Correlation Between Structure And Photoluminescence Properties In Ingan Epilayers With Thicknesses Below And Above Critical Thickness

The layer strain and its relaxation effects on the photoluminescence (PL) of InGaN layers are studied using confocal microscopy. The relaxation imposed structural changes are studied by X-ray diffraction (XRD) reciprocal space mapping and atomic force microscopy. Initial layer relaxation generated misfit dislocations were observed by confocal microscopy as intersecting parallel lines of lower PL intensity. The splitting of the PL spectrum into several PL bands indicated an onset of changes in the layer structure, which were confirmed by XRD measurements. The PL bands were attributed to two sub-layers of the sample: A relaxed upper sub-layer and a strained sub-layer underneath. Bright spots, approximately 250 nm in diameter, were observed on the background of the inhomogeneous PL intensity distribution due to fluctuations of In content. The bright spots correspond to column-like structures with relaxed lattice, In content as in the initial strained layer, and lower density of nonradiative recombination centers than that in the surrounding background. (C) 2013 AIP Publishing LLC.