Investigation of coupling in naturally occurring GaAs quantum dots

We report on the photoluminescence (PL) imaging of GaAs quantum dots (QDs) formed by islands of quantized thicknesses in a 2 nm thick Al0.3Ga0.7As/GaAs/Al0.3Ga0.7As quantum well (QW) by means of near-field scanning optical microscopy. Discrete spectra associated with the QDs are observed and studied. Individual QDs are imaged with a resolution of 150 nm. Energy degeneracy which is sometimes observed between nearby QDs suggests the possibility of quantum mechanically coupled dots. Constraints on the observation of coupling are discussed.