We have introduced a new method of the study of fast recombination in
a-Si:H, based on the measurement of the extraction time of the charge
carrier reservoir generated by a short intensive light pulse. We demon
strate the advantages of the integral mode of the measurement of these
photo-SCLC transients. We have found a clear transition from monomole
cular to bimolecular recombination at a generation rate of about 10(18
) cm(-3). The deduced coefficient of the bimolecular recombination is
smaller than the same coefficient found from optical pump and probe me
asurements. To explain the experimental results we propose a model bas
ed on the Auger recombination of two free and one trapped charge carri
ers.