Enhanced room-temperature luminescence efficiency through carrier localization in AlxGa1-xN alloys

Collins, C. J.; Sampath, A. V.; Garrett, G. A.; Sarney, W. L.; Shen, H.; Wraback, M.; Nikiforov, A. Yu.; Cargill, G. S.; Dierolf, V.
January 2005
Applied Physics Letters;1/17/2005, Vol. 86 Issue 3, p031916
Academic Journal
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 (∼375 ps) comparable to that seen in low defect density (∼108 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 (>1010 cm-2) of the films by inhibiting movement of carriers to nonradiative sites.


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