AlGaN/GaN MISHEMTs with epitaxially grown GdScO3 as high- κ dielectric

Abstract

Epitaxially grown GdScO₃ was integrated in a GaN-based metal-insulator-semiconductor high electron mobility transistor as a high-κ gate passivation layer. Microstructural investigations using transmission electron microscopy and x-ray diffraction confirm the epitaxial growth of GdScO₃ on GaN deposited by pulsed laser deposition on the AlGaN-GaN heterostructure. The metal-insulator-semiconductor high electron mobility transistor was compared to unpassivated and to Al₂O₃ passivated high electron mobility transistors. A layer of 20 nm GdScO₃ reduces the gate leakage current below the level of the Al₂O₃ passivated transistors and below the off-current of the high electron mobility transistor without any gate dielectric. Time-dependent measurements show a strong dependence of the drain leakage current in the off-state on light illumination, which indicates slow trapping effects in GdScO₃ or at the GdScO₃–GaN interface.