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Berlin 2018 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 32: Quantum dots and wires: Optical properties II

HL 32.7: Talk

Wednesday, March 14, 2018, 16:45–17:00, A 151

Indirect (In,Al)As/AlAs quantum dots: Carrier spin dynamics and recombination — •Janina Rautert1, Sergey Nekrasov2, Timur Shamirzaev3, Jörg Debus1, Dmitri Yakovlev1,2, Yuri Kusrayev2, and Manfred Bayer1,21Experimentelle Physik 2, Technische Universität Dortmund, Germany — 2Ioffe Institute, St. Petersburg, Russia — 3Rzhanov Institute of Semiconductor Physics, Novosibirsk, Russia

Spin memory systems realized within a semiconductor application require structures that provide both long carrier lifetimes and spin relaxation times in the range of microseconds. Promising but little known candidates for that aim are (In,Al)As quantum dots (QDs) with an indirect band gap in the k-space. Here the direct band gap material is transformed to an indirect one by decreasing the QD size. Samples with a broad distribution of dot diameters allow the investigation of both types of QDs under selective excitation. Photoluminescence (PL) measurements in which the laser energy is tuned through the inhomogenously broadened dot ensemble show an increasing circular polarization degree up to 40% for indirect QDs speaking for a high spin relaxation time. Polarization degrees up to 90% can be reached by applying a small longitudinal field (mT-range) that suppress the nuclear spin fluctuations. In transverse magnetic fields however, the width of the Hanle curve corresponds to spin relaxation times of only a few nanoseconds. Therefore direct measurements of the spin dynamics and the exciton lifetime via time resolved PL are planned for the near future.

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