Thermoelectric and Thermal Properties

Abstract

In the presence of a temperature gradient VT, the distribution of carrier velocities varies across a semiconductor. Consequently, even in the absence of an electric field, a macroscopic carrier flux is produced because the temperature gradient acts as an effective temperature field, which has some of the effects of the electric field. If the circuit is open and there is no current, an electric field is produced at each point in the sample and this field is found from the condition that the thermal current must be balanced by the ohmic current. The temperature gradient thus generates an electric field which gives rise to a thermo-emf or the Seebeck effect. Carriers with higher energies move from the hotter to the colder parts of the sample, and those with lower energies move in the opposite direction so that the total current is equal to zero.