Tunable Quasi-Two-Dimensional Electron Gases in Oxide Heterostructures

We report on a large electric-field response of quasi–two-dimensional electron gases generated at interfaces in epitaxial heterostructures grown from insulating oxides. These device structures are characterized by doping layers that are spatially separated from high-mobility quasi–two-dimensional electron gases and therefore present an oxide analog to semiconducting high–electron mobility transistors. By applying a gate voltage, the conductivity of the electron gases can be modulated through a quantum phase transition from an insulating to a metallic state.