Ultrafast carrier dynamics near the Si(100)2×1 surface

We present a time-resolved photoemission study of carrier dynamics near the Si(100)2×{}1 surface. It is found that the dominant contribution to the photoemission process originates from defect states on the Si(100)2×{}1 surface. Enhanced optical absorption is observed for these defect states and carrier exchange between these states and the bulk is observed. The electron density near the surface and the shape of the electron energy distribution are found to change on a very fast time scale. A simple theoretical model is established to extract transport parameters from the observed electron energy distribution.