High mobility approaching the intrinsic limit in Ta-doped SnO2 films epitaxially grown on TiO2 (001) substrates

Achieving high mobility in SnO2, which is a typical wide gap oxide semiconductor, has been pursued extensively for device applications such as field effect transistors, gas sensors, and transparent electrodes. In this study, we investigated the transport properties of lightly Ta-doped SnO2 (Sn1-xTaxO2, TTO) thin films epitaxially grown on TiO2 (001) substrates by pulsed laser deposition. The carrier density (n(e)) of the TTO films was systematically controlled by x. Optimized TTO (x=3 x 10(-3)) films with n(e) similar to 1 x 10(20)cm(-3) exhibited a very high Hall mobility (mu(H)) of 130 cm(2)V(-1)s(-1) at room temperature, which is the highest among SnO2 films thus far reported. The mu(H) value coincided well with the intrinsic limit of mu(H) calculated on the assumption that only phonon and ionized impurities contribute to the carrier scattering. The suppressed grain-boundary scattering might be explained by the reduced density of the {101} crystallographic shear planes.