Partners and International Organizations
(English)
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A, B, BG, CZ, DK, FIN, F, D, GR, H, IRL, I, LT, N, PL, P, RO, SK, SI, E, S, CH, TR, GB
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Abstract
(English)
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Self-ordering of semiconductor alloys is a useful technique for the realization of novel electronic and optical materials exhibiting new properties due to quantum confinement effects. We have investigated the structure and self-ordering mechanisms of Ga(In)As/(Al)GaAs quantum well (QW), quantum wire (QWR) and quantum dot (QD) nanostructures that are formed during organometallic chemical vapor deposition on nonplanar substrates using different atomic force and electron microscopy techniques. Tapered, AlGaAs vertical QWs grown on V-grooved substrates were formed by changing either the Al content or the substrate temperature during growth. The resulting tapered bandgap QWs should be useful for enhancing carrier capture into connected QWRs. Self-ordered InGaAs/(Al)GaAs QWRs grown on V-grooved substrates show a significant segregation of In at the center of the wires due to enhanced capillarity effects. The segregation was studied quantitatively by analyzing the contrast of transmission electron microscope (TEM) images of the wires. This segregation is useful for enhancing the quantum confinement and controlling the emission wavelength from such QWRs. TEM images of GaAs/AlGaAs QDs grown in inverted pyramids etched onto (111)B GaAs substrate allowed to study the self-limiting growth and structure of such QDs. Thes dots are connected to self-ordered AlGaAs vertical QWRs that can be used to preferentially inject charge carriers into the dots from bulk electrical contacts. Such preferential carrier injection was also studied using theoretical modeling and electroluminescnce experiments. Model of the electronic states in the dots revealed effective coupling between specific QD and vertical QWR states. Light emitting diodes incorporating pyramidal QDs were constructed and their electroluminescence spectra supported the possibility of such preferential injection.
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