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. 72.20.PaTypeset using REVT E X

A new approach is suggested to explain the Peltier effect. It assumes that the Peltier effect is not an isothermal effect. The approach is based on the occurrences of induced thermal fluxes in a structure which consists of two conducting media, through which a dc electric current flows. These induced thermal diffusion fluxes arise to compensate for the change in the thermal flux caused by the electric current (the drift thermal flux) flowing through the junction, in accordance with the general Le Châtelier-Braun principle. The occurrence of these thermal diffusion fluxes leads to temperature heterogeneity in the structure and, as a result, to a cooling or heating of the junction. Within the framework of this concept, the thermoelectric cooling is analysed. It is shown that in the general case the Peltier effect always occurs together with another thermoelectric effect. This thermoelectric effect is predicted for the first time, and we have called it the barrierless thermoelectric effect. Both these effects essentially depend on the junction surface thermal resistance. The Peltier effect disappears in the limiting case of a very large surface thermal resistance, while the barrierless effect disappears in the limiting case of a very small surface thermal resistance. The dependence of thermoelectric cooling on the geometrical dimensions of the structure is noted, and the corresponding interpretation of this fact is discussed. It is shown that the thermoelectric cooling (heating) is a thermodynamically reversible process in the linear approximation of the electric current applied.

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.

The effective thermal conductivity and thermal diffusivity of a two‐layer system are investigated from the theoretical point of view for application to photoacoustic experiments. The effective thermal parameters are obtained by comparing the temperature distribution on the left or right surface of the layered structure and some effective one‐layer material. These effective thermal parameters are calculated for some special cases as for example, low and high chopper frequency. The influence of the interface thermal contact between the layers plays an important role on the effective thermal parameters. It is shown that the effective thermal conductivity and thermal diffusivity depend strongly upon the used photothermal technique.

A new approach is presented to thermoelectric phenomena, as a linear transport process of nonequilibrium charge carriers. The role of non-equilibrium carriers, as well as surface and bulk recombination, has shown to be crucial even within the linear approximation. Electron and hole Fermi quasilevels that appeared in a thermal field are calculated for the case of thermoelectric current flow through a circuit and the corresponding boundary conditions are obtained. It is shown for the first time that the Fermi quasi-level of one of the subsystems of quasi-particles, can be a non-monotonous 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, surface recombination and surface resistance were taken into account in thermoelectric phenomena.