Thermoelectric properties of epitaxial Ge thin films on Si(001) with strong crystallinity dependence

Abstract

The thermoelectric properties of epitaxial Ge films on Si(001) substrates were investigated, where the film crystallinity was controlled using various growth techniques established in large-scale integration research. The films exhibited substantially lower thermal conductivities than that of bulk Ge. Unlike carrier mobility with strong crystallinity dependence, the Seebeck coefficient was similar to the high bulk value and exhibited less crystallinity dependence. This demonstrates that inherently high-carrier-mobility Ge films with high crystallinity can exhibit reduced thermal conductivity and a high thermoelectric power factor simultaneously, leading to the realization of thermoelectric films on Si for reusing low-temperature waste heat from Si-based electronic devices.