R. R. Gałązka

Near band-gap optical nonlinearities and bistability in Cd1−xMnxTe

Abstract Strong thermally induced self-focusing of laser beam near the band-edge in Cd1−xMnxTe with 0

Electroluminescence and positive magnetoresistance near the Curie–Weiss temperature in the Zn1−xMnxTe light emitting devices

The light emitting devices (LEDs) based on the p-Zn1−xMnxTe bicrystals have been fabricated. The Zn1−xMnxTe LEDs produce red and green emission originated from the internal d-shell transitions of the Mn2+ ions and the donor-acceptor-pairs recombination, respectively. The presence of the acceptor bound magnetic polarons and their clusters in the Zn1−xMnxTe crystals near the Curie–Weiss temperature was observed. It induces a critical behavior of the magnetic field dependence of the green emission intensity and a positive magnetoresistance in the Zn1−xMnxTe LEDs.

Magnetoresistive switching and highly polarized electroluminescence from semimagnetic semiconductor bicrystals Zn1−xMnxTe

The Zn1−xMnxTe bicrystals grown by the high-pressure Bridgman method exhibit magnetic-field-sensitive current-voltage characteristics. The threshold voltage of avalanche breakdown decreases by 40% as the magnetic field increases from 0 to 14 T. In the postbreakdown regime, the Zn1−xMnxTe bicrystals emit an intense red and green electroluminescence. Under magnetic field, the green emission exhibits a high degree of circular polarization which reaches 0.95 and 0.78 at 1.8 K and 4.2 K, respectively. The relation between the photon energy of the green emission and the threshold voltage has been studied.

CdTe-Based Semimagnetic Semiconductors

Publisher Summary CdTe is a component of the best known and widely investigated semimagnetic semiconductor. There also exist other CdTe based SMSs such as CdHgMnTe, CdZnMnTe, CdMnTeSe, CdCoTe, CdCrTe, CdFeTe, and not so well known as CdMnTe, but also investigated and showing interesting properties. SMSs are the group of solids at the interface between semiconductors and magnetic materials. SMSs also referred to as diluted magnetic semiconductors, are semiconductor-based solid solutions where a part of cations are replaced by transition metals or rare earth elements. Crystallographic structure of semiconductor is conserved; the lattice constant is a function of composition. From a magnetic point of view SMS is a disordered magnetic material, since magnetic atoms are randomly distributed in the cation sublattice of semiconductor compound. Both bulk and low-dimensional structures made of CdTe based SMSs have contributed immensely to the progress in physics and technology of semiconductors as a whole, and being one of the most important members of the family of semimagnetic semiconductors gave strong input to the foundation of the recently vividly developing field of spin-based semiconductor electronics: “spintronics.”

Shubnikov-De Haas effect in Hg1−xMnxSe:Fe

Fe donor level in HgSe is degenerate with the conduction band and lies about 210 meV above its edge [1] (see, lower part of Fig. 1a). This fact gives rise to several unusual properties of Fe doped HgSe [see, e.g., 2]. For low iron concentration (N Fe < N Fe * ≈ 4.5 × 1018cm −3) all resonant donors are ionized to Fe3+ state (as shown schematically in upper part of Fig. la). The properties of the crystal at low temperatures are then similar to those of HgSe doped with, e.g., gallium [3,4]. When the iron concentration exceeds N Fe * the neutral and ionized donors coexist (mixed valence regime — see, Fig. 1b). In such circumstances the system is able to lower its energy by redistribution of electrons between ionized and neutral donors, which leads to spatial correlations of positions of ionized donors [5]. Ultimately a “charge superlattice” of ionized donors can be formed. In consequence, the low momentum transfer scattering processes, important in the case of the scattering by charged centers (dominant mechanism in HgSe at LHe temperatures), are exduded. The electron mobility and the Dingle temperature TD achieve then anomalous values (respectively, high and low). On the other hand, the resonant character of the donors could open an additional very effective scattering channel — the resonant scattering. However, as pointed out in [6], formation of the Coulomb gap [7] in one electron d-band density of states (caused by inter — site repulsion) suppresses this mode of scattering.