Investigation of the current-voltage characteristics of thin-film ZnSe-ZnTe heterojunction structures

This paper investigates the current-voltage characteristics of thin-film ZnSe-ZnTe heterojunction structures grown on zinc substrates. It is shown that the maximum rectification coefficient for such systems is observed when the condition d_1,2=d₀ is satisfied. On the basis of the general equation of the current-voltage characteristics of heterojunctions taking into account the boundary conditions, equations are derived which describe the behavior of the forward and back branches of the current-voltage characteristic of the heterojunction under consideration, and an explanation is given of the divergence between the theoretical and experimental results.     

Double resonance in the system of coupled Josephson junctions

The effect of LC shunting on the phase dynamics of coupled Josephson junctions has been examined. It has been shown that additional (rc) branches appear in the current-voltage characteristics of the junctions when the Josephson frequency ω_J is equal to the natural frequency of the formed resonance circuit ω_rc. The effect of the parameters of the system on its characteristics has been studied. Double resonance has been revealed in the system at ω_J = ω_rc = 2ω_LPW, where ω_LPW is the frequency of a longitudinal plasma wave appearing under the parametric-resonance conditions. In this case, electric charge appears in superconducting layers in the interval of the bias current corresponding to the rc branch. The charge magnitude is determined by the accuracy with which the double resonance condition is satisfied. The possibility of the experimental implementation of the effects under study has been estimated.     

Current layers and filaments in a semiconductor model with an impact ionization induced instability

Dissipative structures associated with an instability in a semiconductor far from equilibrium are studied. A generation-recombination mechanism, which effects anS-shaped current-voltage characteristics, is coupled to diffusion and drift of the electrons. The spectrum of linear recombination-diffusion modes is computed for the homogeneous steady state with negative differential conductivity. The obtained soft mode instability gives rise to the bifurcation of a family of transversally modulated inhomogeneous steady states and longitudinal travelling waves. The inhomogeneous steady states are calculated from the full nonlinear transport equations for plane and cylindrical geometries. They correspond to oscillatory and solitary concentration profiles, including depletion and accumulation layers and cylindrical filaments. Conditions for the formation of kink-shaped coexistence profiles are established in terms of equal area rules. The current-voltage characteristics are extended to include inhomogeneous current states. Nonequilibrium phase transitions between various branches of these characteristics are associated with switching through filamentation.     

Single Cooper pair pump

We have operated a Cooper pair pump, a linear array of superconducting tunnel junctions in which single Cooper pairs are moved under the influence of ac signals applied to two gate electrodes. The pump is based on the Coulomb blockade of charge tunneling. Because of the small junction capacitance precisely one Cooper pair is transferred per ac cycle. The current-voltage characteristics of this device show current plateaus close to 2ef, wheref is the frequency of the ac voltages. Deviations are explained in terms of Zener tunneling, Cooper pair co-tunneling, and sporadic quasiparticle tunneling.     

Microwave noise of a thin-film YBa2Cu3O7−x bridge in the resistive state

The effective input noise temperature T _e of a bridge made from a highly oriented YBaCuO film is measured at a frequency of 4.6 GHz. The bridge is brought to a weakly resistive state by a dc current, by microwave radiation at a frequency of 9.4 GHz, or by a combination of the two. Along with the noise temperature, the current-voltage characteristics and impedance of the bridge are also measured at a frequency of 4.6 GHz. At T=78 K the value of T _e does not exceed 120 K. Analysis of the results allows one to compare the experimental values of T _e with the values determined by the equilibrium Nyquist noise of overheated normal domains and indicates the presence of excess noise at a level comparable to the Nyquist noise. Zh. Tekh. Fiz. 67, 89–93 (February 1997)     

Electrical properties of metal-vanadium-borate glass-gallium arsenide structures

The results of a study of the electrical properties of MIS structures based on n-type GaAs are presented. The static current-voltage characteristics and the dependences of the capacitance and active conductance on the voltage on the MIS structure in the frequency range of the test signal from 22 to 10⁵ Hz at room temperature and in the temperature range 295–367 K at a frequency of 10³ Hz are analyzed in detail. A method is proposed for determining the total density of surface states N_ts, which determine the position of the Fermi energy on the semiconductor surface for MIS structures with large N_ts.V. D. Kuznetsov Siberian Physicotechnical Institute at Tomsk State University. Translated from Izvestiya Vysshykh Uchebnykh Zavedenii, Fizika, No. 11, pp. 99–108, November, 1992.     

