First-principles electronic-structure calculation of dangling bonds at Si/SiO$_2$ and Ge/GeO$_2$ interfaces

TL;DR

This study uses first-principles calculations to compare dangling bonds at Si/SiO2 and Ge/GeO2 interfaces, revealing significant differences in their electronic structures and charge distributions, which explain experimental observations.

Contribution

It provides a detailed first-principles analysis of dangling bonds at Ge/GeO2 interfaces, highlighting differences from Si/SiO2 and explaining the absence of ESR signals for Ge dangling bonds.

Findings

Ge-DB states do not appear in the energy band gap of Ge/GeO2

Charge density of Ge-DB spreads more widely than Si-DB

Differences explained by metallic bonding and lattice mismatch effects

Abstract

Evidence of the absence of the clear electron spin-resonance signal from Ge dangling bonds (DBs) at Ge/GeO$_2$ interfaces is explored by means of first-principles electronic-structure calculations. Comparing the electronic structures of the DBs at Si/SiO$_2$ and Ge/GeO$_2$ interfaces, we found that the electronic structure of the Ge-DB is markedly different from that of the Si-DB; the Ge-DB states does not position in the energy band gap of the Ge/GeO$_2$ interface while the Si-DB states clearly appears. In addition, the charge density distribution of the Ge-DB state spreads more widely than that of the Si-DB state. These features are explained by considering the metallic properties of the bonding network of the Ge/GeO$_2$ interface and the structural deformation of the Ge bulk at the Ge/GeO$_2$ interface due to the lattice-constant mismatch.