Magnetooptical study of CdSe/ZnMnSe semimagnetic quantum-dot ensembles with n-type modulation doping

Abstract

Magnetic and polarization investigations of the photoluminescence and resonant electron spin-flip Raman scattering in ensembles of self-organized CdSe/ZnMnSe semimagnetic quantum dots with n-type modulation doping are carried out. It is demonstrated that exciton transitions contribute to the photoluminescence band intensity, along with the transitions of trions in the singlet state. In the Hanle-effect measurements, negative circular polarization in zero magnetic field is observed, which is related to the optical orientation of a trion heavy hole. The lifetime and spin-relaxation time of a heavy hole are estimated as ≤3 and ≤1 ps, respectively. Such short times are assumed to be due to Auger recombination with the excitation of an intrinsic transition in a Mn2+ ion. Investigations of the photoluminescence-maximum intensity and shift in a longitudinal magnetic field at the σ−σ+ and σ−σ− polarizations reveal the pronounced spin polarization of electrons. Under resonant excitation conditions, a sharp increase in the photoluminescence-band maximum intensity at σ− excitation polarization over the σ+ one is observed. The Raman scattering peak at the electron spin-flip transition is observed upon resonant excitation in a transverse magnetic field in crossed linear polarizations. This peak is shown to be a Brillouin function of a magnetic field.