Transport properties of MBE grown LaAlO$_{3}$/SrTiO$_{3}$ interfaces and the effect of stoichiometry

We report on electronic transport properties on MBE grown LaAlO$_{3}$/SrTiO$_{3}$ 2-dimensional electron gas samples measured at cryogenic temperatures in perpendicular magnetic fields. We find that the electronic properties of this system are strongly dependent on the stoichiometry of the LaAlO$_{3}$ layer: A 2-dimensional electron gas is observed only when the La/Al ratio is less than 1. Hall measurements at low-temperatures reveal that the mobility and the carrier concentration in these samples are $\sim $250 cm$^{2}$V$^{-1}$s$^{-1}$ and 10$^{13}$cm$^{-2}$ respectively. The 2-dimensional electron gas superconducts at around 200 mK. We will discuss how the low-temperature electronic properties of this oxide-oxide interface are affected by the LaAlO$_{3}$ stoichiometry.