Non-radiative distant pair recombination in amorphous silicon

A brief review of the quadrature frequency-resolved spectroscopy (QFRS) data shows that the radiative tunnelling (RT) model, commonly used to interpret the recombination kinetics in amorphous silicon, must be rejected. The dependence of the QFRS spectra on the excitation rate reveals that the shortening of the carrier lifetimes, which is observed for high excitation rates, is not a matter of decreasing electron-hole separations. Instead, it is induced by a directly competing non-radiative recombination channel. In this paper, the distant pair transition is identified as the origin of this channel, ruling out the possibility that it may be related to Auger recombination, as was previously suggested. This is done by calculating the QFRS signal as a function of the excitation rate, subsequently comparing the results with the respective experimental data. It is argued that the data are clearly in favour of an excitonic recombination model. (C) 1998 Elsevier Science B.V. All rights reserved.