The optical and structural properties of InGaN epilayers with very high indium content

We present the results of optical and structural investigations of InGaN epilayers grown by Metallorganic Vapour Phase Epitaxy (MOVPE). The peak energies of characteristic photoluminescence (PL) bands allow us to identify regions of crystal with different mean InN: (InN + GaN) fraction in the range from 0.1 to nearly 1 in selected samples. The PL peak energy and the optical absorption band edge are strongly intercorrelated, the Stokes' shift and the Urbach tailing energy both increase with InN fraction. High-resolution energy dispersive X-ray analysis (EDX), coupled with scanning electron microscopy (SEM) and cathodoluminescence (CL) imaging, helps to establish striking microscale correlations between optical and structural properties. Finally, X-ray absorption fine structure (XAFS) at the In and Ga K-edges reveals characteristic local structure on the atomic scale for InGaN solid solutions over the available range of In:Ga composition ratios. (C) 1999 Elsevier Science S.A. All rights reserved.