A study was made of the growth and structural characteristics of green and yellow (529 to 576nm) GaInN/GaN light emitting diodes grown onto two types of c-plane substrate: bulk GaN and sapphire. In this longer wavelength range, depending upon the substrate, were found different strain relaxation mechanisms within the GaInN/GaN quantum well region. In optimized epitaxy, structures on sapphire that contained a low density of threading dislocations within the n-GaN showed virtually no generation of additional misfit dislocations (<108/cm2) or V-defects within the quantum well region for emission wavelengths up to 571nm. On bulk GaN substrate, however, where much fewer threading dislocations reach the quantum wells, strain relaxation was observed by inclined dislocation pairs in green emitters and a high density of edge-type misfit dislocations in yellow emitters. The electroluminescence line width, as well as the efficiency droop, was found to increase with dislocation density in the quantum wells.

Various Misfit Dislocations in Green and Yellow GaInN/GaN Light Emitting Diodes. M.Zhu, S.You, T.Detchprohm, T.Paskova, E.A.Preble, C.Wetzel: Physica Status Solidi A, 2010, 207[6], 1305–8