High-mobility inverted modulation-doped GaAs/AlGaAs heterostructures

High-quality inverted GaAs/AlGaAs modulation-doped heterostructures have been grown by MBE. An AlAs/GaAs superlattice buffer layer is grown below the AlGaAs spacer layer to improve the morphology at the inverted heterointerface. An atomic layer doping and a thick spacer layer are adopted to alleviate the scattering by ionized donors. The observed electron mobility at 1.5 K is 4.3×106 cm2/Vs at a 2D electron density of 2.8×1011/cm2. Two 2D electron channels; one formed at the inverted interface and the other at the normal interface are found to be operative in the observed characteristic. The electron mobility in the inverted channel is estimated to be as high as 4.9×106 cm2/Vs at an electron density of 2.2×1011/cm2, while, in the normal channel, it is 2.1×106 cm2/Vs at a density of 6×1010/cm2.