The mobility of charge carriers in a size-quantized coated semiconductor wire

Within the framework of a staircase infinitely deep potential well model, the mobility of charge carriers is calculated for scattering on impurity centers located on the axis of a size-quantized semiconducting coated wire. Calculations are done for the dielectric constant mismatch of the wire, coating and surrounding environment, taking into account the difference of the effective masses in the wire and coating. The effect of a longitudinal magnetic field on mobility is also considered. Numerical results are presented for the GaAs–Ga_1−xAl_xAs system at different values of the wire and coating radii, the alloy concentration x, and magnetic field.     

Effect of surface scattering of charge carriers on the high-frequency conductivity of a thin cylindrical semiconductor wire

The problem of high-frequency conductivity of a thin cylindrical semiconductor wire has been solved by the kinetic method. The diffuse-specular mechanism of reflection of charge carriers from the inner surface of the wire has been considered. Calculations have been performed for an n-type (p-type) nondegenerate semiconductor with a standard spherically symmetric energy band. The ratio between the cross-section radius of the wire and the mean free path of charge carriers is assumed to be arbitrary.     

Effect of transverse entrainment of charge carriers by the field of two electromagnetic waves in a semiconductor

The effect of transverse entrainment of charge carriers by two electromagnetic waves propagating in mutually perpendicular directions in a semiconductor with a parabolic dispersion law has been investigated. The dc component of the electric current density that appears in the direction perpendicular to the wave vectors has been calculated in the constant relaxation time approximation. It has been shown that the transverse dc current vanishes at a particular phase difference of the incident waves determined by the relaxation time of charge carriers in the material.     

Kinetics of the surface charging of a semiconductor during adsorption

The kinetic characteristics of the surface charging of a semiconductor during adsorption are analyzed, due allowance being made for the recharging of the biographic surface states during the adsorption process. It is shown that the form of the kinetic curves depends very substantially on the relationship between the characteristic relaxation times of the adsorption and biographic surface states.     

Effect of excessive pressure on the drift mobility of charge carriers in poly(diphenylene phthalide) films

The electron-hole transport in poly(diphenylene phthalide) films has been investigated. The dependence of the drift mobility of charge carriers on the excessive mechanical pressure has been studied using the time-of-flight method. It has been revealed that, with an increase in the thickness of the polymer film, the dispersive transport of charge carries gives way to the quasi-dispersive transport. In thin films in the prethreshold range (i.e., before switching of the samples to the highly conductive state under excessive pressure), the electron mobility increases and exceeds the hole mobility. The experimental results have been discussed in the framework of the model describing the transport through the channels formed by metastable electron-hole pairs.     

Photoconductivity of a semiconductor with a transverse gradient of drift velocity of charge carriers

The spectral photosensitivity of a semiconductor with a gradient of the drift velocity of charge carriers has been investigated. It was found to be of either selective or bolometric type depending on mutual directions of incident light and of the gradient. Photoconductivity of germanium samples of ringlike geometry was studied experimentally over the spectral range 0.8–2.2 μm at room temperature. The main results are: decay of the photocurrent in a semiconductor where the gradient differs from the exponential one and depends on the mutual directions of the gradient and diffusion of carriers; the amplitude of the photocurrent depends not only on the typical parameters but on light direction and also gradient; determination of both effective lifetime of carriers and the bandgap by the Moss method is not valid for a semiconductor with a gradient of drift velocity; a photodetector with parameters reversibly controlled by an electric field is possible.     

Influence of oxygen adsorption on the surface potential of a metal oxide semiconductor

Analytical expressions describing dependences of the surface density of adsorbed oxygen ions and energy band bending in the subsurface region of a metal oxide semiconductor on the oxygen concentration that consider not only the process of neutral gas particle adsorption, but also their charge transfer at the expense of electron capture from the conduction band are presented. It is demonstrated that the heat of oxygen ion absorption is equal to the sum of the heat of neutral particle adsorption and the energy gap between the Fermi level and the level of the oxygen ion on the semiconductor surface. When the adsorption equilibrium is established, an analytical expression describing the time dependence of the energy band bending can be obtained only for small change of the oxygen concentration in the gas mixture.     

Effect of an external resonator on the space charge dynamics in a semiconductor superlattice

The dynamics of a semiconductor superlattice in an external resonator is studied. It is shown that the external electrodynamic system considerably complicates the behavior of the superlattice by exciting random oscillations and leads to additional negative differential conductivity in the I–V characteristic that is not observed in an autonomous system.     

Effect of a charge layer on the plasmon-polariton dispersion curve in doped semiconductor superlattices

We consider the effects of a charge layer (accumulation and depletion layers) on the spectrum of collective plasmon-polariton modes of a semiconductor superlattice consisting of alternating mediaA andB, where mediumA is an-doped semiconductor and mediumB an insulator. The effect of the charge layer is taken into account assuming a linear position dependence for the free-carrier concentration and for the dielectric function, within mediumA. Applications are made considering mediumA asn-type semiconductor and mediumB being vacuum. We compare our results with those obtained in the abscence of the charge layer and we discuss their differences.     

Monitoring surface charge movement in single elongated semiconductor nanocrystals

We demonstrate a universal correlation between the spectral linewidth and position of the excitonic transition in the spectral jitter observed from single elongated colloidal quantum dots. Breaking the symmetry of electron and hole confinement as well as of the spatial directions for surface charge diffusion enables us to microscopically track meandering surface charges, providing a novel probe of the particle's nanoenvironment. Spectral diffusion exhibits only a weak temperature dependence, which allows us to uncover the single particle homogeneous linewidth of 50 meV at room temperature.     

