Structural, electronic, and dynamical properties of amorphous gallium arsenide: a comparison between two topological models

TL;DR

This study compares two topological models of amorphous gallium arsenide, revealing that most properties are similar despite differences in local chemical ordering, and challenges the reliance on indirect experimental evidence for certain structural defects.

Contribution

It introduces and compares two distinct topological models of amorphous GaAs, showing that most properties are unaffected by differences in local chemical ordering.

Findings

Connell-Temkin model is energetically favored over Polk.

Most properties are little affected by topology differences.

Indirect evidence for wrong bonds is weaker than previously thought.

Abstract

We present a detailed study of the effect of local chemical ordering on the structural, electronic, and dynamical properties of amorphous gallium arsenide. Using the recently-proposed ``activation-relaxation technique'' and empirical potentials, we have constructed two 216-atom tetrahedral continuous random networks with different topological properties, which were further relaxed using tight-binding molecular dynamics. The first network corresponds to the traditional, amorphous, Polk-type, network, randomly decorated with Ga and As atoms. The second is an amorphous structure with a minimum of wrong (homopolar) bonds, and therefore a minimum of odd-membered atomic rings, and thus corresponds to the Connell-Temkin model. By comparing the structural, electronic, and dynamical properties of these two models, we show that the Connell-Temkin network is energetically favored over Polk, but that most properties are little affected by the differences in topology. We conclude that most indirect experimental evidence for the presence (or absence) of wrong bonds is much weaker than previously believed and that only direct structural measurements, i.e., of such quantities as partial radial distribution functions, can provide quantitative information on these defects in a-GaAs.