Use of superlattices to realize inverted GaAs/AlGaAs heterojunctions with low-temperature mobility of 2×10⁶ cm²/V s

Reproducible realization of high quality inverted interfaces (GaAs on AlGaAs) grown by molecular beam epitaxy is reported. Effective use of thin-layer GaAs/AlAs superlattices in place of an AlGaAs barrier was made to reduce the number of impurities and the roughness at these interfaces. The low-temperature (≅4 K) mobility for electrons at these interfaces is as high as 2×106 cm2/V s for an electron density of ≅5×1011 cm-2 - a factor of four improvement over the highest mobility reported for inverted interfaces.