Improved thermal stability of Al_2O_3/HfO_2/Al_2O_3 high-k gate dielectric stack on GaAs

摘要

Thermal stability of HfO_2 high-k gate dielectric on GaAs is investigated. Compared to HfO_2 gate dielectric, significant improvements in interfacial properties as well as electrical characteristics were found by constructing a Al_2O_3/HfO_2/Al_2O_3 dielectric stack. At elevated temperatures, the amorphous Al_2O_3 layers were effective in inhibiting crystallization of HfO_2. Since the passivating Al_2O_3 layers prevent interfacial oxide and trap charge formation, it aids in reducing the increasing rate of equivalent oxide thickness as well as capacitance-voltage hysteresis. Transmission electron microscopy and x-ray photoelectron spectroscopy data supported the improved electrical characteristic of GaAs metal-oxide-semiconductor capacitors with Al_2O_3/HfO_2/Al_2O_3 gate dielectric stack.