7 February 2006 Self-assembly of heterojunction quantum dots(HeQuaDs)
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Quantum dots (QDs) have been receiving considerable attention due to the unique properties, which arise due to the confinement of the electron and holes in a lower band gap material. The InAs on GaAs material system is one of the most studied combinations in which quantum dots form during epitaxy. These QDs form in a Stranski Krastanov manner via a self-assembly process in which the dots nucleate at a critical adatom coverage on a wetting layer of InAs. QDs may be vertically aligned by using the residual strain above a buried dot layer to enhance the nucleation of the second layer of dots. In this work, we show the formation of QDs, which are composed of multiple materials, can be formed through a marriage of these two concepts. In this particular demonstration, we formed InAs dots on GaAs andcrowned the QDs with GaSb and encapsulated the entire structure with GaAs. Atomic Force Microscopy shows additional nucleation between the InAs layers has been minimized and cross-sectional transmission electron microscopy shows the formation the composite structure. Transmission electron microscopy indicated a clear boundary between the GaSb and InAs regions. AFM analysis of the HeQuaD structure shows that GaSb material grows mainly on the two (1 1 0) inclined facets. Thus, the HeQuaD is elongated along the (1 1 0) direction. We have also obtained preliminary photoluminescence (PL) from a 3 layer GaS/InAs HeQuaD structure with a peak around 1.3 microns.
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K. G. Eyink, K. G. Eyink, D. H. Tomich, D. H. Tomich, L. Grazulis, L. Grazulis, J. J. Pitz, J. J. Pitz, K. Mahalingam, K. Mahalingam, J. Shank, J. Shank, S. Munshi, S. Munshi, B. Ulrich, B. Ulrich, } "Self-assembly of heterojunction quantum dots(HeQuaDs)", Proc. SPIE 6129, Quantum Dots, Particles, and Nanoclusters III, 61290B (7 February 2006); doi: 10.1117/12.647021; https://doi.org/10.1117/12.647021

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