Defect States Determining Dynamic Trapping-Detrapping in beta-Ga2O3 Field-Effect Transistors

Abstract

beta-Ga2O3 is an intriguing material as a channel layer for the next generation high power transistors. To assess the device level effects of the traps in beta-Ga2O3, the dynamic dispersion characteristics of a back-gated nanobelt beta-Ga2O3 field-effect transistor prepared by mechanical exfoliation from a bulk beta-Ga2O3 single crystal was investigated by the dependence of threshold voltage hysteresis on transistor transfer characteristics on the gate voltage ramp, pulsed current-voltage characteristics, and current deep level transient spectroscopy measurements. Current lag in the off-state was related to the presence of electron traps at E-c-0.75 eV, which are also present in bulk crystals and ascribed to Fe impurities or native defects. In the on-state, drain current lag was caused by surface traps with levels at E-c-(0.95-1.1) eV. Optimized passivation layers for beta-Ga2O3 are required to prevent the current collapse because the device performances are affected by the environmental molecules adsorbed on the surface. Our work can pave a way to mitigating the defect-related current collapse in beta-Ga2O3 electronic devices. (C) The Author(s) 2019. Published by ECS.