Role of minority charge carriers in the formation of the thermo-electromotive force in p-type silicon

Abstract

The contribution of minority charge carriers (electrons) is taken into account in the evaluation of thermo-electromotive force (thermo-E.M.F.) of a non-degenerate p-type semiconductor in the stationary state and when the quasi-neutrality condition is fulfilled. The results obtained show that the contribution to the thermo-E.M.F. due to the presence of minority electrons is a function of the bandgap and the length of the semiconductor used. It also depends on the minority carriers through their electrical conductivity, thermal conductivity, Seebeck coefficient, and bulk and surface recombinations. That contribution tends to reduce the principal thermo-E.M.F. (αpΔT) of the p-type semiconductor and will, therefore, be called counter-thermo-electromotive force (counter-thermo-E.M.F.). The calculations made in the case of silicon give a counter-thermo-E.M.F. of magnitude generally non-negligible, which decreases when the length of the silicon and the concentration of doping elements increase. Finally, it is shown that the best way to minimize the counter-thermo-E.M.F. is to treat the surface of the semiconductor to promote the recombination of minority carriers there.