RUE-induced carrier lifetime degradation

Reactive Ion Etching (RIE) is used in the fabrication of some types of solar cells to achieve a highly directional etch. However, cells fabricated using RIE have lower than expected efficiency, possibly caused by increased carrier recombination. Characterisation of the carrier lifetime in solar cells was conducted using the quasi steady state photoconductance (QSSPC) measurement technique. Substantial effective lifetime degradation was observed for silicon samples processed by RIE. Lifetime degradation for samples where RIE etches into silicon is found to be permanent, while for samples where RIE etches only on dielectric layers of SiO2 grown on the wafer, the lifetime degradation is found to be reversible. The reversible degradation in RIE-processed samples is associated with radiation damage. By reducing the proportion of a wafer exposed to RIE, the degradation of the effective lifetime of RIE-etched silicon samples can be minimised, and the performance of silicon solar cells can be improved significantly. Copyright (C) 2010 John Wiley & Sons, Ltd.