[TuP3C] Power Devices

[TuP3C-09] Inversion-type GaN MOSFETs Fabricated by Applying Long-term 300°C Annealing Simultaneously to MOS Interfaces and Ohmic Contacts

〇Hiroto Akabane¹, Hinata Karasawa¹, Masanobu Takahashi¹, Masamichi Akazawa¹ (1. Hokkaido University (Japan))

GaN MOSFETs are promising candidates for high-efficiency power applications. To obtain highly efficient MOSFETs, the process conditions must be carefully designed so as not to deteriorate the MOS interface quality. In this work, inversion-type GaN MOSFETs were fabricated by applying 300^oC postmetallization annealing simultaneously to both MOS interfaces and ohmic contacts to reduce the interface state density and contact resistance at the end of fabrication process. The fabricated MOSFET was a circular fat-gate MOSFET with a channel length of 80 μm, so that the gradual channel approximation was applied to device characterization. The completed MOSFET exhibited output characteristics with good saturation characteristics. On the basis of the transfer characteristics, the subthreshold swing was determined to be 75 mV/decade, and the effective channel mobility determined using the gradual channel approximation equation for ring-gate MOSFETs was 140 cm²/V/s. An extremely low interface state density near the conduction band at the Al₂O₃/GaN interface was highly likely achieved in fabricated MOSFETs.