Abstract
Within the context of the multiple-trapping model, we discuss different theoretical ways of defining a transit time in the time-of-flight experiment. A new definition based on the first moment with respect to space of the free-carrier distribution is proposed. At the same time various experimentally used definitions of transit time are identified and the corresponding operational values are extracted from Monte Carlo simulated time-of-flight current traces for different field strengths and temperatures, with either an exponential or a linear density of tail states. A comparison between the theoretical and Monte Carlo results for the different approaches is made. Our calculations show that definitions of transit time that emphasize the fastest of the drifting carriers exhibit a larger electric field dependence and a smaller apparent activation energy than definitions which are based on the totality of excess charge carriers. Consequently we conclude that, if one analyses drift-mobility data in the multiple-trapping framework, one has to use a theoretical definition which is compatible with the procedure used in extracting the experimental transit times.