Defect studies on silicon and silicon–germanium for PV and optoelectronic applications

Abstract

Defect monitoring and engineering techniques were applied to multicrystalline silicon grown from electronic grade silicon scraps and strained silicon–germanium alloys to test their suitability for low-cost photovoltaics and high-speed electronics, respectively. The combination of lifetime, photoluminescence and electron beam induced current (EBIC) measurements was found a very effective practice for the analysis of the effect of impurities on the electrical activity of grain boundaries and dislocations in multicrystalline silicon. Room temperature photoluminescence has been also used to monitor the effect of various cell fabrication process steps on the local recombination activity of defects. The application of the EBIC technique was found as well a good tool for a quantitative determination of threading dislocation density in Si–Ge alloys, in view of the optimisation of the low energy plasma-enhanced chemical vapour deposition (LEPECVD) used for their growth.