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.

Controlling the Spontaneous Emission Rate of Single Quantum Dots in a Two-Dimensional Photonic Crystal

“…This extended lifetime may find applications in QD-based photonic devices (e.g., switching), including quantum information processing (e.g., quantum memory). It also shows that reported QD lifetime reduction due to surface proximity effects [13] should not limit the performance of PC-QD single photon sources. We find good agreement between these results and FDTD simulations of SE in the photonic crystal.…”

Size dependence of the wavefunction of self-assembled InAs quantum dots from time-resolved optical measurements

“…We exclude that this effect is due to tunneling out of the QDs, which has been observed only within 15 nm from a surface. 18 An increased nonradiative loss may be due to scattering or absorption at the surface of the etched samples. This dissipation at the surface is modeled as a thin absorbing surface layer, which creates an optical surface state.…”

Exciton and multiexciton optical properties of single InAs/GaAs site-controlled quantum dots

“…Wang et al demonstrated an important broadening of the PL lines in InAs/GaAs self-assembled QD when the wetting-layersurface distance is reduced below 40 nm, accompanied by a strong reduction of the emission efficiency and recombination times for distances below 20 nm. 21 Such broadening can be explained by the spectral diffusion effects since random carrier trapping to the QD surrounding defects or impurity vacancies induces electric field fluctuations with time, originating a slow stochastic movement of the peak energy. 22 In our SCQDs the thickness of both GaAs capping and buffer layer are thin, 20 and 15 nm, respectively, and residual defects can be expected arising from the cleaning process and crystal quality (impurities, roughness, point defects, etc.…”