Formation of 2DEG at the interface of unconventional oxide hetero-structures by atomic layer deposition.

Two-dimensional electron gases (2DEGs) with a sheet carrier density of 10$^{\mathrm{14}}$ cm$^{\mathrm{-2}}$ and high electron mobility have been realized at the interface of SrTiO$_{\mathrm{3}}$ and Al$_{\mathrm{2}}$O$_{\mathrm{3}}$ films grown by atomic layer deposition at very low temperatures. Possible origins for the high electron densities will be discussed. By controlling the interface, the sheet resistance exhibited a wide range of change from 10$^{\mathrm{3}}$ to 10$^{\mathrm{13\thinspace }}\Omega $/square. Temperature dependent Hall-effect measurements revealed metallic conduction and metal-semiconductor transitions. The effect of growth parameters, surface conditions, and film thickness on the transport properties of the interface will be discussed.