HIGH ELECTRON-MOBILITY IN MODULATION-DOPED GAXIN1-XAS/ALYIN1-YAS HETEROSTRUCTURES WITH HIGHLY STRAINED ALLNAS GROWN BY MOLECULAR-BEAM EPITAXY

N-type modulation-doped GaxIn1-xAs/Al yIn1-yAs heterostructures grown by molecular beam epitaxy on InP substrate have been characterised by double-crystal X-ray diffraction and X-ray topography, temperature-dependent Hall measurements, and photoluminescence and absorption spectroscopy. Both the constituent Ga xIn1-xAs (x=0.453) and the AlyIn 1-yAs (y=0.421) layers are strained. X-ray Pendellosung fringes from the GaxIn1-xAs as well as the AlyIn 1-yAs epilayers are observed, indicating an almost perfect interface smoothness and homogeneity of the layer composition. Despite the highly strained AlyIn1-yAs the electron mobility reaches 9.0*103, 6.5*104, and 8.9*104 cm2 V-1 s-1 at 300, 77 and 4 K, respectively, thus indicating only a minor influence of the strain of the Al yIn1-yAs upon the 2D electron mobility. In photoluminescence the excellent material quality manifests itself in the narrow bound exciton peak from the GaxIn1-xAs layer and in the absence of any transition related to the 2D electrons and holes trapped near the heterointerface.