denecke-mrssp-468-263

Data for reference denecke-mrssp-468-263

X-ray Photoelectron Diffraction Measurements of Hexagonal GaN(0001) Thin Films

R. Denecke, J. Morais, C. Wetzel, J. Liesegang, E.E. Haller, C.S. Fadley

Materials Research Society Symposium Proceedings 468, 263 (1997).

Below is the abstract submitted to the meeting, not the abstract of the published paper:
We report on results of the first x-ray photoelectron diffraction (XPD) measurements obtained for hexagonal GaN thin films. Photoelectron diffraction patterns for Ga 3p and N 1s core level photoemission excited with Al K_α radiation have been collected over the 2π solid angle. The samples under study have been grown by metal organic chemical vapor deposition (MOCVD) on sapphire substrates at the Technical University of Munich, Germany [1]. The measurements were performed both on the untreated surface and after heating the sample in UHV to higher temperatures to remove surface contaminants. We observed clear hexagonal patterns for both Ga 3p and N 1s core level photoemission which indicate a high degree of near-surface crystalline order. We have also made a comparison of our data with simulated XPD patterns from multiple-scattering cluster calculations. From the untreated samples we derive that the surface contamination by O and C is very small, still allowing precise XPD measurements. Additionally, C and O are mainly found on the surface and not in the boundaries of the hexagonal columns which are characteristic for these thin films and which can be observed under a light microscope. In order to further reveal the near-surface structure, preliminary photoelectron diffraction measurements have also been performed using synchrotron radiation from the Advanced Light Source (ALS). From the high resolution core level spectra one obtains a more detailed view of the surface structure. Work supported by ONR (Contracts N00014-90-5-1457 and N00014-94-1 0162) and DOE, BES, Mat. Sci. Div. (Contract DE-AC03-76SF00098,) and CNPq (Brazil). [l] T. Metzger, H. Angerer, O. Ambacher, M Stutzmann, E. Born, Phys Stat. Sol. (b) 193, 391 (1996).

This paper is part of Gallium Nitride and Related Materials II

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