Lifetime measurements of stain etched and passivated porous silicon

In this work we present the first experimental study of photocarrier lifetimes in p-type and n-type Si substrates in which stain etched porous silicon (PS) has been formed on the surface. The lifetime values have been obtained before and after the surface passivation of the samples. The surface pasivation has been produced by two different techniques: (i) hydrogen passivation by immersion of the samples in a HF solution; and (ii) deposition of SiNx in a plasma enhanced chemical vapour deposition system. The results show a degradation of the photocarrier lifetime when the porous layers are not adequately passivated. This lifetime degradation is mainly associated to a large concentration of rapid recombination centres located at the Si/PS interface. We have also detected a weak influence of the PS outermost dangling bonds to the photocarrier lifetimes.