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Yu. G. Gurevich

Publications and source records attributed to Yu. G. Gurevich.

16 recordsLinked to original sources
arXiv2016

Nonlinear charge transport in bipolar semiconductors due to electron heating

It is known that when strong electric field is applied to a semiconductor sample, the current voltage characteristic deviates from the linear response. In this letter, we propose a new point of view of nonlinearity in semiconductors which is associated with the electron temperature dependence on the recombination rate. The heating of the charge carriers breaks the balance between generation and recombination, giving rise to nonequilibrium charge carriers concentration and nonlinearity.

cond-mat.mtrl-sci↗
arXiv2004

Recombination and Lifetimes of Charge Carriers in Semiconductors

In this Communication, it is shown that models used for describing generation and recombination of electrons and holes lead to disagreements with Maxwell's electrodynamics. Self-consistent expressions, more adequately depicting the actual physical processes of electron-hole recombination in semiconductors are obtained. It is shown that the electron and hole lifetimes can be defined correctly only for the special cases when the electron and hole nonequilibrium concentrations are the same, these lifetimes being equal. The influence of temperature inhomogeneity on the recombination is also considered. The recombination rate for hot electrons is obtained in the case when the electron and hole temperatures differ.

cond-mat.soft↗
arXiv2002

Electron and Phonon Temperature Relaxation in Semiconductors Excited by Thermal Pulse

Electron and phonon transient temperatures are analyzed in the case of nondegenerate semiconductors. An analytical solution is obtained for rectangular laser pulse absorption. It is shown that thermal diffusion is the main energy relaxation mechanism in the phonon subsystem. The mechanism depends on the correlation between the sample length and the electron cooling length in an electron subsystem. Energy relaxation occurs by means of the electron thermal diffusion in thin samples (), and by means of the electron-phonon energy interaction in thick samples (). Characteristic relaxation times are obtained for all the cases, and analysis of these times is made. Electron and phonon temperature distributions in short and long samples are qualitatively and quantitatively analyzed for different correlations between the laser pulse duration and characteristic times.

cond-mat↗
arXiv2002

"Resonance" phenomena in thermal diffusion processes in two-layer structures

The dependence on chopper frequency of the effective thermal diffusivity and effective thermal conductivity in photoacoustic experiments is discussed. The theoretical model of a two-layer structure at rear-surface illumination in the high frequency limit is considered. It is shown that the effective thermal diffusivity presents ``resonance'' while the effective thermal conductivity sharply changes its magnitude and sign. Such ``resonant'' behavior strongly depends on the surface thermal conductivities associated with the interface thermal contacts.

cond-mat↗
arXiv2002

The Role of Non-Equilibrium Carriers in Formation of Thermo-E.M.F. in Bipolar Semiconductors

A new approach to thermoelectric phenomena, as a linear transport process of non-equilibrium charge carriers, is presented. The role of non-equilibrium carriers, as well as surface and bulk recombination, is demonstrated to be crucial even within a linear approximation. Electron and hole Fermi quasi-levels appeared in a thermal field are calculated in the case of thermoelectric current flow through a circuit. It is shown, for the first time, that the Fermi quasi-level of one of subsystem of quasi-particles can be a non-monotonic function of the coordinates. General expressions for the thermoelectric current, thermo-e.m.f., and electrical resistance of bipolar semiconductors have been obtained. For the first time the surface recombination and surface resistance were taken into account.

cond-mat↗
arXiv2002

New physical principles of contact thermoelectric cooling

We suggest a new approach to the theory of the contact thermoelectric cooling (Peltier effect). The metal-metal, metal-n-type semiconductor, metal-p-type semiconductor, p-n junction contacts are analyzed. Both degenerate and non-degenerate electron and hole gases are considered. The role of recombination in the contact cooling effect is discussed by the first time.

cond-mat↗
arXiv2002

About one forgotten mechanism of nonlinearity in the theory of hot electrons

It is shown that in general electron gas heating inevitably results in the change of the carrier concentration in the conduction band. It is proved, that this change, as a rule, leads to the kinetic coefficient nonlinearity of the same order, as the change of mobility does. The conditions are determined, when this change can be neglected.

