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The results of studies of the spectral and kinetic characteristics of the photoluminescence of photonic crystals formed on the basis of structures with self-assembled Ge(Si) nanoislands are reported. The experimentally observed enhancement of the photoluminescence-signal intensity of the nanoislands in the spectral range 1.1–1.6 μm due to interaction with the radiative modes of photonic crystals in the vicinity of the Γ point of the Brillouin zone and the effect of such interaction on the probability of radiative recombination in Ge(Si) nanoislands are considered.

The results of studies of the luminescence properties of two-dimensional photonic crystals formed on the basis of silicon structures with self-assembled Ge(Si) nanoislands are reported. The possibilities of substantially enhancing the luminescence response of the active medium (Ge(Si) nanoislands) in the wavelength range 1.2–1.6 μm are shown for such structures. The specific features of the luminescence response of a photonic crystal in the vicinity of the Γ point of its Brillouin zone are studied. It is shown that, along with the broadband response characteristic of the radiative modes of photonic crystals, high-Q resonances, for which the Q factor exceeds 103, can also be observed in such structures. The last-mentioned resonances are observed in a certain range of lattice parameters of photonic crystals.

On the example of synthetic single crystal diamond with negatively charged nitrogen-vacancy center (NV)—center, we have experimentally reviled the changes in the polarized spectrum of the first-order Raman scattering due to the presence of nitrogen impurities. It has been found the appearance of rather intense spectra of the Brillouin zone-center optical phonons in an unpredictable crossed polarization of the incident and scattered light, while in the previously reported Raman data it was observed only in parallel polarization of the incident and scattered light. Such a recovery of Raman intensity is prescribed to the change of the local symmetry from the point group Oh to C3v in accordance with the results of Raman scattering polarization rules based on conclusions of the group theory. The data make obvious also the observation of the strong in-coming resonance with the nitrogen NV 0 center electronic transition.

The relaxation of holes from excited states of boron acceptors in diamond with the emission of two optical phonons is studied theoretically. To describe the wave function of acceptor states, an electron-like Hamiltonian with an isotropic effective mass is used. The wave function of the ground state is determined by the quantum-defect method. The probability of the transition is calculated in the adiabatic approximation. It is assumed that the phonon dispersion law is isotropic and the phonon frequency is quadratically dependent on the wave-vector modulus, with the maximum and minimum frequencies ωmax and ωmin at the center and boundary of the Brillouin zone, respectively. A high sensitivity of the probability of the transition to the characteristic of phonon dispersion ωmax – ωmin is revealed, especially for the transition with the energy ET in the range 2ℏωmin ≤ ET 1012 s–1) in the “resonance” range ℏωmin + ℏωmax ≤ ET ≤ 2ℏωmax.

The field and temperature dependences of the magnetization (magnetic fields B ≤ 7.5 T, temperatures T = 2.0–75 K) of samples from a Pb1–x–ySn x V y Te (x = 0.08, y = 0.01) single-crystal ingot synthesized by the Bridgman–Stockbarger method. It is established that the sample magnetization contains two main contributions, notably, the paramagnetism of vanadium ions and diamagnetism of the crystal lattice. The field and temperature dependences of the magnetization are approximated by the sum of modified Brillouin functions corresponding to the paramagnetic contributions of vanadium in two different charge states and the diamagnetic contribution linear in terms of field. The concentrations of vanadium ions in two different magnetic states and the character of their variation along the ingot are determined within the scope of the alloy’s electronic-structure rearrangement because of doping. The results are compared with the data of X-ray fluorescence microanalysis and the results of studying the galvanomagnetic properties of the samples.

