Current Conduction Model Research Articles

Current conduction models in the high temperature single-electron transistor

Single-electron transistor drain current is studied as a function of the temperature. A current conduction model based on the physical properties of the tunnel junctions is proposed to explain the discrepancies observed at high temperature between the experimental data and Monte Carlo simulations. The extension of the model includes a thermionic and a field assisted emission component. A demonstration of this approach is presented for a metallic single-electron transistor characterized up to 430 K.

A compact analytical current conduction model for a depletion-mode n-type nanowire field-effect transistor with a bottom-gate structure

A compact analytical current conduction model for depletion-mode n-type nanowire field-effect transistors (NWFETs) with a bottom-gate structure is introduced. Our model includes the current conductions of bulk charges through the center neutral region as well as of accumulation charges through the surface accumulation region, and thus it includes all current conduction mechanisms of the NWFET operating under various bias conditions. Our model also includes surface depletion effects and series resistance effects. The NWFET model is implemented to the circuit simulator ADS, and the intrinsic part of the NWFET is developed by utilizing the symbolically defined device which is an equation-based nonlinear model. The results simulated from the newly developed NWFET model reproduce two types of the reported experimental results within a 10% error.

A double-layer current conduction model for high- κ gate dielectric materials with interfacial oxide or silicate layer

The current–voltage ( I– V) characteristics of metal-oxide-semiconductor (MOS) structures with hafnium oxide as the gate dielectric film were studied. Sharp shifts from a low-voltage ohmic regime to a tunneling conduction were observed in the high-voltage range. The paper demonstrates that this behavior can be described very well with a double-layer dielectric model. Excellent fittings of the experimental curves were obtained and the related key structural and physical parameters were obtained. The model fitting further suggests the optimal annealing conditions for preparing the hafnium oxide films.

Modeling of Current Conduction in HfO2 Stack Structures

not Available.

Normal-state properties of uniaxially pressed Bi1.65Pb0.35Sr2Ca2Cu3O10+delta ceramics

We have studied the effects of the uniaxial compacting pressure on the physical properties of polycrystalline Bi1.65Pb0.35Sr2Ca2Cu3O10+d (Bi-2223) superconductors. Powders of this material were pressed at different uniaxial compacting pressures ranging from ~ 90 to ~ 600 MPa and heat-treated at the same temperature. A characterization of samples by using Scanning Electron Microscopy and X-ray diffractometry indicated an appreciable improvement of the degree of texture with increasing pressure. The temperature dependence of the electrical resistivity r(T) exhibits a T-linear behavior at temperatures higher than T* ~ 235 K. The deviation of r(T) from the linear behavior below T* indicates the opening of the pseudogap, a feature confirmed by magnetic susceptibility measurements performed in powder samples. From linear fittings of the normal-state electrical resistivity we were able to separate contributions to r(T) arising from both the grain misalignment and microstructural defects. The results suggest that the grain orientation and the connectivity between them are improved with increasing compacting pressure. Also, based on the linearity of the electrical resistivity data both the transport electron-phonon coupling constant, ltr, and the mean free path, l, were estimated. We have found that in the sample with the highest degree of textureltr ~ 0.53, a value comparable with the one obtained in Bi-2223 single crystals. However, the result for l ~ 12.7 A at 300 K, in the same ceramic sample, is close to 3 times lower than the single crystal value. The influence of the intergranular electrical resistivity in determining band-theory parameters was analyzed within the framework of a current conduction model for granular superconducting materials.

Numerical model for current conduction in single layer organic light-emitting devices including both bulk and injection effects

A numerical model for current conduction in single layer OLEDs including both injection and bulk effects is proposed. Based upon this model, the dependences of current on the barrier height, device thickness and operation voltage, as well as the field distribution, are numerically investigated. It is found that the barrier height at the injection electrode limits the current conduction much more than the thickness of the organic layer, and, except near the electrodes, the electric field is nearly linearly distributed versus the distance from the injection electrode in the organic bulk, and the slope of the distribution decreases as the barrier height increases.

