Near‐field control of the light emission properties of a symmetric semiconductor quantum dot

Abstract

We study the carrier capture and distribution among the available energy levels of a symmetric semiconductor quantum dot under continuous‐wave optical excitation resonant with the barrier energy levels. We find that at low temperature all the dot level‐occupations but one decrease monotonically with energy. The uncovered exception, corresponding to the second (dark) energy level, displays a steady‐state carrier density exceeding that of the lowest level more than a factor two. The root cause is not radiative recombination before relaxation to lower energy levels, but at the opposite, carrier trapping due to the symmetry‐induced suppression of radiative recombination. We show that spatially resolved photoluminescence spectroscopy can detect the evanescent waves generated by dark states occupations, allowing the observation of such effects. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)