Low temperature, high magnetic field magnetoresistance and Hall measurements on MBE-Grown LaAlO$_{3}$/SrTiO$_{3}$ interfaces

We have measured MBE-grown LaAlO$_{3}$/SrTiO$_{3}$ samples at temperatures ranging from room temperature to 20mK and at magnetic fields up to 18 Tesla. The La$_{(1-x)}$Al$_{(1+x)}$O$_{3}$ films studied were grown with a stoichiometry gradient (varying x). We report on the low-temperature sheet carrier density and mobility of the conducting samples -- samples with La/Al ratio less than or equal to 0.97 $\pm $ 0.03. We discuss the dependence of sheet carrier density and mobility on stoichiometry by using samples grown on the same substrate and then isolated by using a wire saw. In the devices we measured, the low-temperature sheet carrier densities are on the order of 1x10$^{13}$ cm$^{-2}$ with an approximate variation of 2x10$^{12}$cm$^{-2}$ form device to device. The mobilities observed are on the order of 1x10$^{3}$ cm$^{2}$V$^{-1}$s$^{-1}$.