No 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.

In the common thermoelectric theory, minority charge carriers are assumed to be absent in n- or p-type thermoelectric materials. This study considers their presence and evaluates the effects of that presence on the thermo-electromotive force (Thermo-E.M.F.) of a non-degenerate n-type semiconductor. The calculations are done in the case of silicon. The contribution due to the presence of the minority holes to the total Thermo-E.M.F. depends on the thermopower of minority carriers, their electrical and thermal conductivities. It also depends on their bulk and surface recombinations and depends on the majority carriers only through their thermal and electrical conductivities. In the case of silicon, that contribution remains generally very low although it can increase or decrease the total Thermo-E.M.F. depending on the concentration of the doping elements, the bulk and surface recombination rates, and the length of the sample.