On the possibilities of implementing a stochastic model for the distribution of nonequilibrium minority charge carriers in a semiconductor material

Some possibilities of implementing a procedure for estimating statistical characteristics (expectation and autocorrelation function) of the distribution of minority charge carriers (MCCs) generated in a homogeneous semiconductor material are studied. The developed procedure is based on the projection method and the matrix operator technique. It is assumed that the electrophysical parameters of the material (lifetime, diffusion coefficient, and surface recombination rate of MCCs) are random quantities (variables) and obey the Gaussian distribution law. The effect of the variance of these quantities on the depth distribution of MCCs is considered. Some possibilities of this method are illustrated for the case of MCC excitation by a broad beam of electrons with moderate energies.     

Interaction between free carriers and optical field along the surface of a semiconductor material

We report an experiment showing dynamically the interaction of free carriers with an infrared wave (λ = 10.6μ) guided by the free-carrier effect (static interaction) along the surface of a semiconductor crystal (GaAs). Finally, we present as theoretical model of this experiment.     

The mobility of charge carriers in molecularly doped polymer films with various thicknesses

The dependence of the mobility of charge carriers in molecularly doped polycarbonate on the thickness of the polymer was studied at two dopant DEH concentrations (30 and 50 wt %). The mobility of holes in the more concentrated polymer did decrease as the film thickness increased in close agreement with the predictions of the theory of weakly nonequilibrium transport with a dispersion parameter of 0.75. For films with a lower dopant concentration, such a categorical statement cannot be made, because mobility can either decrease as the film thickness increases or remain almost unchanged depending on the method for data processing. For this reason, it is not recommended to use the dependence of the time of flight on film thickness as a criterion for selecting the mechanism of the transport of charge carriers in molecularly doped polymers.     

Contact electrohydrodynamic waves of free charge carriers at the interface of two semiconductor layers

It is shown that electrohydrodynamic waves similar to gravity waves at the interface of two liquids can propagate in a semiconductor structure composed of two semiconductor layers with different charge carrier densities and placed in a transverse electric field. The conditions for existence of such waves are specified. The linear and nonlinear modes of wave propagation are studied. State Technical University, Ulianovsk, Russia, Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40, No. 9, pp. 1164–11171, September, 1997.     

Drift mobility and kinetics of transport of excess charge carriers in glassy CdGexAs2

Conclusions We tried to measure transient conductivity response to pulse strongly absorbed excitation (light, accelerated electrons) in sandwich type samples of glassy CdGe _x As₂ compounds. We observed the signal due to transport of free excess carriers. From analysis of experimental results we conclude that in our materials strong trapping effects are present, so the range of excited carriers is very short (10^–4-10^–3 cm) even in the highest electrical fields used (to 10⁴ V. cm^–1). Estimates of upper limit of drift mobility give the values 10^–1- 1 cm² V^–1 sec^–1. We did not succeed in determining the type of carriers which are responsible for the observed effects.     

Effects of corotron size and parameters on the dielectric substrate surface charge

Effects of variation of parameters of a corona device (corotron) used in electro-photographic machines on the amount of surface charge build-up on the surface of dielectric substrate were studied. Particular attention was given to the effect of corotron dimension including wire–shields and wire–plate distances, substrate thickness, shields insulation and the substrate speed on the amount of substrate surface charge. The computational analyses were performed for a two-dimensional cross-section of the corotron under steady-state condition. The Maxwell equations were solved and the electrical quantities in a rectangular positive single wire corotron were evaluated. The simulation results showed that for a fixed wire voltage, the corotron size, the substrate thickness, insulation of shields and the substrate speed will affect the distributions of electrical quantities in the corotron. The wire–substrate distance and the substrate speed, however, were found to be the main parameters that control the amount of surface charge build-up on the substrate.     

Rate of intersubband transitions of charge carriers in semiconductor quantum wells as a result of their Coulomb interaction

The intersubband scattering of charge carriers in semiconductor quantum wells as a result of their Coulomb interaction has been theoretically investigated. Analytical expressions for the rate of intersubband transitions in the process of electron—electron and electron—hole collisions have been derived in the Born approximation. The theoretical and experimental data on the photoluminescence decay time, obtained for the case of a nondegenerate distribution of charge carriers, were in qualitative agreement. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 6, pp. 782–787, November–December, 2005.     

Effect of drifting carriers on longitudinal electro-kinetic waves in ion-implanted semiconductor plasmas

We present an analytical study of wave spectra of electro-kinetic waves propagating through semiconductor plasma, whose main constituents are drifting electrons, holes and non-drifting negatively charged colloids. By employing the hydrodynamical model of multi-component plasma, a compact dispersion relation for the same is derived. This dispersion relation is used to study slow electro-kinetic wave phenomena and resultant instability numerically. We find some important modifications in the wave spectra of the slow electro-kinetic branch. It is found that the drift velocities of electrons and holes are responsible for converting two aperiodic modes into periodic ones. The applied dc electric field increases the phase velocities of contra-propagating modes. The amplification coefficients of propagating modes can be optimized by tuning the amplitude of applied electric field and wave number. It is hoped that the results of this investigation should be useful in understanding the wave spectra of slow electro-kinetic waves in ion-implanted semiconductor plasma subjected to a dc electric field along the direction of wave propagation.