In order to understand the doping behavior of extremely narrow band gap mat
erials and to optimize their characteristics for use in a thermoelectric mo
dule, we performed n- and p- type doping experiments on semiconducting Bi0.
91Sb0.09 alloy thin films using the group VI(IV) element Te(Sn) as donor (a
cceptor). Thermoelectric power (TEP), electrical resistivity, and Hall effe
ct were studied in the range of temperatures 5-300 K. Increased Sn doping c
auses the TEP to change sign (from negative to positive) and the maximum in
the TEP can be controlled with the dopant concentration. Increased Te dopi
ng causes the TEP to decrease. The maximum Te- oped electron concentration
was about 5x10(20) cm(-3) and the highest Sn-doped hole concentration was a
bout 1x10(21) cm(-3). Highly Sn- and Te-doped samples show degenerate behav
ior in the electrical resistivity, TEP and Hall measurements. (C) 1999 Amer
ican Institute of Physics. [S0021-8979(99)02707-3].