AlGaN samples grown by plasma-assisted molecular-beam epitaxy on sapphire ͑0001͒ 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 ͑ϳ375 ps͒ comparable to that seen in low defect density ͑ϳ10 8 cm −2 ͒ GaN. Room-temperature monochromatic cathodoluminescence images at the redshifted peak reveal

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... atially nonuniform emission similar to that observed in In͑Al͒GaN alloys and attributed to compositional inhomogeneity. These observations suggest that spatial localization enhances the luminescence efficiency despite the high defect density ͑Ͼ10 10 cm −2 ͒ of the films by inhibiting movement of carriers to nonradiative sites.