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O: Oberflächenphysik
O 17: Zeitaufgelöste Spektroskopie I
O 17.2: Talk
Tuesday, March 25, 2003, 11:30–11:45, FOE/ORG
Dynamics of optically excited electrons at semiconductor surfaces: 2PPE at InP(100) — •Lars Töben, Lars Gundlach, Thomas Hannappel, Ralph Ernstorfer, Rainer Eichberger, and Frank Willig — Hahn-Meitner-Institute, Glienicker Str. 100 Berlin, Germany
Unoccupied electronic surface states and bulk states of a semiconductor can be populated via optical excitation. Since a few years energy- and time-resolved two-photon photoemission (tr-2PPE) with femtosecond resolution has been employed as surface sensitive technique for investigating the carrier dynamics following optical excitation.
Experimental results will be presented for the In-rich (2x4)-reconstructed surface of InP(100) with time-resolution better than 70 fs. The well-known lowest unoccupied surface state C1 was populated with a laser pulse of 1.75 eV photon energy. From the energy distribution measured for increasing time delay the decay of the electron population from the surface state C1 into isoenergetic bulk states was determined. The results reveal the timescale for scattering of electrons between the surface state and bulk levels and that for cooling of the hot electron distribution down to lattice temperature.