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

We present the results of optical and structural investigations of InGaN ep ilayers grown by Metallorganic Vapour Phase Epitaxy (MOVPE). The peak energ ies of characteristic photoluminescence (PL) bands allow us to identify reg ions 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 optica l 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 micr oscopy (SEM) and cathodoluminescence (CL) imaging, helps to establish strik ing microscale correlations between optical and structural properties. Fina lly, X-ray absorption fine structure (XAFS) at the In and Ga K-edges reveal s characteristic local structure on the atomic scale for InGaN solid soluti ons over the available range of In:Ga composition ratios. (C) 1999 Elsevier Science S.A. All rights reserved.