Berlin 2008 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 54: Si/Ge

HL 54.13: Vortrag

Freitag, 29. Februar 2008, 13:45–14:00, EW 202

Dopant-induced states in two-dimensional semiconductors — •Philipp Ebert, Sebastian Landrock, and Knut Urban — Institut für Festkörperfoschung, Forschunsgzentrum Jülich, 52425 Jülich

Intentionally inserted impurities, referred to as dopant atoms, are the lifeline of semiconductor devices. They provide free charge carriers into the bands of the host crystal and thereby allow to tune almost all properties of semiconducting materials. These free carriers are generated by the introduction of localized states into the band gap. For suitable dopant atoms these states are close enough to the band edges, that either electrons from the valence band can thermally populate these states (acceptor type states) or electrons in these states can be thermally excited into the conduction band (donor type states). In order to address the origin of these states, we used scanning tunneling microscopy and spectroscopy to probe the local density of states above dopant atoms in a two-dimensional semiconducting √3 × √3 Ga overlayer on Si(111) substrates. We observe two dopant-induced states and additional changes in the density of states. Using a momentum dependent analysis we demonstrate that the presence of dopant atoms shifts parts of the local density of states. These results are discussed using existing models.