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 mu 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 cm(2)/(Vs) at higher gate voltages, which is a slight improvement to reported values for similar devices.

Automated summary

In this study, fully-vertical GaN FinFETs with a gate length of 550 nm were fabricated and analyzed. The devices exhibited normally-OFF behavior, with subthreshold swings close to the limit of 60 mV/dec. Low hysteresis values indicated low defect densities at the oxide/GaN interface. The devices also showed low specific ON-resistances at a maximum breakdown voltage of around 90 V, which is reasonable for the given drift layer thickness of 1 μm. Capacitance voltage measurements were used to model and identify the capacitances in the devices, and the effective and field effect mobility in the channel were approximated to be around 164 and 54 cm²/(Vs) at higher gate voltages, representing a slight improvement compared to reported values for similar devices.