Evaluation of AlGaN/GaN‐HFET with HfAlO gate insulator

Abstract

AbstractMetal‐insulator‐semiconductor (MIS) heterostructure field‐effect transistors (HFETs) fabricated with HfAlO as a gate insulator with high dielectric permittivity are demonstrated to achieve true enhancement‐mode operation with no gate leakage and high drain current density. Insertion of the HfAlO layer allows for forward gate bias voltages of up to +8 V without gate leakage (maximum gate current density of 1.2×10–5 mA/mm at +8 V gate bias) under direct current operation. Utilizing the extended forward gate bias swing, a maximum drain current density of 767 mA/mm is achieved, substantially higher than that of the non‐insulated HFET (427 mA/mm). A recessed‐gate MIS‐HFET with the HfAlO gate insulator exhibits a threshold voltage of +2.0 V and zero transconductance below a gate bias of +0.9 V, demonstrating true enhancement‐mode operation for the first time in recessed‐gate AlGaN/GaN‐HFETs with a maximum drain current density of 253 mA/mm at +5 V (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)