The Effect of Hydrostatic Pressure and Cationic Vacancy on the Electronic and Magnetic Properties of the ZnSe:T Crystals (T = Ti, V, Cr, Mn, Fe, Co, Ni)

Abstract

The parameters of the spin-polarized electronic energy spectrum of ZnSe:T crystals (T = Ti, V, Cr, Mn, Fe, Co, Ni) are studied on the basis of a 2 × 2 × 2 supercell built on the basis of a ZnSe unit cell with a sphalerite structure. The supercell contains 64 atoms, with one Zn atom replaced by one transition 3d element T. The first stage of this study is to calculate in the ideal material ZnTSe parameters of electronic energy bands, dependent on the external hydrostatic pressure. At the second stage, the effect of pressure on the parameters of the electronic energy spectrum in the ZnTSe materials is investigated, taking into account the Zn vacancy. The calculations were performed using the Abinit program. For a better description of strongly correlated 3d electrons of the element T, a hybrid exchange-correlation functional PBE0 with an admixture of the Hartree-Fock exchange potential was used, in which the self-interaction error of these electrons is removed. Based on the obtained spin-polarized electron densities of states, the magnetic moments of the supercells were also determined. A significant effect of pressure on the parameters of electronic energy zones was revealed. So, the ideal ZnTiSe material at zero pressure is a metal for both spin values, but under pressure it becomes a semiconductor. The same material with a point defect, i.e. a vacancy at the site of the Zn atom, exhibits semiconductor properties for both spin orientations at zero pressure. It was found that vacancies radically change the parameters of electronic energy bands. The magnetic moments of the supercell, as integral values of the spin-polarized densities of electronic states, also reflect these changes. Thus, in ZnTiSe material without defects, the magnetic moments of the supercell are 1.92, 2.0 and 2.0, at pressures 0, 21 and 50 GPa, respectively, while in the same material with a vacancy, the corresponding values are 0.39, 0.02 and 0.36. The ideal ZnVSe material at zero pressure is also a metal for both values of the spin moment, but in the presence of a cationic vacancy it is characterized by a pseudogap because the Fermi level is localized in the upper part of the valence band. Ideal ZnFeSe and ZnNiSe crystals are characterized by similar dependences of the electronic energy parameters on the pressure, for both spins. However, the same materials with a cationic vacancy are characterized by the Fermi level immersed in the valence band for a spin up.

Calculation of the Total Current Generated in a Tunnel Diode Under the Action of Microwave and Magnetic Fields

“…As research on the properties of semiconductor materials and devices based on them continues, various tunneling models for p-n junction diodes have been presented. Since the electrical properties of semiconductor materials mainly depend on the state of impurity atoms in their volume, when choosing an alloying element, one should pay attention to their physicochemical parameters [11][12][13][14]. At a conference in Berlin in 1989, Herks presented a new model that related the rate of Shockley-Reed-Hall (SRH) recombination and zone-tunneling in the opposite direction [10].…”

“…From the works presented above and from the available literature data, it can be seen that the effect of a magnetic field and an electromagnetic field with an ultrahigh frequency on a tunnel diode has not been studied enough. Based on this, the purpose of this work is to develop a new model for calculating the total current for a tunnel diode, taking into account the impact on the tunnel diode of a magnetic field and a microwave electromagnetic field [12][13][14].…”