The field dependences of the magnetization (temperatures T = 2.0–70 K, magnetic fields B ≤ 7.5 T) of the samples from a single-crystalline Pb1 – yFe y Te ingot (y = 0.02) grown by the Bridgman method are studied. It is established that the sample magnetization contains several major contributions such as the paramagnetism of iron ions, diamagnetism of the crystal lattice, and the contributions of charge carriers and clusters of iron atoms. The field dependences of the paramagnetic contribution of iron ions and the contribution of clusters of iron atoms are approximated by theoretical dependences based on the Brillouin and Langevin functions, respectively. The average concentrations and magnetic moment of clusters as well as the total magnetic momentum of clusters in the volume unit in the samples upon increasing the impurity concentration along the ingot are determined.

This work addresses the issue related to the electronic transport in the III–V ternary material Ga0.5ln0.5Sb using Monte Carlo method. We investigated the electronic motion in the three valleys Γ, L, and X of the conduction band. These three valleys are isotropic, non-parabolic and centred on the first Brillouin zone. In our study, we included scatterings with ionised impurities, acoustic and polar optical phonons, as well as, intervalley and intravalley interactions. We discussed the electronic transport characteristics at the stationary and the transient regimes in function of temperature and electric field.

Ab initio calculations of the electronic spectrum, deformation electron density, and phonon frequencies at the center of the Brillouin zone of the CdAs2 tetragonal compound are carried out in the context of the density-functional method. It is established that the crystal is an indirect-gap semiconductor with a band gap of ~1 eV, which is in good agreement with well-known optical and electrical experimental data. The features of chemical bonding in the crystal are studied. The features are defined by the fact that As atoms form spiral chins of covalent As–As bonds, whereas Cd–As bonds are ionic-covalent. The ab initio calculated phonon frequencies are compared with the frequencies calculated in the Keating model and with experimental data; the partial contributions of Cd and As atoms are analyzed.

It is demonstrated theoretically that the interaction of gapped 2D materials (gapped graphene and transition metal dichalchogenide monolayers) with a strong high-frequency electromagnetic field (dressing field) crucially changes the band structure of the materials. As a consequence, the renormalized band structure of the materials drastically depends on the field polarization. Particularly, a linearly polarized dressing field always decreases band gaps, whereas a circularly polarized field breaks the equivalence of band valleys in different points of the Brillouin zone and can both increase and decrease corresponding band gaps. It is shown also that a dressing field can turn both the band gaps and the spin splitting of the bands into zero. As a result, the dressing field can serve as an effective tool to control spin and valley properties of the materials in various optoelectronic applications.

The localization of the transitions in the bulk of the Brillouin zone that form the main structures in the spectra of the imaginary part of the permittivity in the range up to ~7 eV for III–V semiconductors (AlSb, GaSb, InSb, and InAs) is determined using electron density functional theory. It is established that intense transitions occur not only in the vicinity of the high-symmetry axes of the Brillouin zone, but also in some specific large volumes of the irreducible part of the Brillouin zone.

In the context of density functional theory, the phonon density of states and phonon dispersion are calculated for ZnGa2Se4. The temperature dependence of the heat capacity of ZnGa2Se4 in the temperature range 5–400 K is obtained. The calculated frequencies and symmetries of phonon modes in the center of the Brillouin zone are in good agreement with experimental data obtained by Raman spectroscopy and infrared spectroscopy.

It is demonstrated that the 6H-SiC natural superlattice has two simultaneously electroluminescence channels in the terahertz range: narrow lines at frequencies of 1.6–2.3 THz and broader lines at frequencies of about 3.25 THz. The first channel is formed by transitions between the localized states of the Wannier-Stark ladder in the Bloch oscillation mode in the first conduction miniband at point M of the hexagonal Brillouin zone. The second channel is probably caused by transitions between Wannier-Stark ladders formed by electric-field mixing of degenerate states of the conduction band at point K of the hexagonal Brillouin zone. The conduction-band minimum at point K is higher than that at point M by 100–200 meV.

