Perfect short-range ordered alloy with line-compound-like properties in the ZnSnN2:ZnO system
Jie Pan, Jacob Cordell, Garritt J. Tucker, Andriy Zakutayev, Adele C. Tamboli, Stephan Lany
Abstract
Abstract We present a new solid-state material phase which is a disordered solid solution but offers many ordered line-compound features. The emergent physical phenomena are rooted in the perfect short-range order which conserves the local octet rule. We model the dual-sublattice-mixed semiconductor alloy $${\mathrm{(ZnSnN}}_{\mathrm{2}}{\mathrm{)}}_{1 - x}{\mathrm{(ZnO)}}_{2x}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>(ZnSnN</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>2</mml:mi> </mml:mrow> </mml:msub> <mml:msub> <mml:mrow> <mml:mi>)</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>1</mml:mn> <mml:mo>−</mml:mo> <mml:mi>x</mml:mi> </mml:mrow> </mml:msub> <mml:msub> <mml:mrow> <mml:mi>(ZnO)</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> <mml:mi>x</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> using first-principles calculations, Monte-Carlo simulations with a model Hamiltonian, and an extension of the regular solution model by incorporating short-range order. We demonstrate that this unique solid solution, occurring at a “magic” composition, can provide an electronically pristine character without disorder-induced charge localization and, therefore, a superior carrier transport similar to ordered phases. Interestingly, this phase shows singularities that are absent in the conventional solid-solution models, such as the regular solution and band-gap bowing model. Thermodynamically, this alloy phase has a sharply reduced enthalpy at its composition (like a line compound), but it still requires the entropy from long-range disorder to be stabilized at experimentally accessible temperatures.