AlGaN/GaN Heterostructure Field Effect Transistors (HFETs) are considered as ideal candidates for high power and high frequency applications. Insulated-gate HFET structures using PECVD SiO2 have been demonstrated to have enhanced reliability as compared to their schottky counterparts. However, the presence of SiO2 under the gate brings in problems like device threshold voltage dispersion leading to non-linearity, if the quality of the oxide is not good.

This dissertation reports on a novel digital oxide deposition (DOD) technique using PECVD for depositing high quality insulating SiO2 films with negligible oxide and interface charges to fabricate MOSHFET devices with negligible threshold voltage dispersion and high reliability simultaneously. The combination of high quality SiO2 films and improved fabrication process has resulted in RF powers as high as 16 W/mm at 2GHz with stability of >100 hours on field-plated MOSHFETs.