Berlin 2008 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 55: GaN: preparation and characterization II
HL 55.4: Vortrag
Freitag, 29. Februar 2008, 11:15–11:30, ER 164
In-situ investigation on the surface electronic structure of GaN(0001)-2×2 — •Richard Gutt, Pierre Lorenz, Marcel Himmerlich, Juergen A. Schaefer, and Stefan Krischok — Institut für Physik and Institut für Mikro- und Nanotechnologien, TU Ilmenau, P.O. Box 100565, 98684 Ilmenau, Germany
The surface electronic structure of GaN(0001)-2×2 surfaces has been studied in-vacuo directly after growth. GaN thin films have been deposited on 6H-SiC(0001) by plasma assisted molecular beam epitaxy. After growth, the samples were cooled down in nitrogen plasma leading to a 2×2 reconstruction measured by reflection high energy electron diffraction. Further characterization by atomic force microscopy as well as ex-situ X-ray diffraction and photoluminescence proves a high sample quality. The presented X-ray photoelectron spectroscopy data show stoichiometric GaN with no evidence of contaminations and a bulk valence band structure in excellent agreement with recently published DFT calculations [1]. Ultraviolet photoelectron spectroscopy detects two additional surface states, 2 eV and 3 eV below EF. The 2×2 reconstruction is a necessary condition for the occurrence of the state at 2 eV. Storage under typical UHV conditions (<2·10−10 mbar) for several hours results in a disappearance of both the reconstruction and the 2 eV state, indicating an extremely high surface reactivity. In addition, a very high reactivity towards oxygen and water is found and will be discussed in another contribution.
D. Segev, C.G. Van de Walle, J. Cryst. Growth 300 (2007) 199