Magnetic and vibrational Raman scattering from II-VI magnetic quantum wells: ZnTe/${\mathrm{Cd}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Mn}}_{\mathit{x}}$Se and ZnTe/MnSe

In a type-II multiple quantum well consisting of ZnTe/${\mathrm{Cd}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Mn}}_{\mathit{x}}$Se, the Raman shifts associated with the spin flip of donor-bound electrons in the ${\mathrm{Cd}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Mn}}_{\mathit{x}}$Se wells are significantly smaller than in bulk ${\mathrm{Cd}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Mn}}_{\mathit{x}}$Se of comparable x. This effect is ascribed to the decrease in the effective ${\mathrm{Mn}}^{2+}$ concentration as a result of the penetration of the donor electron wave function into the nonmagnetic barrier. Raman electron paramagnetic resonance is of ${\mathrm{Mn}}^{2+}$ also observed in these type-II quantum wells, whose resonance enhancement is associated with spatially direct interband transitions from states above the barrier for holes to the quantum confined electronic states. We also report the observation of confined longitudinal-optical phonons and folded acoustic phonons in strained ZnTe/MnSe multiple quantum wells. In this heterostructure we observe an unusual combination mode involving vibrational excitations in two different layers (ZnTe and MnSe).