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.

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