Effects of high temperature annealing on the atomic layer deposited HfO₂/?-Ga₂O₃ (010) interface

Atomic layer deposited HfO2 is a primary candidate for metal–oxide–semiconductor (MOS) power devices based on the ultra-wide bandgap semiconductor ?-Ga2O3. Here, we investigated thermal stability of this stack. Out-diffusion gallium into HfO2, measured by secondary ion mass spectroscopy depth profile, was observed after annealing at 900 °C. Electrical characterization MOS capacitors (MOSCAPs) showed that diffusion caused dramatic increase in leakage current. For temperatures between 700 and 850 °C, no significant Ga observed. Nonetheless, MOSCAPs made with stacks annealed °C have significantly higher forward bias compared to as-prepared MOSCAPs. Through photo-assisted capacitance–voltage measurements (C–V), found due an interface traps (Dit) lying 0.3–0.9 eV below conduction band. We thus identified how treatments influence HfO2/Ga2O3 behavior: anneals 700–850 observe Dit leakage, while >900 results notable out-diffusion catastrophic degradation leakage. This understanding key improving performance reliability future ?-Ga2O3 devices.