Investigation of Thermoelectric Properties of Si/Ge Multilayer with Ultra-Heavily B Doping

抄録

Si/Ge and Si/GeB multilayer structured thin films were prepared by using the ion-beam sputtering (IBS) method with changing the growth temperatures from room temperature to 873 K. Then their thermoelectric properties were estimated and the effects of boron on Si/Ge superlattice structure were investigated. It was shown from XRD spectra that samples prepared below 673 K kept the periodic structure, however at exceeding 773 K the structure was broken. Si/Ge multilayer thin films showed larger thermoelectric power than that of bulk-SiGe materials and also Si/GeB multilayer showed decreases of thermoelectric power with increasing growth temperature, which is related to the increase of carrier concentration by boron activation. As for the resistivity, since the Si/GeB multilayers had lower values of the resistivity than that of Si/Ge multilayers, a boron doping effect was identified. In both Si/Ge and Si/GeB, the resistivity had a minimum at 673 K. Since the multilayer structure holds up to this temperature, the decrease in the resistivity can be attributed to the increase in the carrier mobility of the layer with a lower band gap. As a result, Si/GeB showed the larger power factor than that of Si/Ge multilayer at 673 K.