Generalizations of multiple trapping

The multiple trapping model may be applicable to a wide variety of time-dependent processes in semiconductors. However, previous simple treatments developed to explain power-law current transients assumed trapping in an exponential density of states with a constant trapping ‘cross-section'. We present a more detailed analysis of multiple trapping by examining the trapping and emission rates from traps, as well as their occupation. This shift of emphasis, while retaining and enhancing a simple physical picture of the process, allows us to treat several new situations. We give simple results for the effect of repetitive pulses. The effect of variations in trapping ‘cross-section’ among traps is also found to be fairly simple. We classify all possible current transients into five basic types, for which different sets of states dominate the dynamical behaviour, and derive the form of the current transient for each type.