High Electric Field Conduction Research Articles

High-electric field conduction phenomena in poly-2-chloro-p-xylylene/poly-p-xylylene composite thin films

The high-field currents in poly-p-chloro-xylylene (PCPX) thin films are due to hole injection from anode metal and collision ionization. PPX thin films showed the negative temperature dependence of high-field currents. Since the chlorine atoms in PCPX thin films act as carrier scattering centers, high-field currents in PCPX thin films are suppressed in the low-temperature region. This paper discusses the high-field currents of PCPX/PPX composite thin films; these films are PCPX thin films (d 200 nm). They were strongly suppressed at room temperature, but not at low temperature. Therefore, PCPX/PPX composite thin films showed a remarkable negative temperature dependence of high-field currents. High-field currents were suppressed more in PCPX (60 nm)/PPX (230 nm) composite thin film than in PCPX (130 nm)/PPX (230 nm). This can be explained by the suppression of the hole injection from anode by homo space charge at the interface between PCPX/PPX.

High-field electrical conduction in m Hgl2

The electrical and dielectric properties of illuminated Hgl2 were studied at room temperature under various a.c.-signal amplitudes in the frequency range 1 Hz to 10 kHz. Below 40 H, We real part of the dielectric constant, ɛ′,was found to vag slightly with voltege for low electric fields (E 103V cm−1), σ ∝ exp [C(E/ɛ′)1/2], whereC is e constant. Above 40 Hz, this variation was in good agreement with the behaviour of the bulk, resistance of the crystal. Such behaviour is discussed in the view of Richardnon-Schottky and Poole-Frenkel conduction mechanisms, which seem to be operative in Hgl2 at room temperature.

High-field electrical conduction in thin films of polyethylene

The voltage-current characteristics of thin film metal-polyethylene-copper structures in which copper is used as a top electrode are studied. The samples made with thermally vacuum-evaporated polyethylene and having a top electrode of copper show space-charge-limited conduction, whereas the samples made from blown polyethylene show the Poole-Frenkel type of high-field conduction. The observed space-charge-limited conduction is belived to be due to the copper atoms diffused into the polyethylene during the deposition process. Les caracteristiques tension-courant des couches minces de metal-polyethylene-cuivre pour les echantillons avec le cuivre en position superieure, sont etudiees. Les echantillons fabriques par evaporation sous vide du polythylene montrent un processus de conduction limite par la charge d'espace, et les echantillons fabriquees du polyethylene prepares par un processus de soufflage montrent evidence pour l'effet Poole-Frenkel aux champs eleves. La conduction limitee par la charge d'espace est montree en consequence de la diffusion des atomes de cuivre pendant le processus de deposition.

Stark ladders and high-field electrical conduction in impure semiconductors

The high-field electrical conduction in impure semiconductors has been treated, taking into account the conditions which would favour the occurrence of Stark ladders (SL). Some results of the authors previous treatment (Roy and Mahapatra 1983) for high-field electrical conduction in semiconductors have been used for the purpose. The carrier concentration in impure semiconductors has been obtained by considering the mechanisms of (i) Poole-Frenkel (PF) effect and (ii) field emission (FE) or tunneling. The aspects studied are the variation of current density with field and the relative influences of the PF effect and FE on the carrier concentration. The results are discussed critically, especially in the light of the experimental findings of Maekawa (1970).

A study of high-field electrical conduction and of optical absorption of SiO/SnO2 thin films

Presentation des caracteristiques courant-tension, entre 300 et 398 K, d'un systeme Cu-SiO/SnO 2 -Cu. Le comportement est non lineaire au-dela de 0,2 V. La limite d'absorption optique est mal definie et caracteristique des materiaux amorphes

Temperature dependence of the transient high-field electrical conduction in evaporated thin potassium iodide films

The temperature dependence in the range 215-343K of the high-field electrical conduction in evaporated thin potassium iodide films has been studied for 1 V applied voltage, covering a range from microseconds to several hours. The results show that the universal dielectric response is valid separately in two or three regions for temperatures lower or higher than 269K respectively. Change in the temperature of the films has a different effect in each region on the transition probability, which is associated with the hopping mechanism.

Transient high-field electrical conduction in evaporated thin potassium iodide films

Transient high-field electrical conduction in evaporated thin potassium iodide films has been studied as a function of the applied voltage at room temperature, covering a time range from microseconds to several hours. The results show that the universal dielectric response is valid separately in three regions. The electrical conduction is achieved through the hopping mechanism. The transition probability, associated with the hopping mechanism in each region, is affected differently by the applied voltage.

High electric field conduction and magnetoresistance in a-Ge at 4.2 K

Experimental results are presented for the electric conductivity and magnetoresistance of evaporated and annealed films of a-Ge. When the samples are subjected to a strong electric field at 4.2 K, In σ ∞ − F 1 4 law is clearly observed. By using the slopes of T −1 4 and F −1 4 plots, the radius and density of localised states at the Fermi level are determined independently. Magnetoresistance has been measured in the F −1 4 region for magnetic field up to 60 kG, and is found to be always positive. The empirical expression is obtained, dependent on the annealing conditions.

