Using advanced ab-initio calculations, we describe the formation and confinement of a two-dimensional electron gas in short-period (≃4 nm) Nb-doped SrTiO3 superlattices as function of Nb doping. We predict complete two-dimensional confinement for doping concentrations higher than 70%. In agreement with previous observations, we find a large thermopower enhancement at room temperature. However, this effect is primarily determined by dilution of the mobile charge over a multitude of weakly occupied bands. As a general rule, we conclude that thermopower in similar heterostructures will be more enhanced by weak, rathern than tight spatial confinement.
@article{arxiv.1309.4964,
title = {Doping-induced dimensional crossover and thermopower burst in Nb-doped SrTiO$_3$ superlattices},
author = {P. Delugas and A. Filippetti and M. J. Verstraete and I. Pallecchi and D. Marré and V. Fiorentini},
journal= {arXiv preprint arXiv:1309.4964},
year = {2013}
}