[en] The Hall coefficient Rsub(H), conductivity sigma and thermoelectric power α, of heavily doped InSb have been measured at pressures up to 25 kbar and temperatures 4.2-500 K. The samples were doped with S, Se and Te up to the concentration 10¹⁹cm^-3. It was observed that Rsub(H)(p) strongly increases at high pressure. Such a dependence was interpreted as due to the deionization of resonance states of impurities and to transfer of electrons from GAMMA band to minimum L. For pressures and temperatures at which the deionization was observed the anomalous pressure dependence of thermoelectric power α, and Hall mobility μsub(H) were observed. α(p) passes through a deep minimum whereas μsub(H)(p) changes strongly its slope. The observed anomalies suggest the direct influence of the resonance scattering. (Auth.)

No abstract available

[en] Week localization corrections to conductivity of two-dimensional electron gas are studied by measurements of magnetic field dependence of the conductivity in GaInAs quantum wells. We observed that, when presented as a function of the normalized magnetic field (x=B/B_tr where B is the magnetic field, B_tr=h/4eτD, D is the diffusion constant and τ is momentum relaxation time), different samples show very similar high field behaviour. A theoretical description is developed that allows one to describe in a consistent way and low field behaviour. The theory predicts universal (B^-1/2) behaviour of the conductivity correction for all 2D systems in high field limit (x>1). Low field behaviour depends strongly on spin and phase relaxation mechanisms. Comparison of the theory with experiment confirms the universal behaviour in the high field limit and allows one to estimate the spin and phase relaxation times for different GaInAs quantum wells. (author)

[en] First, theoretical calculations of electron mobility and thermoelectric power in n-type InSb are reported at liquid nitrogen and room temperatures. All the scattering mechanisms of importance in InSb are taken into account. The calculations based upon a variational solution of the Boltzmann equation are compared with experimental results over the whole available range of electron concentrations. Good agreement between theoretical and experimental results is obtained using the value of deformation potential constant C = 14.6 eV. Secondly, both, experimental and theoretical investigations are made of mobility in InSb under hydrostatic pressure at 77 K within a wide range of electron concentrations. The smallest electron concentrations obtained by freezing the conduction electrons on the metastable states are of order of 1x10¹² cm^-3. Also for those smallest concentration it is possible to describe theoretically the dependence of mobility on the hydrostatic pressure using the same set of parameters as previously, and assuming some compensation of donors by acceptors. (author)

[en] Comprehensive studies of the electrical properties of Mg-doped bulk GaN crystals, grown by high-pressure synthesis, were performed as a function of temperature up to 750 degree C. Annealing of the samples in nitrogen ambient modifies qualitatively their resistivity values ρ and the ρ(T) variation. It was found that our material is characterized by a high concentration of oxygen-related donors and that the charge transport in the studied samples is determined by two types of states, one of shallow character (Mg-related state, E_A∼0.15eV), and the second one much more deep, E₂∼0.95eV (above the valence band). Depending on the effective concentration of either states, different resistivities ρ can be observed: lower resistivity (ρ<10⁴Ωcm at ambient temperature) in samples with dominant E_A states and very high resistivity (ρ>10⁶Ωcm at ambient temperature) in samples with dominant E₂ states. For the first type of samples, annealing at T_ann<500 degree C leads to a decrease of their resistivity and is associated with an increase of the effective concentration of the shallow Mg acceptors. Annealing of both types of samples at temperatures between 600 and 750 degree C leads to an increase of the deep state concentration. The presence of hydrogen ambient during annealing of the low-resistivity samples strongly influences their properties. The increase of the sample resistivity and an appearance of a local vibrational mode of hydrogen at 3125 cm-1 were observed. These effects can be removed by annealing in hydrogen-free ambient. [copyright] 2001 American Institute of Physics

[en] Measurements have been performed of the Hall coefficient versus temperature in the range of 50 to 90 K under different hydrostatic pressures up to 5 kbar for undoped n-InSb samples. Different curves were obtained after different cooling treatments of the sample. In order to interpret the results a deep level with a degeneracy factor g=2 and the presence of some number of fully ionized compensating acceptors were assumed

[en] We measured Hall concentration n in InGaP:Si epitaxial layers grown by MBE as a function of pressure P up to 2GPa and temperature T from 77 to 300 K. We interpreted our results in terms of the broad distribution of impurity states resonant with the conduction band. From the low-temperature n(P) dependence we can directly obtain the total density of impurity states around Fermi level (ρ(E_F). The Fermi level can be shifted with respect to impurity states by applying pressure and by using samples with different n. In this way we obtain ρ(E) in a wide energy range. We discuss the possible reasons for the observed broad distribution of ρ(E). (author)

No abstract available

[en] The existence of localized 'resonant' state in GaAs doped with Ga₂O₃ is revealed. It lies about 0.4 eV above the conduction band minimum and moves down with a rate of 16 meV/kbar. At temperatures T<110 K various metastable occupations of this state can be created either via persistent photoconductivity effect or by a special pressure cooling cycle. (author) 4 refs., 4 figs

[en] Usually the multi-layer technique is applied for the growth of p-type gallium nitride (GaN) films, and the active p-type layer is deposited on an n-type GaN buffer layer. In the present paper, the electrical transport phenomena (conductivity and Hall effect) have been studied in p-GaN/GaN homo-structures grown on a sapphire substrate. Two types of GaN buffer layers were used: a silicon-doped one and another strongly compensated by magnesium. We demonstrate that in the analysis of the electrical conduction phenomena the parallel conduction in the n-type buffer layer cannot be neglected, and it manifests itself in the studies of a conduction process as a function of temperature and as a function of electric field intensity