Influence of Oxygen–Plasma Treatment on In-Situ SiN/AlGaN/GaN MOSHEMT with PECVD SiO(2) Gate Insulator

The influence of oxygen–plasma treatment on in situ SiN/AlGaN/GaN MOS high electron mobility transistor with SiO(2) gate insulator was investigated. Oxygen–plasma treatment was performed on in situ SiN, before SiO(2) gate insulator was deposited by plasma-enhanced chemical vapor deposition (PECVD). DC I-V characteristics were not changed by oxygen plasma treatment. However, pulsed I-V characteristics were improved, showing less dispersion compared to non-treated devices. During short-term gate bias stress, the threshold voltage shift was also smaller in a treated device than in an untreated one. X-ray photoemission spectroscopy also revealed that SiO(2) on in situ SiN with oxygen–plasma treatment has an O/Si ratio close to the theoretical value. This suggests that the oxygen plasma treatment-modified surface condition of the SiN layer is favorable to SiO(2) formation by PECVD.