Electron and holegfactors measured by spin-flip Raman scattering in CdTe/Cd1−xMg

Abstract

We report resonant spin-flip Raman scattering measurements in CdTe/Cd 1Ϫx Mg x Te single quantum wells with xϭ0.15, 0.26, and 0.5 as well as in Cd 1Ϫx Mg x Te alloys with xϭ0, 0.15, and 0.5. Effective g factors of electrons and heavy holes are measured as a function of the quantum well width (18Ϫ100 Å͒ and the angle of the magnetic field with respect to the growth axis. The electron g factors in quantum wells are between the values for bulk CdTe (g e ϭϪ1.644Ϯ0.005) and Cd 0.85 Mg 0.15 Te (g e ϭϪ0.802Ϯ0.005). We show that the change in the energy gap induced by the quantum confinement of the carriers provides the dominant contribution to the electron g factor in quantum wells. A large g factor anisotropy for conduction electrons is observed. It is shown that this anisotropy depends on the splitting between light-and heavy-hole states. The experimentally determined g factors are in good agreement with theoretical predictions. ͓S0163-1829͑97͒06128-6͔

Positively versus negatively charged excitons: A high magnetic field study of CdTe/Cd1−xMgxTe quantum wells

“…Its value is measured by pump-probe Kerr rotation and the negative sign is taken in analogy to the data of bulk CdTe. 41 Three dependencies for heavy-holes are evaluated from the Zeeman splittings of Fig. 12(c); the styles of the corresponding lines are the same.…”

Linear polarization of the photoluminescence of quantum wells subject to in-plane magnetic fields

“…At a fixed magnetic field, the Raman shifts of the Mn and ESF lines do not depend on θ, since the g-factors of the 3d electrons of manganese and of the conduction band electrons are both to a good approximation isotropic [ 11 ]. On the other hand, the Raman shifts of the HSF and XSF depend strongly on θ, as shown in Fig.10.…”

“…The field-dependence of the ESF Raman shift is reasonably well described by a Brillouin function [ 9 ] plus the intrinsic conduction band Zeeman splitting with the following parameters: effective temperature T + T 0 = 3.8K (higher than the bath temperature of 1.5K because of antiferromagnetic coupling effects at the high Mn concentration of the barrier [ 12 ]); effective paramagnetic Mn concentration experienced by the quantum well electrons x = 0.0034; s-d exchange constant N 0 α = 0.22 eV, and conduction band g-factor for the quantum well of -1.3; this latter is altered from the intrinsic CdTe conduction band g-factor value of -1.67 [ 13 ] because of quantum confinement effects [ 11,14 ]. Several alternative sets of fitting parameters can be found but we have chosen the set most consistent with the previous work cited here.…”

“…As the magnetization increases, the spin splittings first increase linearly and then acquire a superlinear contribution. We note that the slower saturation of HSF and XSF could in principle arise from an intrinsic valence band Zeeman splitting h B g H µ but a fit including such a term to this data requires g h ~ 2.1 to 2.2, which is implausibly large [ 11,14 ].…”

Temperature Dependence of Exciton and Trion States in CdTe Quantum Well at High Magnetic Fields

“…Thus the total difference between the observed and the real energy positions of the singlet and triplet trion states would equal ∆E = g e µH. Taking into account that the g-factor of the electron in CdTe is equal to -1.56 [4] one can calculate ∆E = 2.3 meV at 26 T magnetic field. This means that the real difference between the singlet and triplet energy levels is not 3 meV as observed in experiment but only about 0.7 meV.…”