J. Krištofik

On space-charge-limited conduction in semi-insulating GaAs

Abstract We have measured the temperature dependence of Cr doped semi-insulating (SI) GaAs in planar and point contact configurations at various fields ranging between 10 and 10 6 V/m. In a planar configuration the transport is ohmic up to ∼ 10 4 V/m with an activation energy of ∼ 0.75 eV. At higher fields we have observed a space-charge-limited (SCL) transport with an activation energy of about 0.47 eV. In a point contact configuration a quasi-ohmic and a transitional region have been found, both having an activation energy of ∼ 0.47 eV. Such behaviour is in qualitative agreement with Lamperts theory of SCL conduction. Some deviations from this theory are accounted for by the existence of macroscopic screening length in SI-GaAs.

Selected topics related to the transport and superconductivity in boron-doped diamond

Abstract This contribution deals with a few topics closely related to the superconductivity in the heavily boron-doped diamond which are, in our opinion, not properly treated in the current literature. Attention is paid especially to the classification of metallic and insulating state, selection of pairing mechanism, limits of weak coupling approximation and to the influence of granularity on the superconducting transition.

On the d.c. conductivity in semi-insulating GaAs

Abstract We investigate the temperature dependence of electrical conductivity of SI-GaAs. We have shown that the surface conductivity obeys the Berthelot type of dependence, the bulk component, on the other hand, fulfills the Arrhenius dependence.

Amorphous nickel silicides prepared by magnetron co-sputtering

Abstract We have investigated properties of amorphous nickel silicides with different amount of metal ranging from 0 to ∼ 17 at. %. We discuss the transport mechanisms in silicides as well as the shift of the optical absorption edge with the Ni content.

The role of interface states in the evaluation of density of states from field effect measurements in dc-sputtered a-Si:H

Abstract We have succeeded in preparing FET type structure with a protective SiN x layer which enabled us to observe the largest field effect (FE) reported on dc-sputtered a-Si:H. The role of the interface states is demonstrated by a comparison of the density of states (DOS) deduced from the FE in structure with and without the protective layer and that from the analysis of space-charge-limited currents (SCLC) in heterojunction with a-Si:H prepared under the same conditions.

Application of the electrostatic Thompson–Lampard theorem to resistivity measurements

A method for measurement of resistivity of flat samples and thin layers complementary to the well-known van der Pauw technique has been proposed. The method is based on the application of the Thompson–Lampard theorem of electrostatics used in metrology for the realization of calculable capacitor, according to which a large variety of electrode systems can be designed. A prototypic electrode arrangement is shown on which the practical performance of the method was tested.

Amorphous-Crystalline Heterojunctions

Investigation of amorphous-crystalline (a/c) heterojunctions is useful both for the understanding of the fundamental device physics and for applications. In some cases it can also give important information about physical parameters of amorphous semiconductors.

Schottky barrier on n-GaAs formed by amorphous tungsten silicide

We have prepared amorphous tungsten silicides with different contents of tungsten by a.c. magnetron co-sputtering. For silicon to tungsten ratio smaller than 0.1, silicides have a metallic character. This material is suitable for Schottky contacts formation on n-GaAs.

On Expansion of a Spherical Enclosure Bathed in Zero-Point Radiation

In the present contribution a simple thought experiment made with an idealized spherical enclosure bathed in zero-point (ZP) electromagnetic radiation and having walls made of a material with an upper frequency cut-off has been qualitatively analysed. As a result, a possible mechanism of filling real cavities with ZP radiation based on Dopplers effect has been suggested and corresponding entropy changes have been discussed.

Analysis of experimental data on DX centres in GaAs1−xPx:S

Abstract The paper proves the applicability of three models of the DX centre to the experimental results obtained on the sulphur DX centre in GaAs1−xPx:alloys published in the previous paper. Two-level and three-level effective-mass-like models and a three-charge-state model are used. The solution of the charge neutrality eauation for different pressures and temperatures has given the temperature and pressure dependences of the resistivity and of deep-level transient spectroscopy peak amplitudes which are compared with the experimental data. The agreement is good for all three models. In the case of the third model the best agreement is obtained for U ≈ −20meV, that is a negative correlation energy.