Thermoelectric properties of Si-Ge whiskers

Si-Ge solid solutions are known to be good high-temperature thermoelectric materials. The aim of the paper is to study the thermoelectric properties of Si-Ge (x=0.01-0.11) whiskers in temperature range 4.2-500 K. Measurements were carried out on whiskers with a boron concentration in the vicinity to metal-insulator transition from dielectric side of the transition. Temperature dependencies of Seebeck coefficient for whiskers with various resistivity (ρ=0.01-0.05 Ω cm) have been investigated. It was found that Seebeck coefficient as a rule decreases slowly at temperature growth. A slope of α(T) curves depends on whisker doping level. The α-value is about 1 mV/K, which is prospective for whisker applications in temperature sensors. To estimate an efficiency of such sensor we have calculated figure of merit Z for the whiskers. Depending on doping level the whisker figure of merit is ∼(1-2)×10−4 K−1 in the investigated temperature range. Therefore, the obtained results allow to conclude that heavily doped Si-Ge (x=0.01-0.1) whiskers can be successfully used for design of sensors for measuring of cryogenic and the above room temperatures.