Thermoelectric Properties of Oblique SiGe Whiskers

Abstract

The effects of geometric features of p-type Si1 – xGex (x = 0.01-0.05) whiskers on their thermoelectric properties have been studied. Oblique whiskers of various diameters (10-100 μm) with boron impurity concentration ranging from 1017 to 1020 cm – 3 have been studied in the temperature range of 290-390 K. The Seebeck coefficient and resistivity of SiGe whiskers increased, while thermal conductivity decreased with decreasing diameter of crystals. However, the thermoelectric figure of merit of SiGe whiskers remained low, resembling that of bulk pure silicon. The influence of dopant impurities and germanium spatial distribution on the electronic and thermal transport in Si1 – xGex whiskers was likely dominant, however, little effect of the geometry was also observed. The engineering of whiskers shape and dimensions (up to 15 % improvement of thermopower in whiskers with certain obliquity), combined with appropriate doping, would likely allow for substantial improvement of their thermoelectric performance even in bulk-like scales.