Evanescent states in thin silicon films and their significance

Abstract

The full-zone $\mathbf{k}\ensuremath{\cdot}\mathbf{p}$ method is used along with the effective-mass and envelope-function approximations to investigate the photoluminescence (PL) behavior of free-standing thin silicon films. The formulation reveals that blue and red PL bands coexist and that the blue band is due to the transition from a high evanescent state to a heavy-hole state. The square of the transition momentum is such that the blue band decays fast whereas the red decays slowly. The presence of the high evanescent state explains why the blue PL can be observed in relatively thick silicon films.