Influence of heavy doping on Seebeck coefficient in silicon-on-insulator

We measured the Seebeck coefficient of heavily P-doped silicon-on-insulator layers with P concentrations above 1×1019 cm−3. The coefficient decreased with increasing P concentration, and with a peak of the Seebeck coefficient around 5×1019 cm−3. We calculated the density-of-states (DOS) of bulk Si based on theoretical models of impurity-band formation, ionization-energy shift, and conduction-band tailing. The calculated impurity-concentration dependence of the energy derivative of the DOS at the Fermi energy also showed a peak. Consequently, the Seebeck coefficient of the heavily doped Si is ruled by the DOS distribution, similar to metallic materials.