Analytical charge control model for AlGaN/GaN MIS-HFETs including an undepleted barrier layer

An analytical charge control model considering the insulator/AlGaN interface charge and undepleted Al-GaN barrier layer is presented for AlGaN/GaN metal-insulator-semiconductor heterostructure field effect transistors （MIS-HFETs） over the entire operation range of gate voltage.The whole process of charge control is analyzed in detail and partitioned into four regions：Ⅰ—full depletion,Ⅱ—partial depletion,Ⅲ—neutral region andⅣ—electron accumulation at the insulator/AlGaN interface.The results show that two-dimensional electron gas（2DEG） saturates at the boundary of regionⅡ/Ⅲand the gate voltage should not exceed the 2DEG saturation voltage in order to keep the channel in control.In addition,the span of regionⅡaccounts for about 50%of the range of gate voltage before 2DEG saturates.The good agreement of the calculated transfer characteristic with the measured data confirms the validity of the proposed model.