High-Mobility Two-Dimensional Electron Gases at ZnO/ZnMgO Interfaces for Ultra-Fast Electronics Applications

We have measured high mobility electron transport at the interface between insulating zinc oxide and zinc magnesium oxide films grown by molecular beam epitaxy. A maximum electron mobility exceeding 2200 square cm V(to the -1) s(to the -1) was measured. Spectroscopic depth-profiling of the films shows however that these high mobilities can only be obtained in films where the spatial variation of the magnesium content does not show a sharp discontinuity at the interface. This suggests that higher mobilities can be obtained in the future by controlling the competing effects of interface strain and electron confinement. Ongoing work therefore will focus on tailoring the properties of the interface during growth so as to simultaneously maximise the electron confinement and minimise the strain. This will necessitate the growth of a thin film of ZnO between the ZnO single crystal substrate and the ZnMgO thin film. The original document contains color images.