Variation of Seebeck coefficient in ultrathin si layer by tuning its Fermi energy

Abstract

We have varied the Seebeck coefficient of n-type ultrathin Si-on-insulator (SOI) layer by tuning the Fermi energy. The Fermi energy was tuned by doping P atoms into the SOI layer and by injecting carriers by applying an external bias to the SOI surface with respect to the p-Si substrate. It was found that the Seebeck coefficient decreases with increasing the impurity concentration, with a peak around 1× 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−3</sup> From the calculated density-of-states (DOS), it is considered that the peak in Seebeck coefficient is likely to be due to the formation of impurity band near the conduction-band edge, which will demolish the sharp features in low-dimensional DOS. On the other hand, the Seebeck coefficient is found to increase with increasing the external bias which is in agreement with the variation of carrier concentration in the SOI layer under external bias and it is found that the Fermi energy can be controlled without the influences of impurity band.