High Integrity SiO2 Gate Insulator Formed by Microwave-Excited Plasma Enhanced Chemical Vapor Deposition for AlGaN/GaN Hybrid Metal–Oxide–Semiconductor Heterojunction Field-Effect Transistor on Si Substrate

High quality SiO2 gate insulator has been demonstrated for GaN metal–oxide–semiconductor (MOS) transistor which has high performance with normally-off operation. The SiO2 films formed on GaN by microwave-excited plasma enhanced chemical vapor deposition (MW-PECVD) and annealed after deposition exhibits a low-interface state density between SiO2 and GaN, a high-breakdown field, and a high charge-to-breakdown. The SiO2 films have been also applied to the gate insulator of AlGaN/GaN hybrid MOS heterojunction field-effect transistor (HFET) on Si substrate. The MOS-HFET show excellent properties with the threshold voltage of 4.2 V and the maximum field-effect mobility of 161 cm2 V-1 s-1.