Regensburg 2010 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 37: Quantum Dots and Wires: Optical Properties III

HL 37.4: Vortrag

Mittwoch, 24. März 2010, 10:15–10:30, H15

Quantum efficiency and oscillator strength of site-controlled InGaAs quantum dots — •Ferdinand Albert¹, Christian Schneider¹, Søren Stobbe², Sven Höfling¹, Stephan Reitzenstein¹, Peter Lodahl², Lukas Worschech¹, and Alfred Forchel¹ — ¹Technische Physik, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany — ²DTU Fotonik, Department of Photonics Engineering, Technical University of Denmark, Ørsteds Plads 343, DK-2800 Kgs, Lyngby, Denmark

Quantum dots (QDs) are fascinating nanoscopic structures for future quantum information technology. Even though tremendous progress has been achieved in understanding their properties and integrating them into devices like single photon sources, their random position inhibits a large scale fabrication. Thus a great challenge is the precise control of their position. Recently several groups succeeded in the growth of site-controlled quantum dots (SCQDs), but a complete characterization of their intrinsic parameters is still missing. In the present work we apply a recently developed method of determining the oscillator strength and the quantum efficiency of QDs on In(Ga)As SCQDs by means of time resolved spectroscopy on samples with varying thickness of the capping layer [1]. The modification of the local density of optical states as a function of the distance between the SCQDs and the GaAs-air interface enables us to extract the radiative and nonradiative decay rates, from which we calculate a quantum efficiency of 47% and the oscillator strength of 10 for the excitonic transition in SCQDs.

[1] J. Johansen et al., Phys. Rev. B 77, 073303 (2008)