Our work has been published in IEEE EDL 2022!

Happy New Year!

Our work which was done in my PhD at Kyoto University has published in IEEE EDL 2022! The paper title is "Breakdown Electric Field of GaN p+-n and p-n+ Junction Diodes with Various Doping Concentrations". In this paper, we studied avalanche breakdown characteristics in GaN p-n junction diodes with various epitaxial structures (different conduction types (p- or n-types), different doping concentrations). Owing to developed etching technology to form the vertical mesa edge termination and smooth mesa side wall, we demonstrated stable avalanche breakdown. Based on the elaborate characterization of space charge concentrations, the breakdown electric fields of the fabricated devices were obtained. These values showed excellent agreement with the ideal critical electric field of GaN, which was calculated by the impact ionization coefficients of GaN (reported in T. Maeda et al., J. Appl. Phys. 129, 185702 (2021). and IEDM 2021.).

In the paper, ideal avalanche breakdown in GaN p-n+ junction diodes (low doped p-type drift layer) was achieved for the first time. The avalanche breakdown in p-GaN is almost the same with that in n-GaN (strictly speaking, the breakdown voltage in p-GaN is expected to be approximately 5% lower than that in n-GaN, due to the smaller electron impact ionization coefficient in GaN). These results are useful to understand impact ionization and avalanche phenomena in GaN (especially, considering breakdown in power devices with low doped p-GaN such as GaN superjunction MOSFETs.).

If you are interested in this work, please access to T. Maeda et al., IEEE Electron Devices Letters, 43(1), 96-99 (2022)!

I would like to express my sincere gratitude to my supervisors, collaborators and colleagues. Thanks!

Takuya Maeda (January 5th, 2022)