Orientation-dependent structural and electronic properties of Ge/a-GeO2 interfaces: first-principles study

Abstract

While the properties of the non-(100) Ge surface become more important with the scaling down of Ge-based transistor devices, the stability and electronic properties of the interface between non-(100) Ge and amorphous GeO2 (a-GeO2) compared to those of Ge(100) and a-GeO2 are still not well known. In this study, first-principles calculations were performed to systematically study the atomic and electronic structures of Ge/a-GeO2 interfaces with various surface orientations of Ge. The study shows that the Ge(111)/a-GeO2 and Ge(100)/a-GeO2 interfaces have the lowest and highest interface energies, respectively. The stability of the Ge/a-GeO2 interface is governed by the interfacial bond density and the minimization of the dangling bonds. We find that the interface region, composed of the Ge suboxides, dominates the electronic structures of the Ge/a-GeO2. The Ge atoms with uncompensated dangling bonds result in various trap states within the band gap of Ge, which is related to the charge neutrality level of the Ge defect. The band offsets between Ge and a-GeO2 show little dependence on the original Ge orientation.