A Novel Thin Al 2 O 3 Gate Dielectric by ECR‐Plasma Oxidation of Al for AlGaN/GaN Insulated Gate Heterostructure Field‐Effect Transistors

A novel formation process of a thin Al2O3 gate dielectric for AlGaN/GaN insulated gate (IG) heterostructure field-effect transistors (HFETs) is presented. Al2O3 was formed in an ultrahigh vacuum environment by a process sequence consisting of deposition of a thin Al film on the surface of the AlGaN/GaN heterostructure wafer, its ECR-O2 plasma oxidation and subsequent annealing. Its composition was confirmed by in-situ X-ray photoelectron spectroscopy measurements. Fabricated ring-shaped IG-HFET test devices exhibited good gate control of two-dimensional electron gas (2DEG). Forward and reverse gate leakage currents were very much reduced in IG-HFETs, being smaller than those of Ni Schottky gate HFETs by five to seven orders of magnitude. The new gate structure seems to be extremely promising for realizing high performance AlGaN/GaN HFETs.