A high thermal stability ohmic contact for GaN-based devices

Abstract

Co-integration of gallium nitride (GaN) power devices with Si logic ICs provides a way of applying high power and high efficiency circuits on a single chip. In order to co-integrate GaN devices with Si ICs, an ohmic contact for GaN devices has to be Si compatible and durable at the same or higher temperature of the back-end process in the conventional complementary metal oxide semiconductor (CMOS) industry. In this work, an Au-free ohmic junction with high thermal stability for AlGaN/GaN high electron mobility transistors (HEMTs) was presented. The proposed titanium nitride (TiN) contacts on AlGaN/GaN HEMTs retained their ohmic characteristics and stayed stable at temperatures even higher than 1000 °C. The interface chemistry analysis using STEM EELS revealed the enhancement of the binding energy of Ga-N and Al-N and invisible diffusion of Ti during treatment below 1000 °C. This clarifies the origin of the highly stable ohmic contact. Thus, our work provides a new pathway and thought for forming reliable contacts for HEMTs or another GaN-based devices.