Gettering is already an integral part of fabricating integrated circuits using Si substrates. It is anticipated that this will also be true for solar cell fabrication in the near future. A readily available technique compatible with solar cell processing is gettering by the Si wafer back surface Al. Recently, available solar cell efficiency studies have shown the beneficial effects of the wafer backside Al, including that of gettering, a wafer backside field, and grain boundary and dislocation passivation. In this article, we report on experimental results which showed that Czochralski Si wafer bulk minority carrier diffusion lengths can be substantially improved by wafer backside Al treatment, which also provided an effect of protection from environmental contamination. In these experiments, only the effect of gettering is present and therefore the results constitute an unambiguous demonstration of the benefits of gettering by Al. © 1995 American Institute of Physics.