Quantitative compositional analysis of InAs/GaAs quantum dots by scanning transmission electron microscopy

We present a quantitative technique for the direct compositional analysis o f quantum dots (QDs), in which scanning transmission electron microscopy is applied to a capped InAs/GaAs QD layer in a structure also containing InxG a1-xAs/GaAs quantum well (QW) layers to provide an internal calibration of the In content. By obtaining energy dispersive x-ray analysis line scans th rough both QWs and QDs, the composition of the QDs can be determined by ref erence to the known composition of the QWs. In this article the method is d escribed and demonstrated using two InAs/GaAs structures in which the QDs a re nominally identical, but with different In composition in the calibratio n QW layers. We find that the QDs in both structures have an In composition of 65%-67% and the associated wetting layers contain approximately 12% In. (C) 2001 American Institute of Physics.