Ultranarrow Luminescence Lines from Single Quantum Dots

We report ultranarrow (<0.15meV) cathodoluminescence lines originating from single InAs quantum dots in a GaAs matrix for temperatures up to 50 K, directly proving their δ-function-like density of electronic states. The quantum dots have been prepared by molecular beam epitaxy utilizing a strain-induced self-organizing mechanism. A narrow dot size distribution of width 12±1nm is imaged by plan-view transmission electron microscopy. Cathodoluminescence images directly visualize individual dot positions and recombination from a single dot. A dense dot array (~10¹¹dots/cm²) gives rise to a distinct absorption peak which almost coincides with the luminescence maximum.