Si(111)(7×7) dangling bond contribution to surface recombination

We correlate photoconductivity with surface characterization in order to probe the influence of surface properties of Si(111) on carrier dynamics. Results on the clean (7×7) reconstructed surface indicate that carrier recombination at this surface is fast, with a surface recombination velocity measured to be ≥2×10⁶ cm/s. This is consistent with the notion of midgap dangling bond states acting as effective recombination centers. Combining our results and the present understanding of the (7×7) electronic structure, we estimate the carrier capture cross section for dangling bonds to be ∼10⁻¹⁵ cm². We also investigate the effect of processing and find that carrier dynamics is strongly influenced by trace impurities below the detection limit of conventional surface characterization techniques.