Christian Wetzel, E.E. Haller, R. Jeanloz, J Ager III, Lawrence Berkeley National Laboratory and University of California, MS 2-200, Berkeley, CA 94720; R. Held, Department of Chemical Engineering, Minnesota University, Minneapolis, MN 55455; I. Akasaki, H. Amano, Department of Electrical and Electronic Engineering, Meijo University, Nagoya, Japan
Technical Program of the 38th Electronic Materials Conference, June 26-28, Session S: Nondestructive Testing, S6, 3:50PM
Abstract
Epitaxy of high quality GaN still suffers from the lack of a lattice matched substrate material. Incorporation of an intermediate-buffer layer, typically deposited at lower temperatures, has proven to significantly improve crystalline quality and device performance. However, optical characterization of the buffer layer has not been feasible up to now due to its small thickness typically lying below 50A. Here we present a method to positively register the presence of an AlN buffer layer and to assess its structural quality in an easy-to-apply, purely optical approach. From a combination of Raman scattering and infrared spectroscopy in the optical phonon region, we identify the individual layers of the heterostructure. We demonstrate the methods versatility with GaN films deposited on various substrates comprising sapphire and Si.
Work supported by US DOE under Contract DE-AC03-76SF00098. C.W. thanks the Deutsche Forschungsgemeinschaft for a grant.
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