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Ionic semiconductor CdF2 with a record band-gap, 7.8 eV, is of extraordinary interest for high temperature spin-optoelectronics and spintronics. The goal of this work is to study the ballistic transport of the spin-polarized holes by varying the value of the Rashba spin-orbit interaction (SOI) in the p-type quantum well prepared on the surface of the n-CdF2 bulk crystal.
The p+-CdBxF2-x-n-CdF2 planar structures have been prepared in frameworks of the Hall geometry by the short-time diffusion of boron from the gas phase. The forward branches of the CV characteristics reveal not only the CdF2 gap value, 7.8 eV, but also the high temperature ballistic transport of holes. Besides, the low energy part of the forward CV characteristic exhibits the spectrum of the tunnelling current that is related to the energy positions of the two-dimensional hole subbands in the p-type ultra-narrow quantum well. The mesoscopic fluctuations of the conductance, 2e2/h, are also observed, which are evidence of the hole quantum subbands caused by the Andreev reflection in the barriers confining the p-type quantum well. These findings confirm the hypothesis that the p-type CdBxF2-x nanostructures are self-assembled inside the CdB2 superconductor shells. The Hall measurements demonstrate the high mobility of the two-dimensional gas of holes in the quantum well plane: 8.3x104cm2/Vs which allow the Shubnikov - de Haas oscillations at T=300K . The studies of the dependencies of the static magnetic susceptibility on the external magnetic field value show that the 2D gas of holes is spin-polarized by the s-f exchange interaction due to the presence of ittrium in the n-type CdF2substrate as well as a result of the Andreev reflection. Finally, the findings of the CV characteristics in the plane of the p-type quantum well that are due to the variations of the Rashba SOI are shown to be evidence of the spin Hall effect and the spin transistor effect, with the amplitude of the oscillations close to e2/h. |