Berlin 2008 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 36: Poster III

HL 36.42: Poster

Wednesday, February 27, 2008, 16:30–19:00, Poster D

Oxidation of GaN(0001)-2×2 surfaces by oxygen and water — •Pierre Lorenz, Richard Gutt, Juergen A. Schaefer, and Stefan Krischok — Institut für Physik and Institut für Mikro- und Nanotechnologien, TU Ilmenau, P.O. Box 100565, 98684 Ilmenau, Germany

Experimental and theoretical studies show a high reactivity of GaN surfaces, which is of importance for various applications [1]. We have performed an in-situ analysis of the interaction of oxygen and water with clean and stoichiometric 2×2 reconstructed GaN(0001) surfaces grown on 6H-SiC(0001) by plasma assisted molecular beam epitaxy, with an RMS roughness well below 1 nm measured by atomic force microscopy. For the as-grown samples, two surface states at 2 eV and 3 eV below E_F can be found in the ultraviolet photoelectron valence band spectra. Upon oxygen exposure, drastic changes are observed. Within the first 4 Langmuir of oxygen, the state at 2 eV as well as the 2×2 superstructure vanishes. Additionally, the work function φ increases by 0.3 eV and a downward bend bending of 0.4 eV is observed. For higher exposures, φ remains constant and the valence band spectra merge into curves with two distinct oxygen related states at 6 eV and 11 eV in agreement with earlier works [2,3]. The reaction to water shows a comparable behaviour, with a disappearence of the 2 eV surface state after an exposure of 0.2 L.
C.-L. Hu et al. , Chem. Phys. Lett. 424 (2006) 273 [2] V.M. Bermudez, J.Appl. Phys. 80 (1996) 1190 [3] V.M. Bermudez and J.P. Long, Surf. Sci. 450 (2000) 98