Excitonic luminescence linewidths in AlGaN alloys with high aluminum concentrations

In this work, we report a study of the behavior of linewidths of excitonic photoluminescence transitions measured at 10 K in AlGaN alloys for high Al concentrations of 0.5 and 0.7. Our samples were grown by low-pressure metalorganic chemical vapor deposition on (0001) oriented sapphire substrates. We find that the values of the excitonic linewidths we measure agree very well with those calculated using a model in which the broadening effect is assumed to be due to compositional disorder in completely random semiconductor alloys thus attesting to an excellent quality of our samples even with high Al concentrations. (C) 2002 American Institute of Physics.