【Domestic Papers】High-Voltage Ga₂O₃ Vertical Schottky Barrier Diode With Suspended Field Plate Assisted Shallow Mesa Termination

      Researchers from the Fuzhou University have published a dissertation titled "High-Voltage Ga₂O₃ Vertical Schottky Barrier Diode With Suspended Field Plate Assisted Shallow Mesa Termination" in ISPSD 2025.

Project Support

      This work was supported by the Natural Science Foundation of Fujian Province, China under Grant No. 2024J01252, the Science and Technology Major Project of Fujian Province, China under Grant No. 2022HZ027006, and the Fujian Province Young and Middle-aged Teacher Education Research Project under Grant No. JZ230003.

Background

      Gallium oxide (Ga₂O₃) possesses outstanding material properties, including ultra-wide bandgap of 4.5-4.9 eV, remarkable critical breakdown electric field of ~8 MV/cm, high Baliga's figure of merit (BFOM) of ~3444, high-quality substrate with low-cost potential and controllable n-type doping high-quality homoepitaxy. These excellent features make Ga₂O₃-based devices promising candidates in power switching applications. However, because Ga₂O₃ lacks effective p-type doping to date, the terminal structures widely used in Si/SiC-based devices are difficult to be applied to Ga₂O₃-based devices. Therefore, the electric field management at device edge is a difficult task for Ga₂O₃-based devices.

Abstract

      In this work, a vertical Ga₂O₃ Schottky barrier diode with suspended field plate assisted shallow mesa termination (SFPM-SBD) is proposed and fabricated. The optimized self-aligned ICP etching process, which introduces Cl₂ to facilitate the isotropic etching of Ga₂O₃, is developed to form the suspended field plate and shallow mesa termination. Owing to the effective termination, the electric field crowding phenomenon at the device edge is significantly alleviated, and thus the fabricated SFPM-SBD features a high breakdown voltage of >3.5 kV. Besides, a low specific on resistance of 5.77 mΩ·cm² can also be obtained in an Au-free process, yielding a high power figure of merit of over 2.12 GW/cm². Another advantage of the SFPM-SBD is its very simple fabrication process, which, coupled with high performances, makes the device a promising candidate for multi-kilovolts applications.

Conclusion

      In this work, a high-voltage SBD with suspended field plate and mesa termination is proposed and fabricated. By introducing Cl₂ in the ICP etching process, enhanced isotropic etching of Ga₂O₃ is realized, thereby simultaneously fabricating the suspended field plate and the mesa termination. Consequently, the SFPM-SBD features optimized electric field distributions, while maintaining the same simple process as the typical SBD with shallow mesa termination. The experimental results show that when compared with the Mesa-SBD, BV of the SFPM-SBD can significantly increase from 1.75 kV to >3.5 kV, which, together with a relatively low R_on,sp of 5.77 mΩ·cm², yields a high PFOM of over 2.12 GW/cm². This work validates the effectiveness of the SFPM terminal technology for vertical β-Ga₂O₃ power devices, and shows good prospects for the development of high-voltage Ga₂O₃ devices.