On the role of the bulk and surface recombination in the thermopower in bipolar semiconductors

The physical transparency of thermopower phenomenon in unipolar case and the clearness of calculation lead to the following paradoxical results: in the case of a bipolar medium the situation seems to be equally obvious, and so the same calculation scheme is used. The aim of this paper is to show that situation changes in bipolar media in principle. If a semiconductor specimen contacts with a heater with temperature T/sub 1/ on the surface x=-a and with a cooler with temperature T/sub 2/ on the surface x=+a, the chemical potential of the electrons and holes are heterogeneous in space and different in all points of the specimen. Thus there are two Fermi quasilevels even in the quasineutrality approximation, and single common "gradient of electrochemical potential" of electrons and holes is absent. One more problem arises when bulk and surface recombinations take place: the correct determination of electron and hole equilibrium concentrations and boundary conditions when thermoelectric current flows in a closed circuit. The aims of this paper are to show the methods of thermopower calculations in case mentioned above and which physical phenomena determine its value.