Thermoelectric characteristics of Si/Ge superlattice thin film at low temperature

We have been studied thermoelectric characteristics of Si/(Au-doped Ge) superlattice thin films at temperatures from room temperature (RT) to low temperatures less than 100 K and compared these to those of Si and (Au+Ge) alloy thin film. In the Si/(Ge+Au) superlattice after heating process the electric resistivity decreased at all temperature. This annealed Si/(Ge+Au) superlattice showed the high thermoelectric power of 105 μV/K at 290 K, compared with the unannealed Si/(Ge+Au) or the alloy film. At temperatures less than 200 K, however, the thermoelectric power of the unannealed Si/(Ge+Au) switched polarities from positive to negative and reached -4.6 mV/K at 80 K. This large negative thermoelectric power at low temperature was not observed in the annealed Si/(Ge+Au) or the alloy film. On the other hand, magnetic field characteristics of all samples showed no effect at 100 K, 200 K or 290 K. This was explained using the two-band parabolic model calculation, assuming that a large amount of Au-doping caused a very low carrier mobility.