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HL: Fachverband Halbleiterphysik

HL 32: Quantum dots and wires: preparation and characterization I

HL 32.12: Talk

Wednesday, February 27, 2008, 17:15–17:30, ER 270

Self-assembled quantum dots grown by Molecular Beam Epitaxy on InP-substrate for single photon application at 1.55 µm — •Daniela Baierl, Roland Enzmann, Christian Jendrysik, Christian Seidel, Susanne Dachs, Gerhard Böhm, Ralf Meyer, Jonathan Finley, and Markus-Christian Amann — Walter Schottky Institut

Quantum key distribution requires practical sources of single photons with the standard telecommunication wavelength 1.55 µm, thus they can be efficiently transmitted through fiber optics. Self-assembled InAs-quantum dots allow the observation of single photons as long as their surface density is small enough (approximately 1 dot/µm²). To achieve emission at 1.55 µm it is necessary to use InP(001) as substrate material instead of GaAs - dots on GaAs can not provide higher wavelength than 1.3 µm. But instead of dot formation the deposition of InAs on InP or lattice-matched AlInAs and GaInAs matrix-materials leads to elongated structures, so called "’quantum dashes"’. The mechanism which drives this asymmetric growth is not fully understand, but Indium on the surface, where dot-formation starts, plays an important role. By avoiding Indium in the uppermost layers we show the formation of quantum dots, even with low density. We present several realizations of In-free materials, e. g. a thin sublayer GaSb which suppresses In-segregation from the subjacent Indium-containing matrix-material. We also discuss the photoluminescence characteristics which are different to dots on GaAs, because combining Antimony-containing materials with InAs often results in a type-II band-alignment.