InGaN: Direct correlation of nanoscopic morphology features with optical and structural properties

A comprehensive study on the impact of growth modes on the structural and optical properties of thick InGaN layers suitable for photovoltaic application is presented. Samples grown by metalorganic vapour phase epitaxy with different growth rates and thicknesses have been analyzed. The application of slow growth rates result in smooth layers while higher growth rates induce a meandering surface morphology. Using low-temperature cathodoluminescence, a direct correlation of the morphology to local luminescent properties is obtained: the top of meandering structures reveals a spectrally red-shifted emission compared to the emission wavelength expected from the average indium content determined by X-ray diffraction. The origin of this shift is identified and explained by increased indium incorporation on top of the meander due to a spatially localized compositional pulling effect.