Superior Suppression of Gate Current Leakage in AI_2O_3/Si_3N_4 Bilayer-Based AIGaN/GaN Insulated Gate Heterostructure Field-Effect Transistors

摘要

AlGaN/GaN-based metal-insulator-semiconductor heterostructure field-effect transistors(MIS-HFETs)with Al_2O_3/Si_3N_4 bilayer as insulator have been investigated in detail,and compared with the conventional HFET and Si_3N_4-based MIS-HFET devices.Al_2O_3/Si_3N_4 bilayer-based MIS-HFETs exhibited much lower gate current leakage than conventional HFET and Si_3N_4-based MIS devices under reverse gate bias,and leakage as low as 1 X 10~(-11)A/mm at-15 V has been achieved in Al_2O_3/Si_3N_4-based MIS devices.By using ultra-thin Al_2O_3/Si_3N_4 bilayer,very high maximum transconductance of more than 180 mS/mm with ultra-low gate leakage has been obtained in the MIS-HFET device with gate length of 1.5 mum,a reduction less than 5% in maximum transconductance compared with the conventional HFET device.This value was much smaller than the more than 30% reduction in the Si_3N_4-based MIS device,due to the employment of ultra-thin bilayer with large dielectric constant and the large conduction band offset between Al_2O_3 and nitrides.This work demonstrates that Al_2O_3/Si_3N_4 bilayer insulator is a superior candidate for nitrides-based MIS-HFET devices.