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MBE Growth and Optical Study of Magnetic CdMnTe Quantum Dots

Grzegorz Karczewski 

Polish Academy of Sciences, Institute of Physics, al. Lotników 32/46, Warszawa 02-668, Poland


In bulk semiconductors and in semiconductor quantum wells the carrier spin relaxation time is short - in the order of tens picoseconds. Since in quantum dots (QDs) the carriers are confined in all three dimensions the scattering processes are strongly suppressed resulting in spin-relaxation times of the order of nanoseconds. This makes the QDs particularly good suited for gaining the ability to control and manipulate spin states in semiconductor structures.

We report recent results of spectroscopy of magnetic CdMnTe QDs. The investigated structures have been grown by MBE. We focused our study on QDs containing only few Mn ions. The insight into properties of these structures was obtained by performing a high spatial resolution PL measurement in a magnetic field. The spectra are fully circular polarized already at 2T. In order to obtain precise information about the size and the number of Mn ions inside a particular dot we compare the evolution of a corresponding PL-line in an external magnetic field to the theoretical simulations in terms of the muffin tin model. In particular, we present magnetic field dependence of two lines, of which one is coming from low energy part of the spectrum and the other from the high energy part. We found that there are from 5 to 25 Mn ions coupled to excitons in our QDs depending on the size of the dot. We also estimated the QDs size distribution in our ensemble. Due to particular stability of the exciton magnetic polarons in CdMnTe QDs, where the localization of electrons and holes is comparable to the magnetic exchange interaction, the optically induced spin alignment persists to temperatures as high as 160 K.


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Presentation: Invited oral at E-MRS Fall Meeting 2006, Symposium E, by Grzegorz Karczewski
See On-line Journal of E-MRS Fall Meeting 2006

Submitted: 2006-06-09 12:20
Revised:   2009-06-07 00:44