Photoluminescence from a single GaAs/AlGaAs quantum dot

Isolated single quantum dots of different size have been fabricated by laser-induced local interdiffusion of a GaAs/AlGaAs quantum-well structure. Microscopic photoluminescence (PL) reveals a splitting and a blueshift, which depend systematically on dot size. The distinct PL peaks separated in energy by up to 10 meV are attributed to recombination between zero-dimensional (0D) electron and hole states. Complete quantization and inherent exclusion of inhomogeneous broadening in a single dot structure cause PL linewidths below 0.5 meV. The strength of the higher-energy transitions indicates the slowed energy relaxation theoretically predicted for 0D systems.