Measurement of Seebeck coefficient perpendicular to SiGe superlattice

Seebeck coefficient is one of the key parameters to evaluate the performance of thermoelectric coolers. However, it is very difficult to directly measure Seebeck coefficient perpendicular to thin film devices because of the difficulty of creating a temperature gradient and measuring localized temperature and voltage change simultaneously. In this paper, a novel method is described and it is used to measure the Seebeck coefficient of SiGe superlattice material perpendicular to the layers. Successful measurement was achieved by integrating a thin film metal wire as a temperature sensor and heat source on top of the SiGe superlattice micro coolers. Extensive thermoreflectance imaging characterization was performed to ensure uniform temperature distribution on top of the thin film device. Details of the experimental set-up and measurement technique are discussed. By analyzing the measured thermoelectric voltage for various device sizes and superlattice thickness, Seebeck coefficient of the superlattice material perpendicular to the layers is deduced.