Exciton-phonon interactions, exciton binding energy, and their importance in the realization of room-temperature semiconductor lasers based on GaN

Temperature dependence of the linewidths of free-exciton A and B transition s was investigated. Experimental linewidths were fitted to a theoretical mo del considering various interactions of excitons with phonons in addition t o inhomogeneous broadening. It was shown that acoustic phonon scattering mu st also be considered to explain the emission linewidth broadening, in cont rast to a recent report on luminescence linewidths in GaN. These exciton-ac oustic-phonon interactions also explain the fast energy relaxation of free excitons to the bottom of the exciton band, which leads to generally observ ed short free-exciton lifetimes in GaN. The exciton-longitudinal-optic al ( LO)-phonon coupling constant was found to be extremely large. This was expl ained as being due to the Frohlich interaction and the polar nature of GaN. The binding energy of both A and B excitons was found to be 26 meV. The re levance of exciton-phonon interactions and the binding energy of free excit ons in achieving room-temperature exciton-based semiconductor lasers was di scussed. Though exciton-LO-phonon interaction was very strong in GaN, it wa s still possible to observe room-temperature excitons since the exciton bin ding energy is very large. [S0163-1829(98)02648-4].