Electrical characteristics of metal-oxide-semiconductor capacitors on p -GaAs using atomic layer deposition of ultrathin HfAlO gate dielectric

Properties of ultrathin HfAlO gate dielectrics on sulfur-passivated p -GaAs were investigated using capacitance-voltage and current-voltage measurement techniques and angle-resolved x-ray photoelectron spectroscopy. By optimizing the individual layer thickness of atomic-layer deposited Al₂ O ₃ and HfO₂ and the postdeposition anneal (PDA) conditions, a low equivalent oxide thickness of 1.6 nm, low gate leakage of 2.6× 10^-3 A/ cm² at V_g = V_fb -1 V, and excellent frequency dispersion characteristics were obtained. No interfacial As-O bonding and only a small amount of Ga-O bonding were detected after PDA at 500 °C. These results reveal a good quality dielectric interface on GaAs without an additional interface passivation layer.