Potential barrier lowering and electrical transport at the LaAlO${}_3$/SrTiO${}_3$ heterointerface

Using a combination of vertical transport measurements across and lateral transport measurements along the LaAlO${}_3$/SrTiO${}_3$ heterointerface, we demonstrate that significant potential barrier lowering and band bending are the cause of interfacial metallicity. Barrier lowering and enhanced band bending extends over 2.5 nm into LaAlO${}_3$ as well as SrTiO${}_3$. We explain origins of high-temperature carrier saturation, lower carrier concentration, and higher mobility in the sample with the thinnest LaAlO${}_3$ film on a SrTiO${}_3$ substrate. Lateral transport results suggest that parasitic interface scattering centers limit the low-temperature lateral electron mobility of the metallic channel.