S. F. Gabibov

Experimental determination of the constants of absolute volume deformation potentials at band edges in semiconductors

A method is proposed for determining the constants of absolute volume deformation potentials at edges of the conduction and valence bands in semiconductors. This method is based on (i) the volume-concentration effect, (ii) the concept that the energy of deep-lying strongly localized impurity centers does not depend on the hydrostatic pressure, and (iii) the use of experimental data on the electrical resistivity and Hall coefficient. For Ge, GaAs, InAs, and InSb semiconductors, the constants of absolute volume deformation potentials at edges of the conduction and valence bands are determined from our results and data available in the literature.

Effect of pressure on the electronic spectrum of indium arsenide

Based on the dependences of the Hall coefficient and the resistivity of n- and p-InAs and p-InAs〈Mn〉 bulk crystals on hydrostatic pressures up to 9 GPa at 77 and 300 K, the evolution of the energy spectrum of electrons upon isotropic contraction of a crystal lattice is studied. Intervals between the energy levels of shallow, deep, and deep resonance impurity centers and between the edges of intrinsic bands, and the pressure coefficients for these intervals, were determined.

The electronic spectrum and electrical properties of germanium with a doubly charged gold impurity on both sides of the L1 ⇄ Δ1 intervalley transition for uniform pressures of up to 7 GPa

The dependences of resistivity ρ and the Hall coefficient R<0 on hydrostatic pressure P(P≤7 GPa) were studied at room temperature in Ge:(Au, Sb) with a partially populated (at 0 K) doubly charged Au level EAu2− on both sides of the intervalley transition that occurred for P≅2.8 GPa. In terms of the two-band model, the baric dependences ρ(P) and R(P) and also the similar dependence of the Hall mobility with allowance made for interband scattering were calculated; the results agree satisfactorily with the experimental data. Characteristic parameters of the charge carriers and the baric coefficients for energy gaps between the edges of the L1 and Δ1 subbands in the conduction band and the EAu2− level were determined. It was ascertained that the position of the energy level for a doubly charged gold impurity in germanium is fixed with respect to the valence-band top. The density-of-state effective mass of electrons in the (100) minimum of the conduction band of germanium was determined experimentally (and using the known values of the band parameters) and was found to be mdΔ=62/3(m∥m⊥2)1/3=1.05m0. It is shown that Ge:Au2− can be used to check the uniformity of pressure of up to 10 GPa.

The nature of 'heavy' electrons in the p-HgTe zero-gap semiconductor

To interpret the low-temperature features of the electron transport in the p-HgTe zero-gap semiconductor, the model is suggested, according to which, the “heavy” electrons are the electrons for the conduction band localized in the wells of the fluctuation potential. The experimental data on the temperature, magnetic field, and baric dependences of the Hall coefficient R(T, H, P) and electrical conductivity ρ0(T, P) in lightly doped, moderately compensated, and heavily doped p-HgTe samples are analyzed.

Using Hydrostatic Pressure for Evaluating the Effect of a Fluctuating Potential on the Energy Spectrum of Charge Carriers in Crystalline Semiconductors

As known [1, 2], doped compensated semiconductors (in which the concentration of free charge carriers is small compared to the concentration of ionized impurities) exhibit smooth, large-scale fluctuations of random potential with certain characteristic amplitudes ( γ ). The role of this chaotic potential increases with decreasing temperature, while at a fixed temperature it grows under the action of pressure as the free carrier concentration decreases [3]. It is important to develop a method for evaluating the effect of the chaotic potential on the energy spectrum of charge carriers and to assess the correctness of relations obtained for defect-free crystals so as to provide a quantitative analysis of experimental data in each particular case. It should be noted that the pressure coefficients of the energy gaps in semiconductors are virtually pressure-independent at not very high pressures. Moreover, the pressure-induced changes of the deepest minima e Γ , e L , and e X in the conduction bands of various semiconductors (IV, II‐VI, III‐V, IV‐VI, and II–IV–V 2 ) are also approximately the same [4‐8]. Previously, the pressure coefficients of the e Γ , e L , and e X extrema relative to the values in absolute vacuum were determined [5] based on a concept according to which the energy of deep strongly localized states in some semiconductors is independent of the uniform (hydrostatic) pressure.

Thermal-physical and thermoelectric properties of solids near the polymorphic and superconducting transitions

The relationships are presented for the effective thermal conductivity and thermoelectric power coefficients near the superconducting and polymorphic phase transitions. The relationships are verified using the experimental data obtained for porous media saturated with a fluid. The experimental data obtained for the high-temperature superconductor YBa2Cu3Ox (x = 6.8, 6.9) and n-InAs are analyzed.

Concept of mobility threshold: The Ioffe-Regel rule

Metal-insulator phase transitions in solids that are not related to a change in the crystal lattice symmetry have been discussed using experimental data on the properties of lightly and heavily doped three-dimensional crystalline semiconductors. The minimum metallic conductivities and mobilities, the critical concentrations of main impurities and majority charge carriers, and the compensation coefficients of the n-GaAs, p-Ge, and p-CdSnAs2〈Cu〉 compounds have been presented. It has been shown that experimental data agree with the concept of mobility threshold.

Thermoelectric Properties of a Ferromagnetic Semiconductor Based on a Dirac Semimetal (Cd 3 As 2 ) under High Pressure

The pressure dependences of thermal emf (a parameter that ranks among the most sensitive to phase transformations) are studied for the purpose of identifying baric phase transitions in the 10–50 GPa interval in the Cd3As2 + MnAs (44.7% MnAs) structure formed by ferromagnetic MnAs granules in a semiconductor Cd3As2 matrix.

On metal-insulator electronic phase transitions in semiconductors

Some aspects of the problem of metal-insulator electronic phase transitions in semiconductors, which were not adequately studied previously, are examined in this paper. The issues considered are the effect of the hybridization between the resonance quasi-bound impurity states and the band continuum states on the transition, the effect of the uniform pressure on the nature of the transition, specific features of the metal-insulator transormation in the system of hydrogen-like impurities in the intermediate doping region in lightly doped narrow-gap and wide-gap semiconductors, and Anderson localization in heavily doped semiconductors. Minimum metallic conductivities under the conditions of Mott and Anderson transitions in p-CdSnAs2:Cu are determined. Phase diagrams are discussed.

Electron Metal-Dielectric Phase Transitions in Semiconductors under Pressure

The effect of uniform pressure on the character of metal-dielectric transitions in compensated weakly- and highly doped semiconductors (WHDCS) is considered. The influence of hybridization of resonance quasilocalized impurity states with band continuum states on the transition is shown. Minimum metallic conductivities in p-CdSnAs2 are determined for Mott and Anderson transitions. Special features of the metal-dielectric transformation in weakly-doped narrow- and high energy-gap semiconductors are discussed for the case of hydrogen-like impurities. Anderson localization in WHDCS is also considered. Phase diagrams are presented.