Impact of Interfacial Oxygen Content on Bonding, Stability, Band Offsets, and Interface States of GaAs:HfO2 Interfaces

Abstract

A theoretical study of the structural and electronic properties of GaAs:HfO2 interface is performed using the density functional theory method. For the interfaces with Ga−O bonds (formed between Ga-terminated GaAs surface and O-terminated HfO2 surface), we found that the interfaces with 10% and 20% interfacial oxygen removed are thermodynamically stable over a wide range of O chemical potential. By gradually decreasing the interfacial O content from 100% to 30% (by changing O chemical potential corresponding to varying the growth condition), the valence band offset increases from 1.06 to 3.34 eV. The analysis of the electronic structures indicates that for interfaces with high interfacial oxygen content, the interface gap states are induced by interfacial Ga dangling bonds and As−As dimer pairs, which are formed by interface atomic structure reconstruction. The decreasing interfacial oxygen content causes the decrease of the charge states of interfacial Hf and Ga leading to metallic interface states. For interfaces with low interfacial oxygen content, we found that As−As, Ga−Ga dimer pairs, and Ga and As dangling bonds are also formed and contribute to the interface gap states.