Determining the excess carrier lifetime in crystalline silicon thin-films by photoluminescence measurements

A valuable nondestructive measurement and analysis method for determining individual excess carrier lifetimes in multilayer systems is presented. This is particularly interesting for the characterization of crystalline silicon thin-film samples consisting of an electrically active epitaxial layer on top of a highly doped crystalline substrate. The analysis principle is based on a comparison between a measured photoluminescence intensity ratio and associated simulated radiative recombination ratios for samples with different epitaxial layer thicknesses. It benefits from the fact that for low excess carrier lifetimes within the epitaxial layer the carrier concentration in the said layer is limited by bulk recombination, while for high carrier lifetimes surface and interface recombination is dominating. In order to verify this measurement and analysis principle, results of a set of crystalline silicon thin-film samples with varying epitaxial layer thickness on a highly doped Czochralski substrate are presented