TRANSPORT ANALYSIS OF THE THERMALIZATION AND ENERGY RELAXATION OF PHOTOEXCITED HOT-ELECTRONS IN GE-DOPED GAAS

A very fast broadening, thermalization, and cooling of an initially na rrow photoexcited electron distribution was recently observed in the t ime- and frequency-resolved electron-acceptor luminescence of p-type b ulk GaAs:Ge for near-band-gap excitation at low excitation densities a nd temperatures. As the short thermalization times could not be explai ned by the standard rates for the conventional carrier-carrier, carrie r-impurity, and carrier-phonon scatterings, unconventional types of th ermalizing carrier interactions were originally suggested to interpret the data. In contrast, the present analysis restricts itself to the c onventional scattering mechanisms, but attempts to explain the fast th ermalization and cooling rates by accounting for the finite experiment al pulse-repetition rates and the resulting presence of neutral donors of the amphoteric germanium, causing a very effective additional elec tronic energy-relaxation channel via impact ionizations of Ge donors.