Optical properties of single InAs quantum dots in close proximity to surfaces

Abstract

The optical properties of single InAs∕GaAs quantum dots (QDs) were studied as a function of their distance from the air∕GaAs interface. A short-period superlattice structure allows us to controllably shorten the distance between the QDs and the surface in 6-nm steps. The QD luminescence intensity and lifetime measurements show that quantum tunneling effect results in a sharp reduction in fluorescence efficiency and lifetime when the wetting-layer–surface distance is within 9 nm. For distances between 15 and 40 nm, broadening of the photoluminescence linewidths of single QDs was observed. Since exciton recombination time and efficiency are in this case unchanged with respect to bulk QDs, the observed line broadening is most likely due to dephasing or spectral diffusion processes.