Published online by Cambridge University Press: 28 February 2011
Radiative and non-radiative recombination in porous silicon (PSi) is measured under a wide injection range by detecting of photoluminescence (PL) and free-carrier absorption (FCA) decay. We used 2.34 eV and 140 ns light pulses for carrier excitation in PSi flakes. The excited carriers were probed by focused cw IR light and the carrier concentration was calculated by using the free-carrier absorption cross section of bulk (c-Si). The results demonstrate a scaling between the total PL yield in the S-band, integrated over wavelengths, and the free carrier concentration. At lower injections the observed free carrier and PL decay follow a similar, density-independent stretched-exponential law. At injections approaching 1018 cm−3, a fast recombination component appears reducing the lifetime by a factor of ten. This component is attributed to Auger recombination of separated e-h pairs on a set of Si subclusters.