Surface effects on carrier dynamics: photoconductivity studies on Si (111)

We correlate photoconductivity with surface characterization in order to probe the influence of different surface properties of Si (111) on electron-hole dynamics. Photoconductivity data show that the carrier recombination is influenced strongly by surface structure and chemistry as well as by trace imperfections which are undetectable by conventional surface characterization techniques. Results on the Si(111):As (1×1) surface indicate carrier recombination at this surface is negligible, in contrast to the (7×7) reconstructed surface, where surface recombination is fast, with a surface recombination velocity measured to be ≥2×106 cm/s. We also investigate the effect of sputter induced disorder and compare our finding with results from other techniques. 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.