【Member Papers】1.5-kV Blocking Vertical AgOₓ/β-Ga₂O₃ Schottky Barrier Diodes with Ultralow Leakage Current and Over 1013 Rectification Ratio

      Researchers from the Xidian University and Suzhou Institute of Nano-Tech and Nano-Bionics, CAS have published a dissertation titled "1.5-kV Blocking Vertical AgO_x/β-Ga₂O₃ Schottky Barrier Diodes with Ultralow Leakage Current and Over 10¹³ Rectification Ratio " in Journal of Physics D: Applied Physics.

Project Support

      The research was supported by the National Natural Science Foundation of China (Grant Nos. 62293522, 62204255, and 62234007) and the Key Program of Shaanxi Provincial Department of Science and Technology Support (2024CY2-GJHX-81).

Background

      β-phase gallium oxide (β-Ga₂O₃) has garnered significant interest for high-power electronic applications due to its ultra-wide bandgap, high critical field strength, controllable doping, and the availability of large-diameter wafers. Among β-Ga₂O₃ device architectures, vertical Schottky barrier diodes (SBDs) are preferred for high-voltage and high-current applications since they enable current scaling. Over the past decade, substantial progress has pushed device performance toward the material limit through various edge terminations, including field plates, mesa termination, implanted edge termination, and junction termination extension; to date, numerous β-Ga₂O₃ SBDs with breakdown voltage (V_br) > 2 kV have been reported.

      Schottky contacts that combine a high Schottky barrier height (SBH) with low reverse leakage currents are essential for making high-voltage β-Ga₂O₃ SBDs. Prior work has focused on oxidized noble metals, surface treatments, and ultrathin dielectric interlayers. Oxidized noble metals such as PtO_x, IrO_x, and RuO₂ can substantially raise SBH owing to their higher work function relative to the base metals. Silver oxide (AgO_x) is particularly attractive owing to lower material cost of Ag, the highest reported SBHs on β-Ga₂O₃, and simple fabrication methods including thermal oxidation, pulsed laser deposition, and radio-frequency (RF) magnetron sputtering. AgO_x exhibits multiple phases, such as AgO, Ag₂O, Ag₂O₃, Ag₄O₃, and Ag₄O₄. Among these, Ag₂O is the most thermodynamically stable, with a decomposition threshold of approximately 300 ℃. Nevertheless, AgO_x as a high-barrier anode for β-Ga₂O₃ SBDs remains underexplored.

Abstract

      High-performance vertical AgO_x/β-Ga₂O₃ Schottky barrier diodes (SBDs) were demonstrated in this work. Ag₂O was confirmed as the primary phase in the AgO_x films deposited by RF magnetron sputtering at room temperature, using the X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The built-in voltage (V_bi) was determined to be 2.3 V, corresponding to a Schottky barrier height of 2.41 eV at the AgO_x/β-Ga₂O₃ interface. The vertical AgO_x/β-Ga₂O₃ SBDs achieved an ultralow leakage current of <10^-11 A/cm² with a rectification ratio over 10¹³ and a low differential specific on-resistance (R_ON,sp) of 5 mΩ·cm². A high reverse breakdown voltage (V_br) of 1.5 kV was obtained, resulting in a decent power figure of merit (V_br²/R_ON,sp) of 0.46 GW/cm². These results highlight a promising pathway for developing high-performance β-Ga₂O₃-based power diodes.

Conclusion

      In conclusion, the AgO_x film as anode electrode was successfully deposited on β-Ga₂O₃ using RF magnetron sputtering at room temperature, demonstrating high crystalline quality using XPS and XRD. Due to the high crystalline quality of the AgO_x film and large SBH at the AgO_x/β-Ga₂O₃ interface, the fabricated AgO_x/β-Ga₂O₃ SBDs achieve an excellent performance including reduced leakage current less than 10^-11 A/cm² and enhanced breakdown voltage exceeding 1.5 kV. Combined with the high On-state current over 10² A/cm² and a differential R_ON,sp of 5 mΩ·cm², yielding a remarkable I_ON/I_OFF exceeding 10¹³ and PFOM reaching 0.46 GW/cm². As compared to the reported results without the edge termination, the device exhibits the highest I_ON/I_OFF and lowest J_OFF with a decent V_br. These results underscore the promise of AgO_x as a high-barrier contact for next-generation β-Ga₂O₃-based power rectifiers.