INFLUENCE OF MAGNETIC-FIELD ON BLUE ANTI-STOKES LUMINESCENCE OF ZNSE-CR CRYSTALS

The results of photoluminescence and magneto-luminescence studies of c hromium doped ZnSe crystals are presented for blue colour shallow dono r-shallow acceptor pair photoluminescence, with a zero phonon line at 2.692 eV. This donor-acceptor pair photoluminescence is observed under photo-excitation with photon energies smaller than the emission energ y (anti-Stokes luminescence) and dominates in the photoluminescence sp ectrum of ZnSe:Cr at the excitation energy about 2.41 eV and for tempe rature T < 20 K. A quantum efficiency of this anti-Stokes luminescence is relatively large. It is of about 10(-3) at 0 T and increases with increasing magnetic field up to 7 T at temperature T = 2 K. We relate the intensity of the anti-Stokes luminescence to a non-equilibrium con centration of photo-excited Cr+ ions and propose that the rate of spin -dependent recombination of Cr+ ions with free holes (decreases with i ncreasing magnetic field) is responsible for the observed increase in the anti-Stokes luminescence intensity at higher magnetic fields.