cond-mat↗
arXiv2002

Boundary Conditions in an Electric Current Contact

In most electronic devices, electric current of both types (electrons and holes) flows through a junction. Usually the boundary conditions have been formulated exclusively for open circuit. The boundary conditions proposed here bypass this limitation by the first time, as far as we are aware. Besides, these new boundary conditions correctly describe current flow in a circuit, i.e., closed circuit conditions, which are the usual operation conditions for electronic devices and for the measurement of many transport properties. We also have generalized the case (as much as it is possible in a classical treatment), so self-consistent boundary conditions to describe current-flow through a contact between two arbitrary conducting media are developed in the present work. These boundary conditions take into account a recently developed theory: influence of temperature space inhomogeneity due to the interfaces and quasi-particles temperature-mismatch on thermo-generation and recombination. They also take into account surface resistance, surface recombination rates and possible temperature discontinuities at the interface due to finite surface thermo-conductivity. The temperature difference between current-carriers and phonon subsystems is also included in this approach.

cond-mat.mtrl-sci↗
arXiv1997

Spatially nonuniform energy distribution of electrons in a submicron semiconductor film

The symmetric part of the distribution of the electrons in a semiconductor submicron film, placed between a heater and refrigeration unit, is derived and analyzed. It is shown that, in general, it is of non-Fermi (non-Maxwellian) nature. A new mechanism is proposed to account for the non-Maxwellian form of the symmetric part of the distribution function. This mechanism is based on the different energy dependences of the momentum relaxation time in the bulk of the semiconductor and its skin layer.

cond-mat↗
arXiv1997

Theory of thermoelectric effects when the temperature approximation is incorrect

The flow of a thermoelectric current through a semiconductor of submicron dimensions is analyzed. The rate of surface relaxation of the energy is assumed to be much higher than the rate of electron-electron collisions. Under these conditions, it is incorrect to describe the electron gas by means of a Maxwellian distribution and thus to describe the thermoelectric effects in terms of an electron temperature and a chemical potential. A theory is derived for these effects. This theory does not include the latter parameters and is based on a non-Maxwellian distribution which is spatially nonuniform in terms of energy.

cond-mat↗
arXiv1997

Problem of formation of an emf in a semiconductor and its transfer to an external circuit

A general description is given of a process of formation of an emf in a medium with nonequilibrium carriers. The appearance of anomalous emfs is predicted for several semiconductor structures. Such emfs appear as a result of photogeneration of the majority carriers or, for example, due to homogeneous heating of electrons and holes along the whole circuit. An analysis is made of the problem of determination of an emf inside a multicomponent medium and of recording it in an external circuit.

cond-mat↗
arXiv1996

Electron and Phonon Thermal Waves in Semiconductors: an Application to Photothermal Effects

The electron and phonon temperature distribution function are calculated in semiconductors. We solved the coupled one-dimensional heat-diffussion equations in the linear approximation in which the physical parameters on the sample are independent of the temperature. We also consider the heat flux at the surface of the semiconductor as a boundary condition for each electron and phonon systems instead of using a fixed temperature. From this, we obtain an expression for electron and phonon temperature respectively. The characterization of the thermal waves properties is duscussed and some practical procedures for this purpose provide us information about the electron and phonon thermal parameters.

cond-mat↗
arXiv1996

New Mechanism of Magnetoresistance in Bulk Semiconductors: Boundary Condition Effects

We consider the electronic transport in bounded semiconductors in the presence of an external magnetic field. Taking into account appropriate boundary conditions for the current density at the contacts, a change in the magnetoresistance of bulk semiconductors is found as compared with the usual theory of galvanomagnetic effects in boundless media. New mechanism in magnetoresistance connected with the boundary conditions arises. In particular, even when the relaxation time is independent of the electron energy, magnetoresistance is not vanish.

cond-mat↗
arXiv1995

Thermal Diffusion of a Two Layer System

In this paper thermal conductivity and thermal diffusivity of a two layer system is examined from the theoretical point of view. We use the one dimensional heat diffusion equation with the appropriate solution in each layer and boundary conditions at the interfaces to calculate the heat transport in this bounded system. We also consider the heat flux at the surface of the samle as boundary condition instead of using a fixed tempertaure. From this, we obtain an expression for the efective thermal diffusivity of the composite sample in terms of the thermal diffusivity of its constituent materials whithout any approximations.

cond-mat↗
arXiv1995

The Nature of Thermopower in Bipolar Semiconductors

The thermoemf in bipolar semiconductors is calculated. It is shown that it is necessary to take into account the nonequilibrium distribution of electron and hole concentrations (Fermi quasilevels of the electrons and holes). We find that electron and hole electric conductivities of contacts of semiconductor samples with connecting wires make a substantial contribution to thermoemf.

cond-mat↗