Hot carrier relaxation and recombination in amorphous semiconductors
The authors report the results of femtosecond optical measurements following injection of a very large density (>1019 cm-3) of carriers with 100 fs 2 eV pulses in a-Si:H. They measure the momentum scattering time of the free carriers ( or approximately=1 eV ps-1), the non-radiative carrier recombination lifetime (1-10 ps), and the decay time of optic phonons into acoustic phonons (<or approximately=100 fgs). The lack of momentum conservation in amorphous materials is responsible for the much shorter characteristic times in a-Si:H than in a typical direct-gap semiconductor such as GaAs.