Multi-scale theory and simulation of direct-gap group-IV semiconductor alloys

Alloying of Ge with other group-IV elements - C, Sn or Pb - represents a promising route to realise direct-gap group-IV semiconductors for applications in Si-compatible devices, including light-emitting diodes and lasers, as well as tunnelling field-effect transistors and multi-junction solar cells. To develop a quantitative understanding of the properties and potential of group-IV alloys, we have established a multi-scale simulation framework to enable predictive analysis of their structural and electronic properties. We provide an overview of these simulation capabilities, and describe previously overlooked fundamental aspects of the electronic structure evolution and indirect- to direct-gap transition in (Si)Ge
_1-x
(C, Sn, Pb)
_x
alloys. We further describe ongoing work related to exploiting this simulation platform to compute the optical and transport properties of (Si)Ge
_1-x
Sn
_x
alloys and heterostructures.