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Electrical Spin Injection of Spin-Polarized Electrons into InAs QDs from Fe
Contacts
A. Petrou 1 , M. Yasar 1 , M. Diaz-Avila 1 , G. Kioseoglou 2,3 , C.H. Li 2 , B.T. Jonker 2
1 SUNY at Buffalo, Buffalo N.Y
2 Naval Research Laboratory, Washington, DC 20375
3 Materials Science and Technology, University of Crete, Heraklion, Crete
*petrou@buffalo.edu
Spin-polarized electrons from Fe contacts were injected into zero-dimensional InAs quantum dots (QDs) where they
recombine with unpolarized holes. Using standard MBE growth techniques, the QD density was reduced resulting in
uniform dot-size distribution. The broad electroluminescence (EL) observed previously in high QD density LEDs [1]
is replaced by distinct excitonic features associated with the atomic-like conduction and valence band s-, p-, d-, and f-
shells of the QDs. When the diode current was increased, the higher energy shells became populated as the lower shells
became occupied. The circular polarization P of the emitted light was studied as function of applied magnetic field B,
current, and temperature. The circular polarization of the EL intensity maxima is almost zero for completely filled
shells. These peaks are identified as due to excitonic emission that involves electrons and holes within the same shell.
The circular polarization of the EL spectrum exhibits well defined strong maxima in-between the EL peaks. These
maxima have been identified as due to negatively charged excitons in which the participating electrons come from
consecutive shells [2]. The P versus B plots of these maxima confirms spin injection from Fe.
[1] Li et al. Appl. Phys. Lett. 86, 132503, (2005)
[2] Ware et al, Phys. Rev. Lett. 95, 177403 (2005)
Work at SUNY was supported by ONR (N000140610174) and NSF (ECS0524403).
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