ENERGY RELAXATION AND DEPHASING OF PHOTOEXCITED CARRIERS - MEMORY EFFECTS AND CROSS-TERMS BETWEEN DIFFERENT INTERACTIONS

On short time-scales two fundamental assumptions made in the derivation of the semiclassical Boltzmann equation become questionable: first, the concept of instantaneous collisions described by scattering rates due to Fermi's golden rule and, second, the neglect of interference terms between different interactions. We present a full quantum-kinetic description of a photoexcited carrier-phonon system and discuss the various types of approximations leading to the semiclassical case. Numerical results for the relaxation and dephasing process on different levels of approximations are given.