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

摘要

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