Circularly polarized emission from ensembles of InAs/GaAs quantum dots
2011 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 110, no 1, 013510- p.Article in journal (Refereed) Published
We present a low-temperature micro-photoluminescence (mu-PL) study of ensembles of InAs/GaAs quantum dots (QDs) with respect to its circular polarization (rho(c)) for a manifold of experimental conditions such as single or dual laser excitation, different excitation energies (h upsilon(ex)), varying excitation powers (P(ex)) of both lasers, and with or without an external magnetic field (B(ext)). It is demonstrated that an essential rho(c) (less than= 40%) could be recorded depending on P(ex), even at B(ext) = 0 for h upsilon(ex) exceeding the PL energy of the wetting layer (E(WL)), while rho(c) remains negligible for h upsilon(ex) less than E(WL). To explain the data obtained, a model is developed according to which a nuclear magnetic field (B(N)) is created in the QDs by spin-polarized electrons. The B(N) plays a crucial role in the preservation of the electron spin, which otherwise effectively relaxes due to the presence of the anisotropic electron-hole exchange interaction (omega(ex)). The application of an additional infra-red laser gives rise to a population of excess holes in the QDs, thus producing positively charged excitons. In this case, omega(ex) = 0 and accordingly, rho(c) approximate to 40% at B(ext) = 0 is recorded, even for excitation with h upsilon(ex) less than E(WL).
Place, publisher, year, edition, pages
American Institute of Physics , 2011. Vol. 110, no 1, 013510- p.
Engineering and Technology
IdentifiersURN: urn:nbn:se:liu:diva-69808DOI: 10.1063/1.3599853ISI: 000292776500027OAI: oai:DiVA.org:liu-69808DiVA: diva2:433555
Original Publication: Evgenii Moskalenko, L.A. Larsson and Per-Olof Holtz, Circularly polarized emission from ensembles of InAs/GaAs quantum dots, 2011, Journal of Applied Physics, (110), 1, 013510. http://dx.doi.org/10.1063/1.3599853 Copyright: American Institute of Physics http://www.aip.org/2011-08-102011-08-082013-05-07