Green's function description of momentum-orientation relaxationof photoexcited electron plasmas in semiconductors

We present numerical results for the momentum-orientation relaxation of optically excited electron plasmas in bulk semiconductors. Our results are based on the full two-time Green's function approach for carrier-carrier scattering and are compared to the results obtained within the conventional quantum Boltzmann equation. Defining ``memory effects'' by this comparison, we find memory effects mainly to be differences in the time-scale of the relaxation process rather than distinct qualitative features. Within the limitations of our isotropic static screening model, we find that, in both approaches, an initial anisotropic and nonmonotonic distribution function relaxes in a three-stage process in which the distribution becomes monotonic before it loses its anisotropy.