Defect density dependence of luminescence efficiency and lifetimes in AlGaN active regions exhibiting enhanced emission from nanoscale compositional inhomogeneities

AlGaN epilayers grown by plasma-assisted molecular beam epitaxy and exhibiting high internal quantum efficiency (up to 30%) are incorporated into double-heterostructure devices grown on base layers of varying defect density. Growth of these AlGaN active layers, having increased emission from localization of carriers in regions of nanoscale compositional inhomogeneities, is found to benefit from base layers of reduced defect density, including thick AlGaN templates grown by hydride vapor phase epitaxy. Nonlinear radiative processes are observed at high optical excitation for layers grown on lower defect base layers. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.