The Raman spectra of CdGa2S4x Se4(1 − x) alloys (x = 0.1, 0.2, … 0.9) are studied. Both the singlemode and double-mode behavior of optical phonons are observed in CdGa2S4x Se4(1 − x) alloys. The observed optical mode at 138 cm−1 is independent of the composition. It seems likely that this mode is the “breathing mode” and is caused by atomic motion in the anion sublattice relative to vacancies. It is shown that the high-frequency modes of symmetry B 1(LO, TO) and B 2(LO, TO) are caused by the in-phase motion of atoms in the anion sublattice along the tetragonal axis c relative to trivalent Ga atoms. The doubly degenerate symmetry modes E 1(LO, TO) and E 2(LO, TO) are caused by the in-phase motion of atoms in the anion sublattice relative to trivalent Ga atoms of the cation sublattice in the xy plane (dipole 2Ga–4C), where C is S, Se. The optical symmetry modes B 3(LO, TO) and B 4(LO, TO) are associated with the motion of atoms in the anion sublattice relative to Cd atoms along the tetragonal axis c. The doubly degenerate modes E 3(LO, TO) and E 4(LO, TO) are associated with the motion of atoms in the anion sublattice relative to Cd atoms (dipole Cd–4C). The low-frequency modes B 5(LO, TO) and E 5(LO, TO) are the analogs of acoustic phonons at the edge of the Brillouin zone of sphalerite.

Sets of fundamental optical functions in the energy range of 0–40 eV for longitudinal indirect interband transitions in graphite with a quasi-gap up to 2.6 eV have been determined for the first time. Their structure and parameters depend strongly on the electron wave vector transfer q. The nature of the peaks and shoulders of these functions is explained within the model of theoretical shifted bands for four electron wave vector transfers q in a volume characteristic electron-energy losses for the Γ-P direction in the Brillouin zone. The calculations were performed on the basis of the known experimental volume characteristic electron-energy loss spectra of graphite in the range of 0–40 eV for |q| = 0.00, 0.375, 0.625, and 1.00 A−1 using a special software package.

It is shown that a study of the dependence of impurity-related resonant first-order Raman scattering on the frequency of excitation light makes it possible to observe the dispersion of polar optical and acoustic branches of vibrational spectrum in hexagonal InN within a wide range of wave vectors. It is established that the wave vectors of excited phonons are uniquely related to the energy of excitation photon. Frequencies of longitudinal optical phonons E1(LO) and A1(LO) in hexagonal InN were measured in the range of excitation-photon energies from 2.81 to 1.17 eV and the frequencies of longitudinal acoustic phonons were measured in the range 2.81–1.83 eV of excitation-photon energies. The obtained dependences made it possible to extrapolate the dispersion of phonons A1(LO) and E1(LO) to as far as the point Γ in the Brillouin zone and estimate the center-band energies of these phonons (these energies have not been uniquely determined so far).

The ab initio density functional method with using pseudopotentials has been applied to calculate the electronic and vibrational spectra of the LiN2 and NaPN2 crystals, with optimization of their structure. The specific features of the crystal structure (highly compressed chalcopyrite) and composition of these crystals manifest themselves in the qualitative similarity of their band spectra and chemical bonding to those of chalcopyrite as well as in some substantial distinctions. The second valence band exhibits four branches instead of two branches, as in chalcopyrite crystals, and involves contributions of the p-states of the P and N atoms rather than the s states of the Group-III cations in the I-III-VI2 chalcopyrite compounds. The top of the valence band is at the side points of the Brillouin zone, the bottom of the conduction band is in the center of the Brillouin zone, and the absorption edge corresponds to the indirect band gap. The contributions of alkali metals to the vibration spectra are significant in the region of low-frequency modes; phosphorus and nitrogen make significant contributions to the modes in the high-frequency region, which is due to the prominent covalent component of bonding between these atoms.

Using the method of linear response, vibrational spectra and densities of states of GaP and AlP crystals and monolayer GaP/AlP superlattices are calculated. Phonon modes of (GaP)n(AlP)m superlattices with various numbers of monolayers are calculated for the center of the Brillouin zone. The obtained results are compared with the Raman scattering data and the effect of nonideality of the interface on phonon frequencies is discussed.

