Trapping and junction-related perturbations of the effective excess carrier lifetime

Quasi-steady-state measurements of the photoconductance versus the illumination intensity are used to determine the effective excess carrier lifetime /spl tau//sub eff/(/spl Delta/n) of Si wafers. Generally, /spl tau//sub eff/(/spl Delta/n) is determined by bulk recombination, surface recombination and diffusion. However, carrier trapping is well known to cause an overestimation of /spl tau//sub eff/. In this work, an additional effect - depletion region modulation (DRM) - is shown to cause a similar overestimation in Si wafers featuring a p-n junction. Additionally, shunting is shown to cause an underestimation of /spl tau//sub eff/. The impact of these distinct effects on /spl tau//sub eff/(/spl delta/n) is demonstrated using analytical equations and PC1D. Furthermore, experimental evidence of DRM is given, using quasi-steady-state lifetime measurements on various Si wafer samples.