Partners and International Organizations
(English)
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BE, BG, CH, CZ, DE, DK, ES, FI, FR, HU, IE, IL, IT, LT, MT, NL, PL, SE, TR, UK
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Abstract
(English)
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We developed and studied ordered arays of semiconductor quantum dots (QDs) suitable for use as optical gain material in novel semiconductor lasers. The site-controlled (In)GaAs/(Al)GaAs QDs were fabricated by organometallic vapor phase epitaxy (OMVPE) on (111)B GaAs substrates patterned with arrays of inverted tetrahedral pyramids defined by {111}A crystal facets. Two types of QD structures were investigated: (i) dense, sub-µm pitch arrays of QDs; and (ii) 'isolated' QDs. The former type is suitable for incorporation into multi-QD laser cavities, whereas the latter is useful for investigation of single- or few-QD lasers. The QD structures were characterized using atomic force microscopy (AFM), low-temperature photoluminescnce (PL) and cathodoluminescence spectroscopy, and their electronic states and optical transitions were modelled theoretically. The major results of this research efforts are: 1. We demonstrated, for the first time, the realization of ordered QD arrays with pitch as small as 100nm (density of ~10^10cm^-2) with PL inhomgeneous broadening of less than 6meV; 2. We implemented direct injection of charge carriers into single QDs via connected QWRs, yielding electrically pumped single photon sources; 3. We integrated a single, site controlled QD into a high-finesse photonic crystal nanocavity, and observed the weak coupling of the dot emission into the cavity mode. These results represent significant progress towards the demonstration of QD lasers based on or-dered arrays of QDs, for which enhanced performance as compared to conventional diode lasers is expected. In particular, they confirm the potential of ordered QDs made by OMVPE on patterned substrates as useful QD systems for laser and other optoelectronic device applications.
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