The relationship between microstructure and luminescence efficiency, in hetero-epitaxial metalorganic chemical-vapor deposited films grown on c-axis sapphire substrates, was studied. The correlation between threading dislocations (as observed by transmission electron microscopy), surface morphology (as observed by atomic force microscopy), and wavelength-resolved cathodoluminescence imaging was determined directly. It was shown that an inhomogeneity in the luminescence intensity of the films near to the band edge could be accounted for in terms of a simple model in which non-radiative recombination at threading dislocations caused a deficiency of minority carriers and resulted in dark regions in the epilayer.

S.J.Rosner, E.C.Carr, M.J.Ludowise, G.Girolami, H.I.Erikson: Applied Physics Letters, 1997, 70[4], 420-2