A general two dimensional study of the power reflection in microwave detected photoconductance technique for lifetime measurement

A rigorous two dimensional analytical study of the microwave detected photoconductance decay system used for non destructive carrier lifetime measurement in silicon wafers is presented. A theoretical two dimensional model is elaborated for the calculation of the excess power reflection caused by a local excess photoconductance with arbitrary lateral distribution. Closed form expressions for a gaussian perturbation are derived without imposing any restriction on the lateral width. The results show that the excess power reflection is a function of the lateral profile of the perturbation. Furthermore, the effect of transient lateral diffusion resulting from pulsed light source extracted value of the lifetime is investigated. It is found that the transient lateral carrier diffusion affects the excess reflectance but should have a minor impact on the extracted value of the carrier lifetime in moderate quality silicon material used in solar cell industry.