Published in Phys. Stat. Sol. (c) 0, 2938 (2003).

In-situ ellipsometry:Identification of surface terminations during GaN growth

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

Abstract

Spectroscopic ellipsometry (SE) is used to determine GaN surface termination during growth with metal-organic vapor phase epitaxy (MOVPE) by a correlation to well known results of plasma-assisted molecular beam epitaxy (PAMBE). The results manifest that in MOVPE under typical growth conditions the surface is not terminated by a Ga-bilayer as suggested for MBE. Moreover, it turns out that ellipsometry can be used to characterize the surface reconstruction in wurtzite GaN similar as reflectance anisotropy does for cubic III V-compounds. The optical spectra for the PAMBE reveal clear differences between growth under Ga-rich and N-rich conditions,which are attributed to the presenceof a Ga-bilayer and various N-rich reconstructions on the surface.

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