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

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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.

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URL

https://arxiv.org/abs/1505.06329

PDF

https://arxiv.org/pdf/1505.06329