Special Quasi-ordered Structures: role of short-range order in the semiconductor alloy (GaN)$_{1-x}$(ZnO)$_x$

TL;DR

This study investigates how short-range order affects the atomic, electronic, and vibrational properties of the (GaN)$_{1-x}$(ZnO)$_x$ semiconductor alloy, revealing significant differences between ordered and disordered structures through simulations and DFT calculations.

Contribution

Introduction of the concept of Special Quasi-ordered Structure (SQoS) to represent SRO effects in semiconductor alloys and analysis of its impact on material properties.

Findings

SRO leads to stronger valence-matched nearest-neighbor pairs.

Disordered alloys show larger lattice bowing and band-gap reduction.

Lattice vibrations stabilize the disordered alloy.

Abstract

This paper studies short-range order (SRO) in the semiconductor alloy (GaN)$_{1-x}$(ZnO)$_x$. Monte Carlo simulations performed on a density functional theory (DFT)-based cluster expansion model show that the heterovalent alloys exhibit strong SRO because of the energetic preference for the valence-matched nearest-neighbor Ga-N and Zn-O pairs. To represent the SRO-related structural correlations, we introduce the concept of Special Quasi-ordered Structure (SQoS). Subsequent DFT calculations reveal dramatic influence of SRO on the atomic, electronic and vibrational properties of the (GaN)$_{1-x}$(ZnO)$_x$ alloy. Due to the enhanced statistical presence of the energetically unfavored Zn-N bonds with the strong Zn3$d$-N2$p$ repulsion, the disordered alloys exhibit much larger lattice bowing and band-gap reduction than those of the short-range ordered alloys. Inclusion of lattice vibrations stabilizes the disordered alloy.