Field electron emission form single-walled carbon nanotubes with deposited cesium atoms

It has been found that deposition g of cesium atoms on single-walled carbon nanotubes covered with potassium atoms not only drastically increases emission current but also considerably changes the shape of current-voltage characteristics of field electron emission, namely, the characteristics become nonlinear in Fowler-Nordheim coordinates. It has been assumed that this effect is associated with the fact that field electron emission in these layers comes from single-walled carbon nanotubes, which have p-type conductivity after potassium treatment, while deposition of cesium leads to the formation of p-n junctions near nanotube tips. Part of the applied voltage drops in p-n junction, thus causing a nonlinearity of current-voltage characteristics.     

Mechanism of charge transfer in n-CdS/p-CdTe heterostructures with a thick layer of the CdTe1 ? xSx solid solution

The current-voltage and capacitance-voltage characteristics of the n-CdS/p-CdTe heterosystem are investigated. An analysis of the results obtained has demonstrated that a high-resistance i layer (the CdTe_{1 − x} S _x solid solution), which is inhomogeneous not only in the electrical conductivity but also in the composition, is formed at the n-CdS/p-CdTe heterointerface. The thicknesses of the solid-solution layers are estimated from the capacitance-voltage characteristics, and regions with different types of conduction are found to exist in the intermediate layer. It is shown that the ambipolar diffusion and drift in the high-resistance CdTe_{1 − x} S _x solid-solution layers are directed toward each other, thus resulting in the appearance of a sublinear portion in the current-voltage characteristics described by the dependence V = exp(Iaw). The observation of a sublinear portion in the current-voltage characteristics measured in both the forward and reverse electric current directions over a wide temperature range 77–323 K suggests that the diffusion-drift regime can occur in different parts of the i layer, depending on the electric current density and the ambient temperature. The changes observed in the electric current and capacitance, as well as in the current-voltage and capacitance-voltage characteristics, after ultrasonic irradiation indicate that, in the CdTe_{1 − x} S _x solid solutions, there exist metastable states, which most probably decay under ultrasonic irradiation and then again form solid solutions with more stable states. Original Russian Text ? Kh.Kh. Ismoilov, A.M. Abdugafurov, Sh.A. Mirsagatov, A.Yu. Leĭderman, 2008, published in Fizika Tverdogo Tela, 2008, Vol. 50, No. 11, pp. 1953–1957.     

On the mechanism of dissipation in the internal Josephson effect in layered superconductors at low temperatures

The current-voltage characteristics (IVCs) of a layered superconductor with singlet d pairing at low temperatures are calculated in the internal Josephson effect (IJE) regime. Coherent electron tunneling between layers is assumed. A finite resistance of the superconductor in the resistive state arises because of quasiparticle transitions through the superconducting gap near nodes. Because of charge effects the interaction of the Josephson junctions formed by the layers does not lead to substantial differences in the shapes of different branches of the IVCs. The model describes the basic qualitative features of the effect in high-temperature superconductors for voltages which are low compared with the amplitude of the superconducting gap. Pis’ma Zh. éksp. Teor. Fiz. 70, No. 8, 516–521 (25 October 1999)     

