High electron mobility in modulation-doped GaxIn1-xAs/AlyIn1-yAs heterostructures with highly strained AlInAs grown by molecular beam epitaxy

N-type modulation-doped Ga x In 1-x As/Al y In 1-y As 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 x In 1-x As (x=0.453) and the Al y In 1-y As (y=0.421) layers are strained. X-ray Pendellosung fringes from the Ga x In 1-x As as well as the Al y In 1-y As epilayers are observed, indicating an almost perfect interface smoothness and homogeneity of the layer composition. Despite the highly strained Al y In 1-y As the electron mobility reaches 9.0*10 3 , 6.5*10 4 , and 8.9*10 4 cm 2 V -1 s -1 at 300, 77 and 4 K, respectively, thus indicating only a minor influence of the strain of the Al y In 1-y As upon the 2D electron mobility. In photoluminescence the excellent material quality manifests itself in the narrow bound exciton peak from the Ga x In 1-x As layer and in the absence of any transition related to the 2D electrons and holes trapped near the heterointerface.