Process dependency on threshold voltage of GaN MOSFET on AlGaN/GaN heterostructure

•GaN MOSFETs with recessed gate on AlGaN/GaN heterostructure were fabricated and evaluated.•The devices with silane-based oxide have higher channel mobility and lower interface state density than that of TEOS.•It is found that positive charges of around 1×1012q/cm2 exist near the interface at just threshold condition.•The main reason for the negative threshold should be the dry etching damages.