Electronic and optical properties of strained and unstrained group-IV semiconductor Germanium alloys

Full text: The inherent problem of the well established Si-based semiconductor technology is the indirect nature of the fundamental band gap. However, Si/Ge can be transformed into direct semiconductors by alloying with C/Sn or by introducing strain. In this work, we focus on the electronic and optical properties of SnxGe1-x and CxGe1-x random substitutional alloys. The indirect-direct gap transition in strained and unstrained alloys as a function of the Sn/C content between 0 ≤ x ≤ 0.5 is investigated within density functional theory employing a supercell approach. Accurate alloy band structures are obtained with the modified Becke-Johnson exchange potential in combination with LDA correlation. (author)