LIFETIME DISTRIBUTION IN A-SI-H - GEMINATE-PROCESS, NONGEMINATE-PROCESS AND AUGER-PROCESS

The lifetime of excess carriers in a-Si:H at T less-than-or-equal-to 30 K is investigated by frequency resolved spectroscopy as a function of excitation intensity and temperature to obtain detailed information on the recombination processes. In this temperature range two independent recombination channels are observed with lifetimes of about tau(1) = 3 ms and tau(2) = 3-mu-s, respectively. At low excitation intensities I(exc) both exhibit constant lifetime independent of I(exc) following the predictions of the geminate pair model. In the high excitation region the lifetime shortens with increasing I(exc), which is the typical behavior of a nongeminate recombination process. The behavior of both the luminescence intensity I(PL) and the lifetime taupoints to Auger recombination as the dominating nongeminate process in the temperature range T < 10 K and to a super-position of Auger and distant-pair recombination at higher temperatures.