Ultrafast Coherent and Incoherent Dynamics in Photoexcited Semiconductors

Abstract

Present-day technology allows the investigation of relaxation and dephasing phenomena in semiconductors with a time resolution which has now reached a few femtoseconds (Shah, 1989; Kurz, 1992). On such a time-scale, coherent aspects play an important role and the carrier dynamics cannot be treated in terms of the traditional semiclassical transport theory. Therefore, the ultrafast dynamics in a photoexcited semiconductor is usually described in terms of the Semiconductor Bloch Equations (SBE). Our solution of this coupled set of quantum kinetic equations is based on a decomposition of such equations in a coherent and an incoherent part. The former is integrated directly while the latter is solved by means of a generalized Monte Carlo (MC) technique. In addition to a simulation of the various distribution functions, this will result in a simulation of the interband polarization induced by the coherent light field.