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

Abstract

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.

Boundary conditions in a real bipolar semiconductor-metal junction

“…[1][2][3]. Usually every emf is measured across the metallic contacts placed on the sample surfaces.…”

Influence of energy band distortion on the Hall emf in bipolar semiconductors

“…Taking into consideration that the diffusion length significantly exceeds the Debye length we obtain the solution of Eqs. (1), (2), and (6) as a sum of two modes [3]: diffusion-recombination (DR) mode and screening (S) mode. These modes are denoted by subscripts R and S accordingly:…”

“…The above-mentioned causes have influence on the Hall emf value. This influence may be taken into account in the framework of quasi-neutrality approximation (by analogy with the thermo-emf [3]). Besides that, the distortion of energy bands [4] creates the equilibrium built-in electric field.…”

Space Charge and Transport of Nonequilibrium Carriers in Bipolar Semiconductors

“…general case for a non degenerate semiconductor, in linear approximation δn and δp can be written in terms of the variations of their respective chemical potentials as[13]:…”

“…It immediately follows that since the subsystem of two equations for the electrochemical potentials is explicitly independent of the electrical potential, the Poisson equation(2)is decoupled from (19.a) and (19.b).The fact that the Poisson equation can be decoupled from the transport ones is very important.Let us recall that the calculation of the current density in a semiconductor only involves the derivative of the electrochemical potential and no other magnitudes (see Eqs (13),. (14).…”