STUDY ON THE REDUCTION OF ACCESS RESISTANCE OF INAIN/GAN HIGH ELECTRON MOBILITY TRANSISTORS

Abstract

In this work the reduction of access resistance in InAlN/GaN HEMTs was focused. The gold-free Hf/Al/Ta contacts were realized on InAlN/GaN with low contact resistance and low thermal budget. The carrier transport mechanism was also studied for the Hf-based contacts on InAlN/GaN. Compared to the traditional Ti/Al/Ni/Au contacts, the surface roughness and interface between metal and semiconductor were found to be improved for Hf/Al/Ta contacts. With comparable DC output and transfer characteristics to the devices with Ti/Al/Ni/Au contacts, the three-terminal off-state breakdown voltage of InAlN/GaN HEMTs with Hf/Al/Ta contacts was enhanced significantly by ~ 53.5 %. To further reduce the access resistance, LaAlO3 passivation was also examined in InAlN/GaN HEMTs. The results indicated that LaAlO3 passivation can reduce sheet resistance of InAlN/GaN at access region, suppress current collapse and increase maximum drain current and maximum transconductance obviously.