Enhanced room-temperature luminescence efficiency through carrier localization in AlxGa1-xN alloys -: art. no. 031916

AlGaN samples grown by plasma-assisted molecular-beam epitaxy on sapphire (0001) substrates, with 20 %-50 % Al content and without the use of indium, show intense room-temperature photoluminescence that is significantly redshifted, 200-400 meV, from band edge. This intense emission is characterized by a long room-temperature lifetime (similar to375 ps) comparable to that seen in low defect density (similar to10(8) cm(-2)) GaN. Room-temperature monochromatic cathodoluminescence images at the redshifted peak reveal spatially nonuniform emission similar to that observed in In(Al)GaN alloys and attributed to compositional inhomogeneity. These observations suggest that spatial localization enhances the luminescence efficiency despite the high defect density (> 10(10) cm(-2)) of the films by inhibiting movement of carriers to nonradiative sites. (C) 2005 American Institute of Physics.