Nonisovalent Si-III-V and Si-II-VI alloys: Covalent, ionic, and mixed phases

Nonequilibrium growth of Si-III-V or Si-II-VI alloys is a promising approach to obtaining optically more active Si-based materials. We propose a new class of nonisovalent $\mathrm{S}{\mathrm{i}}_{2}\mathrm{AlP}$ (or $\mathrm{S}{\mathrm{i}}_{2}\mathrm{ZnS}$) alloys in which the Al-P (or Zn-S) atomic chains are as densely packed as possible in the host Si matrix. As a hybrid of the lattice-matched parent phases, $\mathrm{S}{\mathrm{i}}_{2}\mathrm{AlP}$ (or $\mathrm{S}{\mathrm{i}}_{2}\mathrm{ZnS}$) provides an ideal material system with tunable local chemical orders around Si atoms within the same composition and structural motif. Here, using first-principles hybrid functional calculations, we discuss how the local chemical orders affect the electronic and optical properties of the nonisovalent alloys.

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