β-phase gallium oxide (β-Ga2O3), emerging as an ultra-wide bandgap semiconductor, suffers from negative threshold voltage (Vth) 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 Vth is controlled via remote fluorine plasma treatment in β-Ga2O3 metal-insulator-semiconductor field-effect transistors (MISFETs). Under the top-gate modulation, the Vth of the fluorinated β-Ga2O3 MISFET was positively shifted by +4 V, exhibiting a high on/off ratio (∼107) and low sub-threshold swing (175 mV dec-1). Under the double-gate modulation, the E-mode β-Ga2O3 MISFET was demonstrated, where the Vth was estimated to be +2.2 V. The obtained results suggest that the fluorine plasma treatment is an effective method to control the Vth of the β-Ga2O3 FETs from D-mode to E-mode, pointing out monolithic integration of β-Ga2O3 transistors for future smart power electronics.
ASJC Scopus subject areas
- Materials Chemistry