Berlin 2018 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 32: Quantum dots and wires: Optical properties II

HL 32.7: Vortrag

Mittwoch, 14. März 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 Yakovlev^1,2, Yuri Kusrayev², and Manfred Bayer^1,2 — ¹Experimentelle 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.