Regensburg 2000 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 27: Poster II: SiC (1-7), Ultrakurzzeitdynamik (8-15), Halbleiterlaser (16-20), GaN (21-38), III-V Halbleiter (39-56), Photovoltaik (57-64), Störstellen (65-68), Tern
äre Halbleiter (69-70)
HL 27.44: Poster
Mittwoch, 29. März 2000, 14:00–19:00, A
Organic modification of GaAs Schottky contacts — •S. Park1, T. U. Kampen1, W. Braun2, and D. R. T. Zahn1 — 1Institut für Physik, Technische Universität Chemnitz, D-09107 Chemnitz, Germany — 2BESSY GmbH, D-12489 Berlin-Adlershof, Germany
Recently, an interlayer of a prototype organic molecule, 3,4,9,10-perylene tetracarboxylic dianhydride (PTCDA), was inserted between the metal and the semiconductor substrate. The device shows rectifying behaviour, remarkable I-V characteristics and high cutoff frequencies in favor of microwave applications. In order to understand the interface formation, the effect of a thin PTCDA interlayer on a Schottky contact of Mg/Se-GaAs(100)-(21) was investigated by high resolution photoemission spectroscopy using synchrotron radiation. The adsorption of PTCDA molecules (∼0.3 ML) on Se passivated GaAs(100) surface preferentially occurs at defect sites, resulting in a reduced surface band bending. Upon subsequent Mg deposition up to 15ML, the formation of ternary MgGaSe is observed. Probably, the deposited PTCDA molecules react with Mg, as judged by the valence band spectra. The position of the Fermi level above the valence band maximum amounts to 0.65 eV upon 2.3 ML Mg deposition, corresponding to the Fermi level in a sample without PTCDA interlayer. However, the typical adsorbate-induced surface states at low Mg coverage of n-type GaAs do not appear in the presence of PTCDA molecules. This reveals the importance of an organic interlayer for intentional modifications of the metal-GaAs interface.