HIGH-MOBILITY INVERTED MODULATION-DOPED GAAS ALGAAS HETEROSTRUCTURES/

High-quality inverted GaAs/AlGaAs modulation-doped heterostructures ha ve been grown by MBE. An AlAs/GaAs superlattice buffer layer is grown below the AlGaAs spacer layer to improve the morphology at the inverte d heterointerface. An atomic layer doping and a thick spacer layer are adopted to alleviate the scattering by ionized donors. The observed e lectron mobility at 1.5 K is 4.3 x 10(6) cm(2)/Vs at a 2D electron den sity of 2.8x10(11)/cm(2). 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 x 10(6) cm(2)/V s at an electron density of 2.2 x 10(11)/cm(2), while, in the normal c hannel, it is 2.1 x 10(6) cm(2)/Vs at a density of 6 x 10(10)/cm(2).