Temperature dependence of a slow component of excess carrier decay curves

In the photoconductivity decay measurement, a slow component is often observed, especially for wide-bandgap materials, e.g., SiC and GaN. This slow component is thought to be due to minority carrier traps: excited minority carriers are captured by the traps, and excess majority carriers remain in the band. From temperature dependence of the slow component, it is in principle possible to estimate trap properties. However, the necessary analysis is not simple because both the capture and emission processes should be taken into account, in contrast to the transient capacitance measurement, where only the emission process needs to be considered. In this paper, excess carrier decay curves are calculated for four typical cases, taking 4H-SiC as an example, and it is discussed how the trap properties can be deduced from the decay curves.