Optical orientation and alignment of excitons in direct and indirect band gap (In,Al)As/AlAs quantum dots with type-I band alignment

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Authors	RAUTERT Janina SHAMIRZAEV Timur S. NEKRASOV S. V. YAKOVLEV Dmitri R. KLENOVSKÝ Petr KUSRAYEV Yu. G. BAYER Manfred
Year of publication	2019
Type	Article in Periodical
Magazine / Source	Physical Review B
MU Faculty or unit	Faculty of Science
Citation
Web	https://journals.aps.org/prb/abstract/10.1103/PhysRevB.99.195411
Doi	http://dx.doi.org/10.1103/PhysRevB.99.195411
Keywords	(InAl)As/AlAs;kvantove tecky;rekombinacni procesy
Description	The spin structure and spin dynamics of excitons in an ensemble of (In,Al)As/AlAs quantum dots (QDs) with type-I band alignment, containing both direct and indirect band gap dots, are studied. Time-resolved and spectral selective techniques are used to distinguish between the direct and indirect QDs. The exciton fine structure is studied by means of optical alignment and optical orientation techniques in magnetic fields applied in the Faraday or Voigt geometries. A drastic difference in emission polarization is found for the excitons in the direct QDs involving a ?-valley electron and the excitons in the indirect QDs contributed by an X -valley electron. We show that in the direct QDs the exciton spin dynamics is controlled by the anisotropic exchange splitting, while in the indirect QDs it is determined by the hyperfine interaction with nuclear field fluctuations. The anisotropic exchange splitting is determined for the direct QD excitons and compared with model calculations.
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