A closed-form expression to analyze electronic properties in delta-doped heterostructures

We develop a closed-form model to describe the electronic properties for delta modulation doped heterostructures, particularly the 2DEG sheet charge density and the electric field distribution in the direction of growth. The model includes the effects of real-space charge transfer and carrier degeneracy. The electron transfer and quasi-equilibrium condition in growth direction have been used in order to express the 2DEG sheet charge density that is only a function of material parameters and constants. An empirical constant, corresponding to quantized energy states, has been employed to further simplify this description and to arrive at a closed-form expression. Results from the analytical expressions are shown to agree well with numerical simulations based on a self-consistent solution of a modified Schrödinger and Poisson equations. In addition to their use in modeling of current conduction in modulation doped field effect transistors (MODFETs), we expect that these expressions would serve as versatile tools in the modeling of optical and spectral effects that occur in the AlGaAs/GaAs heterostructures.

Field distribution and criterion for bulk-limited and injection-limited current conduction in single layer organic light-emitting devices

A numerical model for current conduction in single layer OLEDs including both injection and bulk effect is proposed. Based upon this model, a nearly linear distribution of the electric field was found, and the slope of the distribution, or the field at the injection electrode (F0) is dependent on the energy barrier, mobility, trap density and trap depth. F0 equals the half of the mean field of the device (Fm), which equals the quotient of the bias to the thickness of organic layer, is proposed as the limit for bulk-limited (BL) and injection-limited (IL) conduction. OLEDs with F0 greater than Fm/2 are considered as IL-conducting, while those with F0 less than Fm/2 are considered as BL-conducting. It was found that, the state of current conduction is not only determined by the energy barrier at the injection electrode, but also by the mobility, trap density and trap depth of the organic semiconductor. OLEDs with high injection barrier (>0.7 eV), trap density less than 1019 cm-3, and reduced trap depth shallower than 5, will be IL-conducting, while those with low energy barrier (<0.2 eV), low carrier mobility (<10-6 cm2 V-1 s-1), and trap density higher than 1017 cm-3, will be BL-conducting.

Closed-form breakdown voltage model for PD SOI NMOS devices considering impact ionization of both parasitic BJT and surface MOS channel simultaneously

This paper reports a compact breakdown voltage model for partially depleted (PD) silicon-on-insulator (SOI) n-metal-oxide-semiconductor (NMOS) devices considering BJT/MOS impact ionization. Via the improved current conduction model considering BJT/MOS impact ionization this compact model provides an accurate prediction of the breakdown behavior of the PD SOI NMOS devices as verified by the experimental data and the MEDICI results. Based on the analytical model, when the gate voltage is lowered, the breakdown voltage decreases due to a stronger function of the parasitic BJT. In the subthreshold region, the breakdown voltage increases at a decreased gate voltage due to a weaker function of the parasitic BJT.

Effects of high current conduction in sub-micron Ti-silicided films

Modeling and characterization of high current conduction in sub-micron titanium disilicide (TiSi 2) films formed on n +/p + silicon and n +/p + polysilicon over active or field oxide under DC stress are reported. High current conduction in TiSi 2 films is shown to be strongly affected by the fabrication technology and process conditions. A model has been developed to explain the self-heating effect of silicide films under high DC stress. A parameter B is used to describe the sensitivity of the films to high current conduction. We found that the parameter B is linearly related to the initial resistance of the film, the temperature coefficient of resistance of TiSi 2 and the thermal impedance of the surrounding structures, and the results agree well with the experimental data.

Analysis of current conduction in short-channel accumulation-mode SOI PMOS devices

This paper reports a compact analytical current conduction model for short-channel accumulation-mode SOI PMOS devices. Based on the study, the current conduction mechanism in a short-channel accumulation-mode SOI PMOS device is different from that in a long-channel one. As verified by the experimental data, the compact analytical model considering channel length modulation and prepinchoff velocity saturation gives an accurate prediction of the drain current characteristics.

