Abstract:
In non-crystalline semiconductors, the disorder in the valence and conduction bands is statistically correlated. This leads on average to an effective kinematical correlation between the electron and holes resembling the exciton phenomena, as is well known for linear optical response. We study this correlation employing non-equilibrium Green's functions for non-linear transients induced in semiconductor alloys by short strong optical pulses. The exciton analogy is incomplete, as the electron and hole states are mixed by light, but the notion of an effective final state interaction is valid. Numerical solution employing a self-consistent single-site approximation is used to analyze the onset and a ripe stage of disorder-related e-h coupling and mixing, and their influence on the transient polarization and energy transfer, whose late stages depend strongly on the degree and character of the band-band disorder correlation. Finally, we obtain the linear response limit and link the correlation vertex with the effective Elliott factor.