Impurity-concentration dependence of seebeck coefficient in silicon-on-insulator layers

We measured the Seebeck coefficient of P-doped ultrathin silicon-on-insulator (SOI) layers with thicknesses of 6-100 nm. The dependence of the coefficient on the impurity concentration was investigated, and was shown to be in good agreement with that of bulk Si. In addition, it was found to decrease with increasing impurity concentration, as is usual in semiconductor materials. However, for doping levels above 3.5x1019 cm-3, the Seebeck coefficient was observed to increase. This is likely to be due to the influence of an impurity band.