Thin-film boron-doped polycrystalline silicon(70%)-germanium(30%) for thermopiles

CMOS-compatible thermopiles can be made by using the available polysilicon layer and aluminium layer as a thermocouple. SiGe would, however, offer a better performance than silicon, mostly due to its much lower thermal conductivity, while it maintains CMOS compatibility. The figure of merit of a highly boron doped (about 10(20) atoms cm(-3)) thin-film poly-Si70%Ge30%, layer deposited by ultra-low-pressure chemical vapour deposition (ULPCVD) is reported. The figure of merit is measured with a dedicated structure: the Seebeck coefficient is +/-75 mu V K-1, the thermal conductivity is +/-4.8 W mK(-1) and the electrical resistivity is 23 mu Omega m. The figure of merit is then calculated to be z approximate to 50 X 10(-6) K-1.