Regensburg 2004 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 50: Quantenpunkte und -dr
ähte: Optische Eigenschaften III

HL 50.3: Vortrag

Freitag, 12. März 2004, 11:30–11:45, H14

Selective optical charging of self-assembled InGaAs quantum dots — •Miro Kroutvar, Yann Ducommun, Jon J Finley, Max Bichler, and Gerhard Abstreiter — Walter Schottky Institut, Technische Universit"at M"unchen, Am Coulombwall 3, 85748 Garching, Germany

Charge and spin excitations in individual quantum dots (QDs) have been proposed as QBITS for implementation of quantum logic. One of the main challenges for these applications is the selective creation of electrons in such systems and control of their spin degree of freedom. We present a QD charging device which enables to optically generate single charges and potentially spins in sub-ensembles of self-assembled InGaAs QDs. The device consists of a single layer of InGaAs QDs embedded within the intrinsic region of a GaAs Schottky photodiode. The charge storage mechanism relies on selective exciton ionization following resonant optical generation. Our results demonstrate unambiguously selective charging with extremely long (>25 µs) charge storage lifetimes at low temperatures (10K). Analysis of the energy and temperature dependence of the charge storage signal permits investigation of the role of exciton-phonon coupling during the QD resonant absorption process. In addition, thermally-activated redistribution of resonantly stored charge among the QD ensemble is identified to be the cause of a time-dependent loss of spectral selectivity at elevated temperatures. Our storage device enables to probe directly resonant carrier excitation processes and potentially electron spin dynamics in micro-ensembles of semiconductor QDs.