La-doped SrTiO3 films with large cryogenic thermoelectric power factors

The thermoelectric properties at temperatures between 10 K and 300 K of La-doped SrTiO3 thin films grown by hybrid molecular beam epitaxy (MBE) on undoped SrTiO3 substrates are reported. Below 50 K, the Seebeck coefficients exhibit very large magnitudes due to the influence of phonon drag. Combined with high carrier mobilities, exceeding 50 000 cm(2) V-1 s(-1) at 2 K for the films with the lowest carrier densities, this leads to thermoelectric power factors as high as 470 mu Wcm(-1) K-2. The results are compared with other promising low temperature thermoelectric materials and discussed in the context of coupling with phonons in the undoped substrate. (C) 2013 AIP Publishing LLC.