excessive local power dissipation to reduce the internal peak temperature of the device, and increases the SEB threshold. This work provides a new approach for the irradiation hardening method ofβ-Ga₂O₃ power devices.

Mesa Termination Technology for NiO/β-Ga₂O₃ Heterojunction Diode

WEN Junpeng, HAO Weibing, HAN Zhao, XU Guangwei, LONG Shibing

2025, 54(3):  517-523.  doi:10.16553/j.cnki.issn1000-985x.2024.0328

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The ultra-wide bandgap semiconductor β-Ga₂O₃ is a promising semiconductor material for manufacturing high power and high efficiency power device due to its high critical breakdown field and low on-state loss. However, the actual performance of existing β-Ga₂O₃ diode is far from the theoretical value. It is urgent to develop high efficiency edge termination techniques to suppress the peak electric field and improve the breakdown voltage. In this paper, the mesa termination technique for NiO/β-Ga₂O₃ heterojunction diode were systematically studied, and the performance of the devices with different etching depths were compared, including 0, 0.37, 0.74, 1.11 μm. The breakdown voltage of mesa termination diode first increases with the increase of etching depth, and then degrades due to the accumulation of the etching damage. The results show that at the etching depth of 1.11 μm, the breakdown voltage increases from 970 V to 2 600 V, and the on-state resistance slightly increases from 6.43 mΩ·cm² to 7.38 mΩ·cm². The electric field distribution of the device was studied by simulation, and it indicates that the mesa termination transfers the peak electric field from the anode edge to the etching corner, and greatly suppress the electric field. The post-annealing after etching significantly reduces the leakage current of device. The leakage current of device is only 4×10^-7 A/cm² under -2 000 V, while the breakdown voltage is not changed (2 625 V). The on-state resistance reduce to 6.96 mΩ·cm², yielding a high power figure of merit of 0.99 GW/cm². This work provides a new approach for the design of terminations for high breakdown voltage and low leakage β-Ga₂O₃ diodes.

Investigation of Boron Implanted Terminations for β-Ga₂O₃ Schottky Barrier Diodes

SHEN Rui, YU Xinxin, LI Zhonghui, CHEN Duanyang, SAI Qingling, QIAO Bing, ZHOU Likun, DONG Xin, QI Hongji, CHEN Tangsheng

2025, 54(3):  524-529.  doi:10.16553/j.cnki.issn1000-985x.2024.0287

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β-Ga₂O₃ is regarded as a promising semiconductor material for the next-generation high-power and high-efficiency power electronic devices for its exceptional physical properties such as wide bandgap and high breakdown electrical field. However, the Ga₂O₃ Schottky barrier diode (SBD) without terminations are prone to generate the peak electric fields at the edges of the Schottky electrodes, causing premature breakdown of the device, affecting its breakdown characteristics. To address this, a buried high-resistance termination achieved by selectively boron (B) ion implantation at the edge of the Schottky electrode is proposed to modulate the edge electric fields and improve the breakdown voltage. The B ions were implanted with an energy of 60 keV and a dose of 7×10¹⁴ cm^-2. The implantation depth was evaluated as approximately 200 nm by simulations. With B ion implantation, the on-state characteristics of the Ga₂O₃ SBD are not changed and the specific on-resistance is still as low as 2.5 mΩ·cm², whereas the breakdown voltage is significantly improved from 429 V to 1 402 V, which is 226% increased. The corresponding power figure of merit is improved from 74 MW/cm² to 767 MW/cm². The electric field simulations reveal that the peak electric field at the edge of the Schottky electrode is substantially suppressed with B implantation, and it decreases with the increase of the implantation depth. This work provides a new approach for the design of terminations for high-performance Ga₂O₃ power devices.