The high field electrical conduction of β rhombohedral boron measured by a single voltage pulse

The current-voltage characteristics of a β rhombohedral boron crystal (Wacker-Chemie) were measured between 96 and 294 K with a single voltage pulse. It seems that the measurement with a single pulse can reduce the build-up of space charge, because switching phenomena were not observed until 60 kV cm −1, at which field a discharge along the surface took place. From 1 to 60 kV cm −1 only non-ohmic currents were observed over the whole temperature range. At low temperatures the conduction may be explained by an activationless hopping mechanism at high electric fields.

Instabilities during high-field electrical conduction in solids

Measurements of the time and voltage dependence of dc and ac currents in insulators and semiconductors and the evaluation of results of other authors on corresponding measurements using metallic samples reveal that critical power densities Nk1≈10−8 W/mm3 and Nk2≈10−5 W/mm3 separate three different ranges of charge transport loading of solids in the frequency range 0⩽f⩽50 Hz. The loading state of a solid is described macroscopically by the average electric power density and microscopically by the local value of the power density j↘⋅E↘. In semiconductors and insulators electrical breakdown or transition to a strongly localized and highly conducting state is unavoidable if an overcritical power density N≳10−5 W/mm3 is supplied. This locally quite limited and highly conducting state exists in the prebreakdown range wherein Nk2<N<Nfusion. It is related to the Ovshinsky effect in amorphous semiconductors. Usually the current density, continuity, and Poisson equations are used to describe charge transport within a solid. In order to complete this description it is proposed that power density N=j↘⋅E↘ must be considered.

High field electrical conduction in some organic charge-transfer complexes

The semiconductivity of perylene–chloranil and perylene–2,3-dichloro-5,6-dicyano-p-benzoquinone complexes has been investigated in the temperature range 150 to 345 K with applied electric fields up to 107 V m–1. Results obtained from the analysis of generalized current against temperature plots suggest that the high field conduction mechanism is a bulk process between Poole–Frenkel type centres. Values have been derived or estimated for such electronic parameters as the charge carrier concentration and mobility, and the energies and concentrations of the dominant donor and trapping sites. An extrinsic conduction mechanism involving the M+A– complex, where M is an impurity metal such as Na, is developed to describe the semiconductivity of these and some other charge-transfer complexes whose electrical characteristics have been reported in the literature.

Electrical conduction in reactively sputtered tantalum oxide thin films

High-field electrical conduction over a temperature range of 303-363 K has been studied in sandwich structures of Al/Ta2O5/Al and Al/Ta2O5/Ta in the thickness range 400-900 nm. The oxide film was produced by reactively sputtering a tantalum target in a mixture of argon and oxygen. No marked rectification was observed in the samples and it was observed that the conduction process bore strong resemblance to either a Poole-Frenkel or a Schottky mechanism, the results showing a definite lowering of the activation energy for the conduction process with field. Detailed analysis of the data suggest an electrode-limited mechanism such as that suggested by Schottky.

Determination of conduction anisotropies in semiconductors

A simple theoretical method has been developed which gives the correct magnitude and form of the high electric field conduction anisotropies found experimentally in many-valley cubic semiconductors. This approach is applicable to any of the many-valley cubic semiconductors such as n-type Ge, Si, AlSb, GaAs, GaP, PbTe, and PbSe upon insertion of the appropriate parameters. A knowledge of the band structure and the assumption of randomizing scattering processes are used to calculate the longitudinal and transverse components of the current density as a function of crystallographic orientation. The results contain a phenomenological parameter which is determined by measuring j vs. E for a particular direction. The measurement of this parameter, which is dependent on temperature and carrier concentration, substitutes for a detailed calculation of the distribution function.

On a characteristic effect for high-frequency and high-electric field conduction of small polaron in ferromagnetic semiconductors

A theoretical model for high-frequency or non-ohmic small polaron conduction in ferromagnetic semi- conductors provides a method of determination of the s-d exchange coupling constant.

Gunn Effect in InAs Under Hydrostatic Pressure

We have studied the high electric field conductivity of n-type InAs at pressures up to 29 kbar. Carrier multiplication due to impact ionization of valence band electrons is the predominant phenomenon at lower pressures, while the Gunn effect is observed at higher pressures. Above about 25 kbar no carrier multiplication is observed below the threshold electric field for Gunn effect. The bulk negative differential conductivity underlying the Gunn effect is presumed to be due to the transferred carrier mechanism. From the change in character of the high-field transport near 25 kbar, and from some recently published studies on the In1-xAlxAs alloy system, we eliminate the subsidiary minima involved in the carrier transfer to lie about 1.2±0.05 eV above the top of the valence band at atmospheric pressure, and to have L1 symmetry. The results are compared with an earlier report of Gunn effect in InAs under uniaxial stress.

High Field Electrical Conduction and Dielectric Breakdown of Mica

High Field Electrical Conduction and Dielectric Breakdown of Mica