Dependence of Seebeck coefficient on carrier concentration in heavily B- and P-doped Si1-xGex (x <= 0.05) system

The electrical resistivity p, the Seebeck coefficient S and the carrier mob ility mu were measured as a function of carrier concentration it for B- and P-doped Si, Si0.97Ge0.03 and Si0.95Ge0.05 prepared by are melting. It was found that at a high carrier concentration of about 2 x 10(20) cm(-3), the S values of the Si0.97Ge0.03 and Si0.95Ge0.05 samples with dopant segregati ons are about 50% higher than those measured previously on Si0.95Ge0.05, Si 0.85Ge0.15 and Si0.7Ge0.3 samples with little segregation although the diff erences between their p values are very small. The most striking result is that the S curves of the doped Si samples have a hump at a concentration of about 3 x 10(19) cm(-3), while no hump was observed for the Si0.97Ge0.03 s amples, as in the case of Si0.7Ge0.3 alloys. Such a hump is surprising beca use it conflicts with the conventional theory that predicts a monotonic dec rease of S with increasing II. This phenomenon is related to a change in th e effective mass which results from dopant segregation.