Photoconductance Determination of Carrier Capture Cross Sections of Slow Traps in Silicon through Variable Pulse Filling

The capture cross sections are a key metric to characterize carrier traps in semiconductors. In this article, photoconductance measurements are used to estimate the capture cross sections of traps that are induced by thermal donors in Czochralski-grown silicon wafers. Here, we use a pulse-filling technique with light-emitting diode excitation to measure the capture rate. The measured capture rates are shown to be similar to the values that were measured previously by deep-level transient spectroscopy. Our method allows the contactless measurements of the capture cross sections. The minority carrier cross sections for the two distinct trap states that are studied here are of the order of 10-18 cm2 and the majority carrier cross sections are orders of magnitude smaller. Therefore, it is concluded that the slow traps that are originating from the thermal donors are dominated by the minority carrier trapping.