Hf O ₂ and Al ₂ O ₃ gate dielectrics on GaAs grown by atomic layer deposition

High-performance metal-oxide-semiconductor field effect transistors (MOSFETs) on III-V semiconductors have long proven elusive. High-permittivity (high- κ) gate dielectrics may enable their fabrication. We have studied hafnium oxide and aluminum oxide grown on gallium arsenide by atomic layer deposition. As-deposited films are continuous and predominantly amorphous. A native oxide remains intact underneath Hf O2 during growth, while thinning occurs during Al2 O3 deposition. Hydrofluoric acid etching prior to growth minimizes the final interlayer thickness. Thermal treatments at ~600 °C decompose arsenic oxides and remove interfacial oxygen. These observations explain the improved electrical quality and increased gate stack capacitance after thermal treatments.