Capacitance and Mobility Evaluation for Normally-Off Fully-Vertical GaN FinFETs

In this work, we present the fabrication and analysis of fully-vertical GaN FinFETs with a gate length of 550 nm. The devices with fin widths of around 100 nm reveal normally- OFF behavior and subthreshold swings (SSs) very close to the 60-mV/dec limit. Low hysteresis values indicate low defect densities at the oxide/GaN interface. The devices exhibit low specific ON-resistances at a maximum of around 90 V breakdown voltage, which is reasonable for the drift layer thickness of 1∼μ m. The capacitances in the devices were modeled and identified with capacitance voltage measurements, which could also be used to approximate the effective and field effect mobility in the channel and reveal to around 164 and 54 cm2/(Vs) at higher gate voltages, which is a slight improvement to reported values for similar devices.