Extremely high electron mobility in isotopically-enriched 28Si two-dimensional electron gases grown by chemical vapor deposition

Both depletion-mode and enhancement-mode two-dimensional electron gases (2DEGs) in isotopically enriched 28Si with extremely high mobility (522 000 cm2/V s) are presented. The samples were grown by chemical vapor deposition using enriched silane. The fraction of the spin-carrying isotope 29Si was reduced to the level of 800 ppm by 28Si enrichment, with the electron spin dephasing time expected to be as long as 2 μs. Remote impurity charges from ionized dopants and the Si/Al2O3 interface were suggested to be the dominant source for electron scattering in the enriched 28Si 2DEGs.