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HL: Fachverband Halbleiterphysik

HL 49: Quantum dots: preparation and characterization

HL 49.4: Talk

Friday, March 27, 2009, 11:00–11:15, BEY 81

Electric field control of vertically tunnel coupled InP quantum dots — •Elisabeth Koroknay, Wolfgang-Michael Schulz, Robert Roßbach, Michael Jetter, and Peter Michler — Institut für Halbleiteroptik und Funktionelle Grenzflächen, Stuttgart, Deutschland

Controllable interactions between coupled quantum dots (QD) are of great interest with regard to quantum information technology. Based on previous research on self organized QD single layers on (Al,Ga)InP barriers the self organized vertical alignment is investigated. The QDs grown by metalorganic vapour phase epitaxy are separated by a spacer layer of the corresponding barrier material. The first QD layer induces a strain field which has influences on the QD growth of the second layer. This influence was investigated by transmission elecron microscopy, atomic force microscopy and photoluminescence measurements. By controlling properly the amount of deposited material, asymmetric QD molecules can be grown, where the high energetic smaller sized QD is located above the low energetic larger sized QD. The electronic coupling between these QDs is achieved by a tunneling process of charge carriers. The influence of the barrier thickness on the tunneling probability can already be seen in ensemble PL measurements. In order to realize controllable interactions between the quantum dot layers, the tunnel coupling is varied by an electric field along the molecule axis. A n-i-schottky structure with the QD molecules in the intrinsic region is used to tilt the overall potential by applying an electric field. In this way the energy levels of the QDs can be tuned in and out of resonance.