Indirect bandgap and band alignment for coherently strained Si(x)Ge(1-x) bulk alloys on <001> Germanium substrates.

Estimates of the fundamental (indirect) bandgap and band alignments of coherently strained Si(x)Ge(1-x) alloys for growth on Ge001> are given for x in the range 0 = x = 1. The present results were obtained by combining phenomenological deformation potential theory with the self-consistent pseudopotential results of Van de Walle and Martin [J. Vac. Sci. Technol. B3, 1256 (1985)]. It is found that the bandgap of the coherently strained alloy has a maximum value near x =0.15, where the bulk band structure changes from Ge-like to Si-like. The conduction band discontinuity, deltaE(c), shows a similar behavior, having a maximum value ~~0.10 eV at x = 0.15 and changing sign for x >~ 0.32 (i.e. Type II alignment with Ge conduction band edge lying higher in energy than the alloy conduction band edge).