Nanoscale compositional fluctuations in single InGaAs/GaAs quantum dots

We report the first investigation of compositional disorder in quantum dots with subnanometer precision. We have investigated the compositional profile of a single InGaAs/GaAs quantum dot. of nominal In content x = 0.5. by using energy-dispersive X-ray spectroscopy (EDX). transmission electron microscopy (TEM). and atomic force and scanning tunneling microscope (AFM-STM) topography. The compositional analysis at nanoscale reveals a number of unexpected features: (i) In enrichment of the centre of the dot (about 65% In content): (ii) In diffusion outside the dot contour: (iii) In depletion of the wetting layer in the surrounding of the dot.