Enhanced leakage current properties of HfO2/GaN gate dielectric stack by introducing an ultrathin buffer layer

Abstract

The band alignments of HfO2/GaN, HfO2/SiO2/GaN and HfO2/Al2O3/GaN gate dielectric stacks were comparatively investigated by using X-ray photoelectron spectroscopy. It was observed that the introduction of an ultrathin buffer layer film (SiO2 or Al2O3) in HfO2/GaN stack can make the band alignments more symmetrical with larger barrier height as identified by the valence band offsets and electron energy loss spectrum measurements. At room temperature, the leakage current density as function of temperature is 4.1 × 10−6, 3 × 10−7 and 9.8 × 10−8 A cm−2 at the bias of 1 V for the HfO2/GaN, HfO2/Al2O3/GaN and HfO2/SiO2/GaN gate dielectric stacks, correspondingly. With temperature increase from room temperature to 300 °C, the HfO2/SiO2/GaN gate dielectric stack exhibits lowest lower leakage current density than that of others. The HfO2/GaN high-k gate dielectric stack with an ultrathin SiO2 buffer layer appears to be a promising candidate for future GaN based high temperature metal-oxide-semiconductor (MOS) devices applications.