Thermoelectric Si(1-x)Ge(x) and PbTe thin films for device applications

In order to realize thermoelectric devices for sensors, coolers and energy conversion systems the technology of preparation of thin film thermoelectric materials has to be developed. We describe the preparation of thin films of the widely used thermoelectric materials PbTe and Si(1-x)Ge(x) on different substrates by sputtering and PECVD. We report on the composition, morphology and thermoelectric data of the deposited materials. Technological steps such as etching and contacting are described. Polycrystalline boron doped Si(1-x)Ge(x) films deposited by PECVD on Si/SiO2 and Si/Si3N4 wafers with typical film thickness of 0.5-1.0 microns reach about 70% of the power factor of corresponding single crystalline materials (about 12 myW/cmK(exp 2) at room temperature after optimized annealing procedures. N-type PbTe thin films are deposited on and Si/Si3N4 wafers and on polymer foils (polyimide) by sputtering. First results show that power factors are about 13 myW/cm(K exp2). Composition and morphology of PbTe films were analyzed by x-ray diffraction before and after post deposition procedures. PbTe as well as SiGe films were structured photolithographically and subsequently wet chemical or dry ion etched. The corresponding p- or n-type legs were realized by evaporation as well as sputtering. First steps in manufacturing devices have been taken.