Surface passivation properties of atomic-layer deposited hafnium oxide on a (100) β-Ga2O3 MOSFET

Abstract

We report the effect of HfO2 passivation on the electrical characteristics of (100) β-Ga2O3 metal-oxide-semiconductor field-effect transistors (MOSFETs). The atomic-layer-deposited HfO2 layer with negative defect charges enhances the transconductance and subthreshold slope. A significant positive threshold voltage (V TH) shift of ∼32 V is induced after the passivation. Moreover, significantly less V TH shift of ∼2 V is observed under negative bias stress (NBS) for 3600 s in comparison with an Al2O3 passivated and unpassivated device. Physics-based technology computer aided design (TCAD) simulation is performed to demonstrate the surface depletion effect and the dependency on the density of negative fixed charges in the HfO2 passivation layer. Finally, the HfO2 passivated device maintains superior electrical characteristics compared to the unpassivated device at a temperature of up to 500 K.