DC and RF Characteristics in Al2O3/Si3N4 Insulated-Gate AlGaN/GaN Heterostructure Field-Effect Transistors

Abstract

Al2O3/Si3N4 insulated-gate AlGaN/GaN heterostructure field-effect transistors (HFETs) have been fabricated, where excellent RF characteristics have been obtained in addition to the low gate leakage current as the result of employing the metal–insulator–semiconductor (MIS) structure. In an HFET with a gate length (Lg) of 0.1 µm, the cutoff frequency ( fT) and maximum oscillation frequency ( fmax) were estimated to be 70 and 90 GHz, respectively. The drain current density (Id) and transconductance (gm) were 1.30 A/mm and 293 mS/mm, respectively. The gate leakage current (Ig) was as low as 4×10-5 A/mm even at a forward bias voltage of +3 V.