Qualitative prediction of conduction band valley profile in silicon thin films from bulk properties by density functional k · p perturbation theory

To obtain the properties of the conduction band valley in silicon thin films from information on the bulk, we calculate the band energy derivatives by the density functional k • p perturbation theory [C. J. Pickard and M. C. Payne, Phys. Rev. B 62, 4383 (2000)]. It is demonstrated that the derivatives obtained by the k.p method through direct integration of the matrix elements agree well with those obtained by numerical differentiation up to the fourth order both for the norm-conserved and ultrasoft pseudopotentials. The effective mass and displacement of the conduction band bottom in thin films, which determines effective mass anomalies in the confined system, are qualitatively well predicted by the combination of the effective mass theory and the bulk band derivatives.