A model is developed to analyze numerically the electrical properties and the steady-state (limiting) position of the Fermi level (Flim) in tetrahedral semiconductors irradiated with high-energy particles. It is shown that an irradiated semiconductor represents a highly compensated material, in which Flim is identical to 〈EG〉/2, where 〈EG〉 is the average energy gap between the conduction band and valence band within the entire Brillouin zone of the crystal. The experimental values of Flim, the calculated values of 〈EG〉/2, and the data on the electrical properties of irradiated semiconductors are presented. The chemical trends controlling the variation in the quantity Flim in groups of semiconductors with the similar types of chemical bonding are analyzed.

The temperature dependence of the energies of some characteristic energy extrema at the Γ, L, K, M, A, and H high-symmetry points of the Brillouin zone and the energies of the main interband transitions in hexagonal modifications of ZnS, ZnSe, ZnTe, and CdTe are calculated using the empirical pseudopotential method. The effect of the temperature dependence of electron-phonon interaction on the energy-band structure is taken into account using the Debye-Waller factors, and the effect of lattice linear expansion is described using the temperature dependence of the linear expansion coefficient. The features of the temperature dependence of electron levels, interband transitions, and temperature coefficients are discussed in detail. Possible applications of the obtained results are considered.

The method of empirical pseudopotential was used for the first time for the calculation of the temperature dependence of the energy extrema at the Г L, K, M, A, and H high-symmetry points of the Brillouin zone for hexagonal modifications of gallium and aluminum nitrides, as well as of the energies of the main inter-band transitions between these extrema. The effect of the temperature dependence of electron-phonon interaction on the band structure of the crystal was described using the Debye-Waller factors, and the contribution of the linear expansion of the lattice was taken into account via the temperature dependence of the linear expansion coefficient. The features of the temperature dependence of the energy levels and interband transitions were analyzed in detail. Comparison of the calculations with the experimental data in available publications has shown good agreement.

An increase in the electrical conductivity is observed in the Pb1−x SnxTe:In/BaF2 films subjected to laser radiation with a wavelength λ=336.8 μm (the frequency of ∼0.9×1012 Hz) at the liquid-helium temperature; this increase cannot be accounted for by a heating of the sample. The observed photosignal-relaxation time does not exceed the RC time constant of the measurement circuit (this time constant amounts to fractions of seconds) and is much shorter than in the case of illumination within the fundamental absorption band of Pb1 − x SnxTe:In. The results obtained relate to an increase in the low-frequency permittivity ɛ as a result of excitation (by photons of the submillimeter region) of one or two transverse optical phonons in the center vicinity of the Brillouin zone at the branch responsible for the ferroelectric phase transition. This circumstance brings about an increase in the space-charge-limited injection current that flows from the contacts without a generation of free charge carriers in the bulk.

The low-temperature photoluminescence and Raman scattering in CdSe/ZnSe nanostructures with individual CdSe inserts of 1.5 and 3.0 monolayers in nominal thickness were studied. The energy position of the photoluminescene band is governed by interdiffusion of Cd and Zn into the insert regions, whereas the shape of this band is controlled by strong interaction of localized excitons with optical phonons in the Zn1−xCdxSe solid-solution insert. Multiphonon processes of excitonic relaxation with involvement of acoustic phonons at the Brillouin zone edges are also important. The results obtained are interpreted in the context of a model for the effective excitonic mobility edge.

