Band structure and instability of Ge1−xSnx alloys

Abstract Self-consistent ab initio pseudopotential calculations for Ge1−xSnx alloys in the Virtual Crystal Approximation (VCA) and for zincblende (zb-) GeSn clearly show their instability against phase segregation at zero temperature. The GeSn bond is studied and compared to SiC and SiGe. The non-relativistic LDA band structures of VCAGe.5Sn.5 and zbGeSn are presented and show strong similarity. The resulting energy gaps for all χ are corrected empirically and prove the existence of a “direct gap window” for .26 ≤ χ ≤ .74, with a maximum energy gap of 0.61eV which gradually decreases to zero at χ = .74.

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