Photoluminescence and reflectivity measurements have been carried out on ${\mathrm{Zn}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{Mn}}_{\mathrm{x}}$Se solid solutions in the complete range of crystal compositions, 0≤x≤0.55. The features of the photoluminescence and reflectivity data near the band edge enabled us to determine values of the fundamental band gap as a function of Mn molar fraction x and temperature (8 K≤T≤300 K). The energy gap in crystals with compositions in the vicinity of the zinc-blende–wurtzite structural transition (0.2≲x≲0.3) exhibited a scatter of values, probably associated with the presence of various polytypes (as evidenced by transmission-electron-microscopy measurements). The dependence of $E_g$ on x is anomalous for 0≤x≤0.2, showing a minimum in the $E_g$ vs x curve. A simple model (in terms of second-order perturbation theory in s-d and p-d interactions) relates this minimum to a maximum observed in the magnetic susceptibility as a function of x. For samples with x≳0.35, the $E_g$ dependence on T shows an onset of an additional blue shift as the temperature is lowered below ∼150 K. This onset, though not reproduced by our simple calculation, appears to be also related to the presence of s-d and p-d interactions.

A strong temperature and magnetic field dependence of conductivity has been found in ${\mathrm{Cd}}_{0.95}$ ${\mathrm{Mn}}_{0.05}$Se. The effect appears to result from the influence of magnetic polarons and of the exchange-induced spin splitting on the quantum corrections to the conductivity of disordered magnetic metals.

We report on optical properties of CdTe self-assembled quantum dots (SADs) grown by molecular beam epitaxy on ZnTe. Formation of SADs was achieved by deposition of 1.5–2.5 monolayers of CdTe at a substrate temperature of 420 °C and by applying growth interrupts for few seconds in Cd flux. The resulting dots have a typical diameter of 2 nm and a sheet density of ${10}^{12} {\mathrm{cm}}^{\text{−2}}.$ At T=2 K the photoluminescence (PL) spectra consist of two emission lines. The high-energy line originates from excitonic recombination in a wetting layer while the low-energy emission PL band is assigned to recombination in SADs. The increase in temperature up to 70 K does not affect the SADs-related emission intensity. It shifts, however, the PL peak energy towards low energies and causes a significant narrowing of the PL linewidth, from 80 meV at 1.9 K to 50 meV at 130 K. The activation energy of the thermal quenching of SADs-related PL emission was found to be equal to 47 meV. This value is three times greater than the one observed in CdTe/ZnTe quantum wells, that is, 12–17 meV.

The mechanisms for generation of long-lived spin coherence in a two-dimensional electron gas (2DEG) have been studied experimentally by means of a picosecond pump-probe Kerr rotation technique. $\mathrm{Cd}\mathrm{Te}∕(\mathrm{Cd},\mathrm{Mg})\mathrm{Te}$ quantum wells with a diluted 2DEG were investigated. The strong Coulomb interaction between electrons and holes, which results in large binding energies of neutral excitons and negatively charged excitons (trions), allows one to address selectively the exciton or trion states by resonant optical excitation. Different scenarios of spin coherence generation were analyzed theoretically, among them the direct trion photocreation, the formation of trions from photogenerated excitons, and the electron-exciton exchange scattering. Good agreement between experiment and theory is found.

We provide an experimental evidence and a theoretical substantiation for a strong reduction of the $s-d$ exchange interaction between electrons and Mn-ion spins with increasing degree of the confinement in nanostructures of diluted magnetic semiconductors. By spin-flip Raman scattering a strong (up to $25\%$) reduction of the exchange parameter is observed in $(\mathrm{Cd},\mathrm{Mn})\mathrm{Te}/(\mathrm{Cd},\mathrm{Mn},\mathrm{Mg})\mathrm{Te}$ quantum well structures. As a responsible mechanism we suggest switching-on of the kinetic exchange for the conduction electrons with finite $\mathbf{k}$ vectors. Quantitative agreement between experimental data and calculations is achieved.