Controlling the electronic structure of quantum dots via stress and electric fields

Description

Optically active semiconductor quantum dots (QDs) can be made as nanoinclusions of a low energy bandgap material 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. The structural properties of self-assembled QDs are affected by unavoidable fluctuations, which make it difficult to obtain QDs with electronic and optical properties which meet (sometimes very stringent) requirements for their use in advanced quantum optics experiments. Post-growth methods are therefore becoming increasingly important to fine-tune the optical properties of QDs. In this talk we will discuss QD-based devices in which the semiconductor structures are integrated on top of piezoelectric actuators [1]. This combination allows us to study in detail the effects produced by variable strains (up to about 0.2%) on the excitonic emission of single QDs and to add a “tuning knob” to QDs. In particular, by combining stress with electric fields we are able to: (i) obtain frequency-stabilized, electrically pumped sources of single photons at predefined wavelengths [2] and (ii) restore the excitonic level degeneracy in arbitrary QDs, which is required for their use as entangled-photon-pairs sources [3]. Possible future extensions and applications will be discussed. References [1] A. Rastelli, et al. "Controlling quantum dot emission by integration of semiconductor nanomembranes onto piezoelectric actuators", Phys. Status Solidi B 249, 687 (2012) [2] R. Trotta, et al. "Nanomembrane Quantum-Light-Emitting Diodes Integrated onto Piezoelectric Actuators", Adv. Mater, 24, 2668 (2012) [3] R. Trotta, et al. "Universal Recovery of the Energy-Level Degeneracy of Bright Excitons in InGaAs Quantum Dots without a Structure Symmetry", Phys. Rev. Lett. 109, 147401 (2012)

Period	03 Jul 2013
Event title	The 16th International Symposium on the Physics of Semiconductors and Applications (ISPSA-XVI)
Event type	Conference
Location	Korea, Republic ofShow on map