Low Temperature High Electron Mobility in In_0.75Ga_0.25As/In_0.75Al_0.25As Modulation-Doped Hetrostructures Grown on GaAs Substrate

Abstract

We have grown In 0.75 Ga 0.25 As/In 0.75 Al 0.25 As 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 cm 2 /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 In 0.75 Ga 0.25 As/In 0.66 A 0.34 As and In 0.5 Ga 0.5 As/In 0.5 Al 0.5 As 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 (0.040 m 0 from far-infrared measurement).