Controlling the threshold voltage of beta-Ga2O3 field-effect transistors via remote fluorine plasma treatment

Abstract

beta-phase gallium oxide (beta-Ga2O3), emerging as an ultra-wide bandgap semiconductor, suffers from negative threshold voltage (V-th) characteristics, which only allow depletion-mode (D-mode) operation; however, enhancement-mode (E-mode) operation is preferred to ensure fail-safe operation and simplify circuit topologies. Therefore, in this study, the V-th is controlled via remote fluorine plasma treatment in beta-Ga2O3 metal-insulator-semiconductor field-effect transistors (MISFETs). Under the top-gate modulation, the V-th of the fluorinated beta-Ga2O3 MISFET was positively shifted by +4 V, exhibiting a high on/off ratio (similar to 10(7)) and low su beta-threshold swing (175 mV dec(-1)). Under the double-gate modulation, the E-mode beta-Ga2O3 MISFET was demonstrated, where the V-th was estimated to be +2.2 V. The obtained results suggest that the fluorine plasma treatment is an effective method to control the V-th of the beta-Ga2O3 FETs from D-mode to E-mode, pointing out monolithic integration of beta-Ga2O3 transistors for future smart power electronics.