Origin of improved RF performance of AlGaN/GaN MOSHFETs compared to HFETs

A comparative investigation is performed of the unpassivated and the passivated heterojunction field-effect transistors (HFETs) and of the metal-oxide semiconductor HFETs (MOSHFETs) that are fabricated with identical-layer structures and fabrication technology. The influence of a `10-nm-thick silicon-dioxide layer was investigated based on an undoped AlGaN/GaN heterostructure on a SiC substrate.