Dependence of Seebeck Coefficient on Carrier Concentration in Heavily B- and P-Doped Si_<1-x>Ge_x (x≦0.05) System

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The electrical resistivity ρ, the Seebeck coefficient S and the carrier mobility μ were measured as a function of carrier concentration n for B- and P-doped Si, Si_<0.97>Ge_<0.03> and Si_<0.95>Ge_<0.05> prepared by arc melting. It was found that at a high carrier concentration of about 2×10^<20> cm^<-3>, the S values of the Si_<0.97>Ge_<0.03> and Si_<0.95>Ge_<0.05> samples with dopant segregations are about 50% higher than those measured previously on Si_<0.95>Ge_<0.05>, Si_<0.85>Ge_<0.15> and Si_<0.7>Ge_<0.3> samples with little segregation, although the differences between their ρ 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 3×10^<19> cm^<-3>, while no hump was observed for the Si_<0.97>Ge_<0.03> samples, as in the case of Si_<0.7>Ge_<0.3> alloys. Such a hump is surprising because it conflicts with the conventional theory that predicts a monotonic decrease of S with increasing n. This phenomenon is related to a change in the effective mass which results from dopant segregation.
社団法人応用物理学会の論文
1999-11-15