Low Temperature High Electron Mobility in In0.75Ga0.25As/In0.75Al0.25As Modulation-Doped Hetrostructures Grown on GaAs Substrate

We have grown In0.75Ga0.25As/In0.75Al0.25As modulation-doped hetrostructure on GaAs substrate via InAlAs step-graded buffer by molecular beam epitaxy and obtained electron mobilities of 175,000 and 397,000 cm2/V·s at 77 and 4.2 K respectively, those of which are the highest ones ever reported in this materials system. Comparing the results with those of In0.75Ga0.25As/In0.66A0.34As and In0.5Ga0.5As/In0.5Al0.5As heterostructures grown similarly, it is concluded that the high mobility was attained due to the reduced alloy scattering under the strain-free interface condition and to the reduced electron effective mass (0.040m 0 from far-infrared measurement).