Magnetotransport measurements of charge carriers at the interface of a LaAlO3/SrTiO3 heterostructure with 26 unit cells of LaAlO3 show Hall resistance and magnetoresistance which at low and high temperatures is described by a single channel of electr
on-like charge carriers. At intermediate temperatures, we observe non-linear Hall resistance and positive magnetoresistance, establishing the presence of at least two electron-like channels with significantly different mobilities and carrier concentrations. These channels are separated by 6 meV in energy and their temperature dependent occupation and mobilities are responsible for the observed transport properties of the interface. We observe that one of the channels has a mobility that decreases with decreasing temperature, consistent with magnetic scattering in this channel.
The low-temperature resistance of a conducting LaAlO3/SrTiO3 interface with a 10 nm thick LaAlO3 film decreases by more than 50% after illumination with light of energy higher than the SrTiO3 band-gap. We explain our observations by optical excitatio
n of an additional high mobility electron channel, which is spatially separated from the photo-excited holes. After illumination, we measure a strongly non-linear Hall resistance which is governed by the concentration and mobility of the photo-excited carriers. This can be explained within a two-carrier model where illumination creates a high-mobility electron channel in addition to a low-mobility electron channel which exists before illumination.
