Electronic structure of the Si₆/Ge₆(111) superlattice strained to a Ge substrate

Using the total energy pseudopotential method we have calculated the electronic structure of a Si6/Ge6(111) superlattice, strained to a Ge substrate. We have also calculated the electronic structure of Si and Ge, both unstrained and strained, in the 12-atom hexagonal unit cell of the superlattice and we demonstrate how the lowest lying conduction band states at the face-centred cubic Gamma , X and L-points are dependent on strain, fold in and mix to form the superlattice states. The optical transition matrix elements of the direct transitions are considered and the valence band offset of this heterojunction is calculated