Discrete tunneling of holes in porous silicon

It is pointed out that in the partial oxidation of porous silicon (PS) formed on heavily doped crystals, the topology of the pores can result in the formation of an anisotropic material with strings of nanometersized silicon granules embedded in insulating silicon dioxide SiO₂. In this range of granule sizes the correlation effects in the tunneling of electrons (holes) are strong on account of their Coulomb interaction. This should be manifested as discrete electron and hole tunneling at temperatures comparable to room temperature. The room-temperature current-voltage characteristics of n ⁺-PSp ⁺-p ⁺ diode structures with a PS interlayer on p ⁺-Si, which exhibit current steps on the forward and reverse branches, are presented. The current steps are attributed to discrete hole tunneling along the silicon strings in SiO₂. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 10, 794–797 (25 May 1998)     

Current-voltage characteristics of a spin half-metallic transistor

A new design of spin transistor based on half-metallic ferromagnets (referred to as a spin half-metallic transistor) is suggested, and its current-voltage characteristics are studied theoretically. Like a bipolar transistor, the new device can amplify current. At the same time, the properties of a spin half-metallic transistor depend considerably on the mutual orientation of the magnetizations of its three contacts. We also propose a device based on an F ^↑-F ^↓ junction. This device consists of two single-domain half-metallic parts with opposite magnetizations. There is a range of voltages where the current-voltage characteristics of an F ^↑-F ^↓ junction and a semiconductor diode are similar. The behavior of an F ^↑-F ^↓ junction under different conditions is studied.     

Coherent transport in disordered metals out of equilibrium

We derive a formula for the quantum corrections to the electrical current for a metal out of equilibrium. In the limit of linear current-voltage characteristics our formula reproduces the well known Altshuler-Aronov correction to the conductivity of a disordered metal. The current formula is obtained by a direct diagrammatic approach, and is shown to agree with what is obtained within the Keldysh formulation of the non-linear sigma model. As an application we calculate the current of a mesoscopic wire. We find a current-voltage characteristics that scales with eV/kT, and calculate the different scaling curves for a wire in the hot-electron regime and in the regime of full non-equilibrium. Received 13 June 2001     

Features of the conductivity of the quasi-one-dimensional compound TiS3

The structure and transport properties of single crystal whiskers of the TiS₃ quasi-one-dimensional semiconductor have been investigated. The anisotropy of the conductivity in the plane of layers (ab) has been measured as a function of the temperature. The anisotropy at 300 K is 5 and increases with a decrease in the temperature. Features on the temperature dependences of the conductivity along and across the chains are observed at 59 and 17 K. Near the same temperatures the form of the current-voltage characteristics measured along the chains is qualitatively changed. The current-voltage characteristics below 60 K exhibit nonlinearity and have a threshold form below 10 K. The results indicate possible phase transitions and the collective conduction mechanism at low temperatures.     

Design and Analysis of InGaN-GaN Modulation-Doped Field-Effect Transistors (MODFETs) for 90 GHz Operations

A Modulation-Doped Field-Effect Transistor (MODFET) structure having quantum wire channel realized in InGaN-GaN material system is presented. This paper presents design and analysis of a novel one-dimensional Modulation-Doped Field-Effect transistor (1D MODFET) in InGaN-GaN material system for microwave and millimeter wave applications. An analytical model predicting the transport characteristics of the proposed MODFET device is also presented. Analytical results of the current-voltage and transconductance characteristics are presented. The unity-current gain cutoff frequency (f _T) of the proposed device is computed as a function of the gate voltage V _G. The results are compared with two-dimensional GaN/AlGaN MODFET and HFET devices. The analytical model also predicts that 0.25 m channel length devices will extend the use of InGaN-GaN MODFETs to above 90GHz.     

