Band structure and optical absorption of strained Si1−x−yGexCy alloys: a Tight-Binding approach

In this paper, the computation of the band structure and critical energy transition points of ternary random alloys is discussed within the Virtual Crystal Approximation (VCA) in a Tight-Binding (TB) framework. An improved VCA model for Si
1−x−y
Ge
x
C
y
(hereafter referred as SiGeC) is presented, which accurately describes the main energy transitions and shows good agreement with random crystal supercell calculations. Following [1], these transition energies are used to infer the variation of the SiGeC optical absorption in the Near and Short-Wavelength Infrared (resp. NIR and SWIR) as a function of composition and strain. Our model provides a physical-based tool for materials screening for opto-electronics application. Finally the optical parameters are used to simulate and predict the optical absorption of SiGeC resonant cavities.