Phonon conductivity of GaAs

A modified Holland's and three-phonon processes having different temperature dependences in the varius temperature ranges have been used to analyse the lattice thermal conductivity of GaAs. A very good agreement with the experimental results has been obtained     

Photoinduced effects and metastability in amorphous semiconductors and insulators

Amorphous semiconductors, being intrinsically metastable in nature, exhibit a wide variety of changes in their physical properties, particularly when photoinduced using bandgap illumination. This article reviews the photoinduced phenomena exhibited by amorphous semiconductors such as amorphous hydrogenated silicon (and other tetrahedrally coordinated materials) and chalcogenide glasses. Features exhibited in common by all types of amorphous semiconductors, whether in the experimentally observed photoinduced metastability or the theoretical models used to account for such behaviour, are stressed.     

Plasmons in semiconductors and insulators: A simple formula

Based on the dielectric function of an excitonic system, a simple model dielectric function is constructed. The high energy zero of this function yields the plasma frequency, and is given by: (hω_x)² = (hω_f)² + E_x² where ω_f is the free electron plasma frequency and E_x the lowest exciton energy. It is argued that this formula is valid for both, Frenkel and Wannier excitons, and comparison is made with experiments on a variety of crystals, ranging from InSb to Ar. In all cases, surprisingly good agreement is found.     

Phonon conductivity of deformed lithium flouride crystals

The Callaway model has been applied to investigate the effect of (1) vibrating dislocation scattering, (2) static dislocation scattering, and (3) point-defect scattering of phonons on the thermal conductivity of deformed LiF crystals. It is found that the point-defect scattering of phonons does not produce any appreciable thermal resistance but that the other two scattering processes have a very strong influence on the thermal conductivity. The correction term due to three-phonon normal processes is also found to be significant.     

Three-dimensional topological insulators in I-III-VI2 and II-IV-V2 chalcopyrite semiconductors

Using first-principles calculations within density functional theory, we investigate the band topology of ternary chalcopyrites of composition I-III-VI2 and II-IV-V2. By exploiting adiabatic continuity of their band structures to the binary 3D-HgTe, combined with direct evaluation of the Z2 topological invariant, we show that a large number of chalcopyrites can realize the topological insulating phase in their native states. The ability to host room-temperature ferromagnetism in the same chalcopyrite family makes them appealing candidates for novel spintronics devices.     

Phonon fluorescence of metal films and semiconductors stimulated by intense laser radiation

The kinetic equations have been obtained to describe both electron-impurities and electron-phonon interaction when the system is subjected to the intense electromagnetic radiation. Frequency distribution of the generated acoustic phonons is calculated for the case of the degenerate electron system.     

Self-energy corrections to the local density band structure of semiconductors and insulators

A formalism is proposed that allows an efficient computation of the exchange-correlation functional including the nonlocal exchange and dynamical screening correctly. In combination with LDA band structures this functional leads to remarkably good results for semiconductors and even wide gap insulators. The model furthermore provides a qualitative understanding of electronic many-body effects.     

Thermal conductivity of GaS and GaSe layered semiconductors

This paper reports on the results of experimental investigations into the thermal conductivity of GaS and GaSe layered semiconductor crystals in directions parallel and perpendicular to the crystal layers in the temperature range 5–300 K. Specific features of the thermal conductivity of these crystals are analyzed.     

Microwave conductivity studies on some semiconductors

The cavity perturbation technique is employed for the characterisation of semiconductors at microwave frequency for its conductivity. Temperature variation of microwave conductivity studies provide the information regarding the band gap, scattering parameter and impurity ionization energy. Change in the real part of the dielectric permittivity with conductivity indicates the change in the momentum relaxation time.     

Laser-induced conductivity of semiconductors at low temperatures

We consider the negative conductivity of electrons in semiconductors excited by a picosecond laser pulse at low temperatures, due to the inelastic electron-phonon collisions. For the first time, the dependence of the deformation potential on the phonon wave number is taken into account. This dependence significantly changes the region of negative electron conductivity as a function of the phonon temperature. The text was submitted by the authors in English.     

Phonon thermal conductivity of amorphous selenium doped by germanium

The thermal conductivity of the amorphous semiconducting system Se-Ge in the temperature range of 100 to 300°K was measured. The Debye model was used for the analysis of the experimental values and the calculated mean free path of phonons was related to the size of the basic structure units of the selenium glass. The shift of the thermal conductivity of amorphous selenium doped with germanium was explained by means of the increase of the velocity of sound observed together with the occurrence of the covalent bond Se-Ge between the basic structure units of the studied amorphous system.