Ellipsoidal InAs quantum dots observed by cross-sectional scanning tunneling microscopy

Abstract

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Analysis of the modified optical properties and band structure of GaAs1−xSbx-capped InAs/GaAs quantum dots

“…7. The QDs were found to have an ellipsoidal shape similar to that already reported for InAs/GaAs QDs, 30 with a constant diameter of 25 nm. The QD height (h) was found to progressively increase with the Sb content from 3.3 (0% Sb) to 7.5 nm (14% Sb), and then remains constant, as reported in Ref.…”

Structure of quantum dots as seen by excitonic spectroscopy versus structural characterization: Using theory to close the loop

“…6 The sample was cleaved at the perpendicular ͑110͒ surface enabling STM with atomic resolution to image the cross-sectional surface through the QDs. 11,13 The XSTM results are from one of the QDs presenting the largest cross-section. 11,13 The bias applied to the sample was −2.8 V and under these circumstances, electrons tunnel from the sample to the tip from the occupied valence-band/QD hole states and the total current is mainly sensitive to topographic profiles of the sample surface and to a much smaller extent sensitive to the electronic contrast ͑offset GaAs valence band and QD hole state͒.…”

“…The final shape and composition profile are selected from such a set of guessed inputs by fitting the measured outward relation of the QD on the cleaved surface. 11,13 Thus, a single XSTM measurement often produces a few final SSC models, all consistent with the same measured QD relaxation profile. Second, given that the application of the XSTM procedure to million-atom QDs reveals, in the final analysis, only global structural features, i.e., SSCs, one wonders to what extent is this restricted/specific structural information sufficient to determine other physical properties, such as detailed spectra.…”

“…5,[11][12][13] Unlike crystalline solids, where refinement of x-ray diffraction experiments tends to produce a rather unique, narrowly defined crystal structure whose description is mostly independent of the input guess, 15 XSTM is different in two principal ways. First, deducing the composition profile requires first guess of the shape of the QD-the "usual suspects" are the ones with high symmetry such as truncated pyramids, cones, and ellipsoids.…”

Atomic scale characterization of Mn doped InAs/GaAs quantum dots

“…In the past we have used cross-sectional scanning tunneling microscopy ͑X-STM͒ to image the structural properties of individual QDs. 7 The same technique was used by us to analyze individual Mn impurities in detail 8 and thus X-STM is an ideal tool to study the incorporation of Mn in InAs QDs. Such analysis should be able to resolve several controversies that exist in this young field of the growth of magnetic III/V QDs.…”