  We report the thermoelectric properties (Seebeck coefficient, thermal
conductivity, and electrical resistivity) of lightly doped single crystals of
(001)-oriented SrTiO3 (STO). Hall effect measurements show that electron doping
around 10^-5 carriers per unit cell can be achieved by vacuum annealing of the
crystals under carefully controlled conditions. The steep density of states
near the Fermi energy of STO at this doping level (confirmed by ab initio
calculations) retains an unusually large Seebeck coefficient, in spite of an
increase in the electronic conductivity by several orders of magnitude. This
effect, combined with a decrease in thermal conductivity due to vacancy
disorder scattering makes intrinsic doping in STO (and other materials) an
alternative strategy to optimize its thermoelectric figure of merit.
