Magnetotransport in the 2DEG at Interface Between LaAlO$_{3}$ and Thin Film SrTiO$_{3}$*

Transport properties of the 2DEG formed at the heterointerface between LaAlO$_{3}$ (LAO) and SrTiO$_{3}$ (STO) grown on Si and (LaAlO$_{3}$)$_{0.3}$-(Sr$_{2}$AlTaO$_{3}$)$_{0.7}$ (LSAT) were compared to those of the LAO on single crystal STO interface. The STO layer on Si was grown by molecular beam epitaxy and on LSAT by pulsed laser deposition (PLD). In all cases, the LAO overlayers were grown using PLD. Mobility, carrier concentration, and magnetoresistance (MR) were measured over the range 3-300K and magnetic fields of 0-8T. The transport properties were similar at room temperature for the different structures. However, at low temperatures, the structures on single crystal STO showed metallic behavior and positive MR, constant in temperature in the 3-20K regime, whereas the ones on Si and LSAT substrates showed a temperature dependence consistent with Mott-type variable range hopping and negative MR with power law behavior in temperature.