Anisotropic Electron Mobility of Two-Dimensional-Electron-Gas in Modulation Doped Inx.Ga1−y As/InyAl1−yAs Heterostructures

ABSTRACTWe have investigated the electrical properties of the two-dimensional-electron-gas (2DEG) present in strain relaxed heterojunctions with InxGa1−xAs channels (x<0.4). These were grown by molecular beam epitaxy on misoriented (001) GaAs substrates using compositionally step graded buffer layers, … x' = 0.1 per step, each step 0.3 µm thick. The 2DEG is produced by modulation doping using lattice matched InyAl1−yAs as the carrier supply layer. We find typical electron densities and mobilities, for x=0.3, of ns(300 K) = 1.3 × 1012 cm−2 and µH(300 K) = 9300 cm2/V-s; and for ns(1.6 K) = 1.2 × 1012 cm−2, µH(1.6 K) = 37800 cm2/V-s. While the room temperature electron mobility shows negligible anisotropy, an <110>-orientation dependent low temperature electron mobility of the 2DEG is observed and attributed to dislocation scattering.