  We have spectroscopically determined the band offsets at epitaxial interfaces
of BaSnO3 with SrTiO3(001) and LaAlO3(001). The conduction band minimum is
lower in electron energy in the BaSnO3 than in the SrTiO3 and LaAlO3 by 0.6 +/-
0.1 eV and 3.7 +/- 0.1 eV, respectively. Thus, electrons generated in the
SrTiO3 and LaAlO3 and transferred to the BaSnO3 by modulation and polarization
doping, respectively, are expected to drift under the influence of an electric
field without undergoing impurity scattering and the associated loss of
mobility. This result bodes well for the realization of oxide-based,
high-mobility, two-dimensional electron systems that can operate at ambient
temperature.
