Comparison of electrical characteristics of Schottky-gate AlGaN/GaN HEMTs using for V-based and Ti-based ohmic contacts

This study presents investigation of the electrical performance of Schottky-gate AlGaN/GaN high-electron-mobility transistors (HEMTs) incorporating a low thermal budget V/Al/Mo/Au metal stack, benchmarked against devices fabricated with a conventional (Ti/Al/Mo/Au) metallization scheme. Transfer Length Method (TLM) test structures employing the V-based metal stack, subjected to rapid thermal annealing at 700 °C, exhibited excellent linearity in current–voltage characteristics, comparable with those of Ti-based metal stack rapid thermal annealed at 880 °C. However, V-based structures revealed smoother surface morphology indicative of high-quality, low-resistance ohmic contact formation under reduced thermal budgets. Furthermore, the stability against off-bias stress of V-based and Ti-based devices was compared. It was observed that when off-bias stress increased, the on-resistance of both devices increased as expected. However, the V-based device exhibited less increase in on-resistance with increasing drain-to-source stress ( V DS,stress ), indicating a reduced degree of current collapse. To gain further insight, TCAD simulations were conducted to investigate the electric field distribution within the AlGaN/GaN HEMTs under various drain stress conditions. The results suggested that V-based devices exhibit better performance and stability due to less density of surface traps on AlGaN surface likely due to lower RTA processing temperature. Our results demonstrate that low thermal budget V-based ohmic contacts present an alternative avenue for improving stability of AlGaN/GaN HEMTs. • Schottky-gate AlGaN/GaN HEMTs using low thermal budget V-based ohmic contacts processed using rapid thermal annealing temperature at 700 °C were fabricated, characterized and compared with those reference devices using conventional Ti-based ohmic contacts processed using RTA temperature of 880 °C. • The lower thermal budget V-based ohmic contacts exhibited smoother surface morphology relative to that of the reference Ti-based ohmic contacts. Moreover, V-based and Ti-based TLM structures showed comparable I - V characteristics, contact resistance, and sheet resistance. • Both V-based and Ti-based Schottky-gate AlGaN/GaN HEMT devices exhibited nominally similar DC characteristics. However, V-based devices demonstrated higher stability against off-state bias stress. • TCAD simulations were also conducted to investigate the electric field distribution within the AlGaN/GaN HEMTs under various drain stress conditions. • Our results indicate that V-based ohmic contacts could offer an alternative avenue for improving stability of AlGaN/GaN HEMTs device against current collapse.