  The transparent conducting oxide SnO2 is a wide bandgap semiconductor that is
easily n-type doped and widely used in various electronic and optoelectronic
applications. Experimental reports of the electron mobility of this material
vary widely depending on the growth conditions and doping concentrations. In
this work, we calculate the electron mobility of SnO2 from first principles to
examine the temperature- and doping-concentration dependence, and to elucidate
the scattering mechanisms that limit transport. We include both electron-phonon
scattering and electron-ionized impurity scattering to accurately model
scattering in a doped semiconductor. We find a strongly anisotropic mobility
that favors transport in the direction parallel to the c-axis. At room
temperature and intrinsic carrier concentrations, the low-energy polar-optical
phonon modes dominate scattering, while ionized-impurity scattering dominates
above 10^18 cm^-3.
