Thermoelectric Inorganic SiGe Film Synthesized on Flexible Plastic Substrate

For developing thermoelectric thin-film devices using reliable inorganic materials, we investigated the synthesis of SiGe directly onto insulating substrates. An Al-induced layer exchange technique was employed, which enabled us to form SiGe on glass substrates at a low temperature (≤400 °C) in the whole SiGe composition range. The SiGe layers were observed to contain Al atoms in concentrations corresponding to their solid solubility limits during growth, which resulted in the formation of self-organically highly p-doped layers without requiring high-temperature-activation annealing. Results indicated that a high power factor (430 μW/mK2) and a low process temperature were simultaneously achieved for SiGe on glass. A SiGe layer fabricated on a plastic substrate exhibited a power factor of 190 μW/mK2, which is higher than most thermoelectric films directly grown onto a plastic substrate. These achievements will present practical applications for flexible thin-film thermoelectrics with a high reliability.