Time-Resolved photoluminescence studies of cubic and hexagonal GaN quantum dots

We report time-integrated and time-resolved photoluminescence (PL) experiments on cubic and hexagonal GaN/AlN quantum wells (QWs) and self-assembled quantum dots (QDs). The comparison between nitride nanostructures of different phase allows us to distinguish pure dimensionality effects from the influence of the large polarization-induced electric fields present in the hexagonal nanostructures. The QDs show a weak temperature dependence of the PL intensity and decay time as a result of enhanced exciton localization. Furthermore, the hexagonal nanostructures exhibit longer decay times than the cubic ones due to electric field-induced carrier separation.