Theory of Transport Effects in Semiconductors: The Nernst Coefficient, and Its Relation to Thermoelectric Power

Abstract

A general expression for the Nernst coefficient, in terms of phenomenological parameters of the band transport equations, is derived for a two-band semiconductor for which Boltzmann statistics may be applied to the carrier distributions. The expression reduces to that given by Putley when his assumptions are made. The information obtainable from experimental values of the Nernst coefficient is discussed in the light of the expression derived in the paper. Also discussed is how this information might be supplemented from experimental values of the thermoelectric power. An expression for the latter, in terms of the phenomenological band transport parameters, is given. It reduces to that given by Johnson and Lark-Horovitz, when their assumptions are made. It is pointed out that the phonon drag effect should cause an anomaly in the Nernst coefficient corresponding to that in the thermoelectric power, and an estimate of the former anomaly is made.