Surface plasmon polaritons of symmetric and asymmetric metamaterial slabs

The p and s-polarized surface plasmon polaritons (SPPs) of symmetric and asymmetric slabs formed arbitrarily by four types of conventional materials: dielectrics, negative dielectric permittivity materials, negative magnetic permeability materials, and left-handed materials are comprehensively analysed. The existence regions, dispersion relations, and excitation of SPPs in different frequency regions are investigated in detail. For symmetric slabs, the numbers and the frequency positions of surface polariton branches are quite different. At the same time, the pairs of the p or s-polarized SPP branches occur in the same frequency range. For asymmetric slabs, the SPP branches in mid- and high-frequency ranges are greatly different. In addition, the slab thickness has a great effect on SPPs of asymmetric and symmetric slabs. The attenuated total reflection spectra for the cases of p and s polarizations in these slabs are also calculated.     

Electrical characteristics of a metal–insulator–semiconductor memory structure containing Ge nanocrystals

A metal–insulator–semiconductor structure device with Ge nanocrystals in SiO₂ was synthesized and the electrical characteristics were investigated. Capacitance–voltage (C–V) curves show hysteresis and the measurements indicate that the device has charge storage effects and stores more holes than electrons. For decreasing measurement frequencies from 1 MHz to 500 Hz, both branches of the C–V hysteresis shift in the positive voltage direction. The slope of the left flank of the C–V hysteresis curve becomes stretched out with decreasing frequency. The slope of the right one appears frequency independent, while there is a small hump/step on the right flank of the C–V hysteresis curve for the lower frequency cases (500 Hz and 1 kHz). The role of Si/SiO₂ interface states is discussed.     

A theory for the α2F-dependence of the electrical impedance of a point contact between metals

The current-voltage characteristic of a metal-metal point contact has been calculated via a solution of the semi-classical Boltzmann transport equation. Electron-phonon interaction is contained in this procedure. The point contact current-voltage characteristic appears to be mainly due to processes involving the spontaneous creation of a single phonon. The resulting signal is proportional with α²F, but it also depends on the tunneling probability T of the contact. Double-phonon creation processes, and electron-hole pair production ones are considered as contributions to the background signal.     

CdTe/CdS太阳电池I-V，C-V特性研究

测量了CdTe太阳电池器件从50kHz至1MHz频率范围的电容-电压特性，计算了吸收层的载流子浓度和空间电荷区的位置，电容-电压特性测试结果出现两个峰，峰特征与测试频率有关，用多结模型进行模拟分析，解释了实验结果.测量了电池从220K至300K的变温暗电流-电压特性，得出电池的反向暗饱和电流密度J₀和二级管理想因子A，分析了J₀，A随测量温度的变化,并讨论了电池器件的电流特性. 关键词： CdTe太阳电池 电流-电压特性 电容-电压特性     

直流电致发光(DCEL)器件在交流(AC)电压下的I-V,B-V和B-I特性

本文研究了DCEL器件在AC条件下的电流-电压(I-V),亮度-电压(B-V)和亮度-电流(B-I)特性.提出了在不同激发条件下的I-V,B-V和B-I的经验公式.证明了DCEL器件在AC条件下按激发条件可分为三个负载区:容性负载区,电阻负载区和混合负载区.在不同的负载区DCEL器件呈现完全不同的光电特性.证明了在不同负载区工作时磷光粉层内电场分布和电子能量分布截然不同.分析了上述特性的原因.证明了老化和形成过程具有同样的物理机制,老化是形成过程的继续.     

Characteristic features of vortex depinning in a layered superconductor

The field H*(T) for the onset of dissipation is estimated self-consistently from the results of an investigation of the transverse resistance and current-voltage characteristics of a Bi₂Sr₂CaCu₂O₈ (BSCCO-2212) single crystal in a mixed state. It is established that H* is close to H _c1 in the interval T _c/2⩽T⩽T _c. Rapid growth of H*(T), accompanied by a transformation of the current-voltage characteristics, as the temperature decreases below ≈ 40 K attests to the formation of a nonvanishing region of stability of an ordered state of the vortex system, possibly as a result of a change in the effective dimensionality of the fluxoid. Pis’ma Zh. éksp. Teor. Fiz. 65, No. 8, 629–634 (25 April 1997)