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 Karl Franzens University Graz

Graz University of Technology 

Tuning the optical emission of single quantum dots with strain and electric fields
Armando Rastelli
Institute of Semiconductor and Solid State Physics, Johannes Kepler University Linz
17:15 - 18:15 Tuesday 03 December 2013 TUG P2

Optically active quantum dots (QDs) can be made as nanoinclusions of a low-energy-bandgap semiconductor in a matrix with larger energy bandgap. Many recent experiments have demonstrated that these QDs are excellent quantum emitters, which can be used as sources of triggered single photons, indistinguishable photons and polarization entangled photon pairs. These features, combined with the possibility to integrate QDs in optoelectronic devices, makes QDs particularly appealing for envisioned applications in quantum communication.
However, the structural properties of QDs are affected by unavoidable fluctuations, which make it difficult to obtain QDs with predefined electronic and optical characteristics. External perturbations are therefore needed to control the electronic structure of QDs after their fabrication.

In this talk I will present hybrid QD-based devices in which the semiconductor structures are integrated on top of piezoelectric actuators [1,2], which allow the strain in the semiconductor layer to be fine-tuned. This allows us on one hand to study in detail the effects produced by variable strains (up to about 0.2%) on the excitonic emission of single QDs and on the other to use strain to manipulate the electronic structure of QDs. By combining strain and electric fields in diode structures we are able to achieve unprecedented control on the properties of QDs. In particular we discuss wavelength-tunable single-photon light-emitting diodes [3].
[1] A. Rastelli et al. Phys. Stat. Solidi 249, 687 (2012)
[2] R. Trotta et al. Phys. Rev. Lett. 109, 147401 (2012)
[3] R. Trotta et al. Adv. Mater. 24, 2268 (2012)