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.