Depletion-mode GaAs metal-oxide-semiconductor field-effect transistor with HfO2 dielectric and germanium interfacial passivation layer

The authors present depletion-mode n-channel GaAs metal-oxide-semiconductor field-effect transistor (MOSFET) with a TaN gate electrode, a thin HfO2 gate dielectric, and a thin germanium (Ge) interfacial passivation layer (IPL). Depletion-mode MOSFET on the molecular-beam epitaxy-grown n-type GaAs layer with an equivalent oxide thickness of 17A exhibits excellent transistor output characteristics such as a maximum transconductance of 176mS∕mm and a maximum effective electron mobility of 970cm2∕Vs. MOSFET shows a surface accumulation channel conduction above flatband condition, indicating that a high quality interface can be achieved using a Ge IPL on GaAs substrate.