Thermoelectric power and anisotropic magnetoresistance of Fe-TM-B amorphous alloys

Thermoelectric power (TEP) between 4.2 and 700 K and anisotropic magnetoresistance (AMR) measurements are presented at 4.2 K and up to 8 T magnetic field on Fe80TM3B17 amorphous alloys where TM stands for transition metals. The early transition metals decrease both the absolute TEP and the AMR, while the late transition metals do not change them. The results could be qualitatively explained by the Kasuya theory and the two current conduction (TCC) model.

An investigation of the resistivity anisotropy in nickel alloys

The electrical resistivity of nickel alloys, if extrapolated to B=0, depends on the angle between the current and the magnetization. The authors have measured, at 4.2K, this resistivity anisotropy for ternary alloys of general composition Ni97A3-xBx, where A and B denote different metallic elements. These alloys include Ni(AlCr), Ni(AuCo), Ni(AuRh), Ni(CoRh), Ni(CoRu), Ni(CrFe), Ni(CrMn), Ni(CrSn), Ni(CrTi), Ni(CuRh), Ni(CuRu), Ni(CuV), Ni(FePt), Ni(FeRe), Ni(RhRu) and Ni(RuTi). The experimental results have been analyzed in terms of Mott's two current conduction model. In this model it is assumed that the conduction electrons of spin direction parallel or antiparallel to the magnetization contribute individually to the current. Each impurity element in nickel has got two residual resistivities, one for each spin current. These residual resistivities are derived for the ferromagnetic moment parallel and perpendicular to the current. It is found that the resistivity anisotropy is large for one of the spin currents (about +10%) while that for the other varies around -2%.

Zero temperature spin mixing in nickel

Measurements of the transport properties of ni-based alloys show deviations from the expectations of a two current conduction model when the impurity concentration is low. The deviations can be accounted for by introducing a zero temperature spin-mixing rate.

A quantitative investigation of the two current conduction in nickel alloys

The electrical resistivity at 4.2K has been measured for ternary alloys based on nickel (Ni97AxB3-x, where A and B denote metallic elements). These include Ni(AlCr), Ni(AuCo), Ni(AuRh), Ni(CoRh), Ni(CoRu), Ni(CrFe), Ni(CrMn), Ni(CrSn), Ni(CrTi), Ni(CuRh), Ni(CuRu), Ni(CuV), Ni(FePt), Ni(FeRe), Ni(RhRu) and Ni(RuTi). Large deviations from Matthiessen's rule i.e. the additivity of individual residual resistivities, are found to be a general phenomenon. The experimental results have been analysed in terms of Mott's two current conduction model; quantitative values for the spin sub-band resistivities are derived for each of the solute elements mentioned above. For a given solute metal these values are fairly independent of the set of ternary alloys from which they are determined, which presents a strong argument in favour of the applicability of the two current conduction model to nickel alloys.

Growth and Characterization of Polycrystalline Silicon

Polycrystalline silicon is deposited by pyrolysis of silane in an rf heated epitaxial reactor. The grains exhibit a fibrous microstructure having an 〈110〉 preferred orientation in the growth direction. Growth is inhibited in the presence of excess arsine and accelerated in the presence of diborane. The results are explained in terms of catalysis and poisoning of surface adsorption sites responsible for reaction. A simple model for current conduction in polycrystalline silicon is described based on grain size, grain doping, and effective barrier height due to the grain boundary. This model satisfactorily explains the observed temperature dependence of the resistivity of undoped films and also the large values of resistivity which are observed for dopant concentrations .

Field Modulation of Liquid Induced Excess Surface Currents on Germanium p-n Junctions

The field modulation of liquid induced surface currents on germanium surfaces has been investigated. The field induced current is shown to conform to the behavior seen by liquid induced currents on germanium surfaces. The modulation increases with decreasing temperature down to the melting point of the liquid and then decreases radically to nearly zero. The modulation effect is seen only when polar liquid ambients are used. A qualitative explanation of the effect is discussed in terms of a model for current conduction in which the charge carriers move in the liquid outside of the semiconductor. The increased current with external field is thought to arise from the orientation of the dipoles in the liquid giving increased mobility to the charge carriers.