Linewidths of excitonic luminescence transitions in AlGaN alloys

In this work, we present a study of the behavior of linewidths of excitonic photoluminescence transitions measured at 10 K in AlGaN alloys as a functi on of Al concentration. Samples we have investigated are grown by low-press ure metalorganic chemical vapor deposition on (0001) oriented sapphire subs trates with low-temperature GaN buffer layers. The Al composition ranged fr om 0%-35%. We find that the values of the excitonic linewidth increase as a function of Al concentration and agree very well with those calculated usi ng a model in which the broadening effect is assumed to be due to compositi onal disorder in semiconductor alloys. The values of the excitonic linewidt hs measured in our samples are considerably smaller than those reported rec ently, thus attesting to the high quality of our samples. (C) 2001 American Institute of Physics.