Impact of thermal oxidation pressure and temperature on deactivation of the interfacial trap states in Al₂O₃/GaAs MOS capacitor

Abstract

Although GaAs is one of the most attractive channel materials for achieving high electron mobility, reduction of the interface state is still required for high quality MOS devices. In this paper, thermal oxidation under two pressures and various temperatures, and subsequent HF etching were performed to deactivate the interfacial states of the Al 2 O 3 /GaAs stack. High pressure oxidation (HPO) at 10 atm and 400 8C resulted in substantial improvement in the C-V frequency dispersion characteristics whereas the deactivation effect of the interfacial trap density under the thermal oxidations at 1 atm was not observed irrespective of the thermal oxidation temperature, ranging from 400 to 550 8C. Strong disparity between pressure and temperature was elucidated based on the existence of an efficient As excess layer and the prevention of unwanted Ga oxidation.

Interfacial and Electrical Properties of GaAs Metal-Oxide-Semiconductor Capacitor with ZrAlON as the Interfacial Passivation Layer

“…[4] However, the high-𝑘/GaAs interface usually has many defects, e.g., Ga-/As-oxides and As-As dimers, which will result in the Fermi level pinning on the GaAs surface. [1,5,6] Thus it is extremely important to passivate the interface by using an interfacial passivation layer (IPL) before depositing the high-𝑘 gate dielectric. Usually, aluminum-oxide (Al 2 O 3 ) is regarded as a desirable gate dielectric because of its large bandgap (∼9 eV), high breakdown field (∼5-10 MV/cm), high thermal stability and remaining amorphous under typical processing conditions.…”