The role of ultrafast intercarrier processes in sub-picosecond laser studies of semiconductors

Abstract

The authors present an attempted consistent description of the interplay of coherent and incoherent electronic processes during the transient non-linear optical response of a laser-pulse-excited electron-hole plasma in a semiconductor. By applying the density-matrix formalism of Stahl's 'coherent band-edge dynamics' they follow the evolution of the carrier system, going all the way back to the instant of the photogeneration of the individual electron-hole pairs. The basic objects of the theory are expectation values of the various carrier-carrier pair correlation functions in r space. Their time evolution is given by Bloch-type rate equations with phenomenological time-dependent damping terms, which in turn are obtained from a parallel r-space ensemble Monte Carlo simulation of the detailed scattering dynamics of the non-equilibrium carrier-phonon system. They apply this novel algorithm to experimental scenarios recently realized in the sub-picosecond laser-pulse spectroscopy of hot carriers in GaAs-type polar semiconductors.