Two-Dimensional Electron Gas at the N-type Interface of the LaAlO₃/SrTiO₃ Hetero-Structure: A First Principle Study

We examine the formation of the two-dimensional electron gas (2-DEG) at the n-type interface of two band insulators LaAlO₃ (LAO) and SrTiO₃ (STO) by increasing the thickness of the LAO layers in the framework of the density functional theory (DFT). It has been shown that a metal-insulator phase transition occurs in the 2-DEG when the LAO layers reach to a critical thickness d_c = 4 monolayers. The increase of the LAO layers enhances the LAO potential so that electrons can transfer from the LAO valence band to the STO conduction band, which confines conducting electrons only in the STO substrate.