Excitonic emission dynamics in homoepitaxial AlN films studied using polarized and spatio-time-resolved cathodoluminescence measurements

Excitonic emission dynamics in homoepitaxial AlN films grown on a freestanding substrate prepared by the physical-vapor-transport method were examined. Reflecting the low threading dislocation density ( 10 4cm - 2), room-temperature cathodoluminescence intensity images mapped at the free A-exciton energy exhibited homogeneous contrasts. Low-temperature cathodoluminescence peaks at 6.041₅ and 6.028₇ eV, which were polarized parallel and perpendicular, respectively, to the c-axis, exhibited identical risetimes and short lifetimes; the latter coincided with the temporal delay of neutral donor-bound exciton emissions. These results support the assumption that the two peaks originate from the recombination of free A-excitons of irreducible representations Γ 1 and Γ 5, respectively.