The temperature dependences of significant energy extrema at the high-symmetry points Γ, X, L, K, M, A, and H of the Brillouin zone in the cubic and hexagonal modifications of SiC, as well as the energies of the main interband transitions at these points, were calculated for the first time by the empirical-pseudopotential method. The effect of the temperature dependence of the electron-phonon interaction on the crystal band structure was taken into account via the Debye-Waller factors, and the contribution of the linear expansion of the lattice was accounted for via the temperature dependence of the linear-expansion coefficient. The special features of the temperature dependences of the energy levels and of energies of the interband and intraband transitions are analyzed in detail. The results of the calculations are in good agreement with the known experimental data on the characteristics of SiC-based p-n structures operating in the breakdown mode. For example, the temperature coefficient of the energy of the X 1c –X 3c transition, which is responsible for the narrow violet band in the breakdown-electroluminescence spectra of reverse-biased p-n junctions, was found to be significantly smaller than the temperature coefficients for the interband transitions (from the conduction to valence band). This fact is quite consistent with the experimental curve of the temperature coefficient of the emission spectrum, which has a minimum in the same wavelength range.

Absorption spectra of nitrogen-doped n-type 6H-SiC crystals were studied for two orientations of the light wave electric field (E) relative to the optical axis (C), E ∥ C and E ⊥ C, within the range from the near-infrared region to the fundamental band. For E ∥ C, a weak absorption band peak at 2.85 eV was investigated for the first time. All the absorption bands observed are attributed to donor (nitrogen) photoionization, as a result of which electrons are transferred to the conduction-band upper minima that correspond to different critical points of the Brillouin zone. A combined analysis of the new data obtained in this study, the previous experimental results concerning photoionization of nitrogen, and theoretical data on 6H-SiC conduction band structure made it possible to refine the arrangement and symmetry of the additional conduction-band extrema in the Brillouin zone.

The pseudopotential method has been used to optimize the crystal lattice and calculate the energy band spectra for iron, ruthenium and, osmium monosilicides. It is found that all these compounds are indirect-gap semiconductors with band gaps of 0.17, 0.22, and 0.50 eV (FeSi, RuSi, and OsSi, respectively). A distinctive feature of their band structure is the “loop of extrema” both in the valence and conduction bands near the center of the cubic Brillouin zone.

Galvanomagnetic effects (B⩽7 T) in electron-irradiated n-and p-type Pb1−xSnxSe (x⩽0.03) alloys (T≈300 K, E=6 MeV, Φ⩽5.7×1017 cm−2) in the neighborhood of a pressure-induced insulator-metal transition (P⩽18 kbar) are discussed. The field dependences of the Hall coefficient calculated in terms of the two-band model are in satisfactory agreement with the experimental data, and the main parameters of the charge carriers in irradiated alloys are determined. It is shown that there is an increase in the hole concentration in the metallic phase under the action of pressure, associated with the motion of the energy bands at point L of the Brillouin zone, and that electrons overflow from the valence band into the band Et1 of resonance states induced by electron irradiation; the parameters of this band are estimated.

The energy spectra of chalcogen impurities in germanium are studied by photoconductivity, optical absorption, and photoluminescence. The previously found excited states of these impurities are identified. The observed excited states of tellurium (Te+) and selenium (Se+) ions are shown to be associated with the Γ and L points of the germanium Brillouin zone, respectively.

The structure of the valence band at the Γ point of the Brillouin zone of Cu(In,Ga)Se2 films is investigated on the basis of interference spectrophotometry data and an analysis of the structure of edge absorption within the framework of the quasicubic model of valence-band p-d hybridization in chalcopyrite compounds. The fundamental parameters of the quasicubic model associated with splitting of the valence band under the action of the tetragonal lattice field (Δcf), the spin-orbit interaction (Δso), and the degree of adulteration (hybridization) of the upper p-levels of the chalcogen by copper d states in Cu(In,Ga)Se2 chalcopyrite films are determined. The dependence of the direct allowed transitions E A , E B , E C on the composition of CuInxGa1−xSe2 solid solutions (for 0⩽x⩽1) is established.

The oscillations caused by optical interband electron transitions at the point L of the Brillouin zone of bismuth are studied in the temperature range of 77–280 K and magnetic fields up to B=22 T. It is shown that the method of simulation of the experimental line shape allows one not only to refine the band parameters of the material, but also to obtain detailed information about physical reasons for the specific features observed in the experimental magneto-optical spectra.