Electronic structures calculation of Si1−xSnx compound alloy using interacting quasi-band model

We investigate energy band structures of Si
_1-x
Sn
_x
compound alloy in zincblende structure using interacting qasi-band (IQB) model. The previous IQB model has been developed for three element compound semiconductors such as A
_1-x
B
_x
D. To apply IQB for Si
_1-x
Sn
_x
, we here extend the IQB for four element compounds and calculate the electronic structures of virtual alloy as Si
_1-x
Sn
_x
Si
_1-y
Sn
_y
, where x=y. Diagonalizing a 20 × 20 non-Hermitian Hamiltonian matrix using sp3s* tight binding theory, we obtain quasi-band structures for several x. Comparing the band structures, we reveal that indirect-direct gap crossover in Si
_1-x
Sn
_x
occurs around x = 0.39.