Comparison of AlGaN/GaN Insulated Gate Heterostructure Field-Effect Transistors with Ultrathin Al_2O_3/Si_3N_4 Bilayer and Si_3N_4 Single Layer

摘要

Device performances have been compared between two types of AlGaN/GaN metal-insulator-semiconductor heterostructure field effect transistors (MIS-HFETs) with Al_2O_3/Si_3N_4 bilayers and a Si_3N_4 single layer. Al_2O_3/Si_3N_4 bilayer-based MIS-HFETs have much lower gate current leakage than Si_3N_4-based MIS devices by more than 3 orders of magnitude under reverse gate biases. An ultralow gate leakage of 1 x 10~(-11) A/mm at -15V has been achieved in the Al_2O_3/Si_3N_4 bilayer-based MIS devices though higher maximum drain-source current has been obtained in the Si_3N_4-based MIS devices. A maximum transconductance of more than 180 mS/mm with ultra-low gate leakage has been achieved in the ultrathin Al_2O_3/ Si_3N_4 bilayer-based MIS-HFET device with a gate length of 1.5 μm, which is much higher than that of less than 130 mS/mm in the Si_3N_4-based MIS devices. The reduction in the transconductance of Al_2O_3/Si_3N_4 bilayer-based devices was much smaller than that in the Si_3N_4-based MIS devices due to the employment of ultrathin bilayers with a large dielectric constant.This work demonstrates that an Al_2O_3/Si_3N_4 bilayer insulator is a superior candidate for nitride-based MIS-HFET devices.