The energy band gaps and substitutional deep impurity levels of metastable alloys ${\mathrm{Ge}}_{\mathrm{x}}$${\mathrm{Sn}}_{1\mathrm{-}\mathrm{x}}$ are predicted. As a function of decreasing alloy composition x the indirect band structure of semiconducting Ge first becomes direct (indicating that ${\mathrm{Ge}}_{\mathrm{x}}$${\mathrm{Sn}}_{1\mathrm{-}\mathrm{x}}$ may have applications as an infrared detector) and then metallic. Doping anomalies commonly occur as x decreases. Between x≃0.4 and x≃0.8, the Gunn effect should occur.

• Received 21 May 1987

DOI:https://doi.org/10.1103/PhysRevB.36.7994