Microsecond Lifetime of Exciton Spin Polarization in (In,Al)As/AlAs Quantum Dots
T. S. Shamirzaev1, D. Dunker2, J. Debus2, D. R. Yakovlev2,3, K. S. Zhuravlev1, M. Bayer3
1Rzhanov Institute of Semiconductor Physics, Siberian Branch, Russian Academy of Sciences, pr. Akademika Lavrent’eva 13, Novosibirsk, 630090 Russia
2Experimentelle Physik 2, Technische UniversitВЁat Dortmund, Dortmund, 44221 Germany
3Ioffe Physical Technical Institute, Russian Academy of Sciences, ul. Politekhnicheskaya 26, St. Petersburg, 194021 Russia
Keywords: quantum dots, exciton, spin relaxation
Abstract
The time of spin relaxation of excitons in (In,Al)As/AlAs quantum dots with an indirect bandgap and type-I band alignment is determined by measuring the dynamics of photoluminescence circular polarization induced by a magnetic field B. The spin relaxation time τS increases with decreasing magnetic field in proportion to B−5; its value is ~40 µs in a magnetic field of 6 T at a temperature of 1.8 K. As the temperature T increases in a magnetic field of 7T, the value of τS decreases as T−1.1. The character of the dependences of τS on the magnetic field and temperature evidences that spin relaxation of excitons is provided by a process with participation of one acoustic phonon.
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