We present a quantitative technique for the direct compositional analysis of quantum dots (QDs), in which scanning transmission electron microscopy is applied to a capped InAs/GaAs QD layer in a structure also containing InxGa1−xAs/GaAs quantum well (QW) layers to provide an internal calibration of the In content. By obtaining energy dispersive x-ray analysis line scans through both QWs and QDs, the composition of the QDs can be determined by reference to the known composition of the QWs. In this article the method is described and demonstrated using two InAs/GaAs structures in which the QDs are nominally identical, but with different In composition in the calibration 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.
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Zhi et al. (2001) studied this question.
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