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Seminario
"Electronic structure of Ge_{1-x-y} Si_{x} Sn_{y} ternary alloys. "

Relatore: Dr.ssa Cecilia I. Ventura- Centro Aṭmico Bariloche and Universidad Nacional de Rio Negro, Bariloche, Argentina

Aula Maxwell
18 Settembre 2012 ore 11.30

Abstract
Ternary group-IV alloys have a wide potential for applications in optoelectronics, and multi-junction high-efficiency solar cells: they can be lattice-matched to GaAs, Ge and Si substrates, having bandgaps complementary to III-V semiconductors. Ge_{1-x-y}Sn_{x}Si_{y} alloys exhibit full decoupling of lattice and bandstructure, and a concentration-tunable bandgap. Nevertheless, no direct measurements of the fundamental gap or bandstructure calculations are available, yet. We report a first calculation of the electronic structure of Ge_{1-x-y}Sn_{x}Si_{y} ternary alloys, using tight-binding orbitals suitable for group IV elements and the virtual crystal approximation. Our results confirm predictions and experimental indications that a 1 eV bandgap is attainable with these ternary alloys, as required for the next-generation of high-efficiency multi-junction solar cells for satellites. \keywords{Semiconductor alloys,electronic structure,multijunction solar cells}