Published in J. Appl. Phys. 94, 6997 (2003).

Surface termination during GaN growth by metal-organic vapor phase epitaxy determined by ellipsometry

C. Cobet (a), T. Schmidtling (a), M. Drago (a), N. Wollschläger (a), N. Esser (a), W. Richter (a), R. M. Feenstra (b), and T. U. Kampen (c)
(a) Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstr. 36, D-10623 Berlin, Germany
(b) Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213
(c) Institut fuer Physik, Technische Universitaet Chemnitz, D-09107 Chemnitz, Germany


Spectroscopic ellipsometry (SE) is used in study GaN films during growth by metal-organic vapor phase epitaxy (MOVPE) and correlation to well known results of plasma-assisted molecular beam epitaxy (PAMBE). Results for the PAMBE reveal clear differences between growth under Ga-rich and N-rich conditions, which are attributed to the presence of a Ga-bilayer on the surface (also seen with low energy electron-diffraction) in the former case. Results for MOVPE surfaces during growth or for surfaces which are stabilized under NH3 are very similar to the N-rich PAMBE result. It is concluded that under normal growth conditions in MOVPE the surface is not terminated by a Ga-bilayer.

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