Electronic structure of Si1−x−yCxGey

The pseudopotential method associated with the improved virtual crystal approximation (VCA) is used to calculate the electronic band structure and density of states of Si1−x−yCxGey alloys. We find that the addition of carbon to the SiGe alloy lowers the gap. We also show that the improved VCA exhibits the true bowing of the band gap. Results show also the behaviour of the valence band width versus carbon concentration which increases as carbon concentration increases.