Ga0.25In0.75As/InP quantum wells with extremely high and anisotropic two-dimensional electron gas mobilities

Measurements of modulation-doped Ga0.25In0.75As/InP quantum wells show, in the [-110] direction, a record electron mobility of 520 000 cm(2)/V s at 300 mK. A mobility difference of 15% between the [110] direction and the [-110] direction is observed. This anisotropy is tentatively attributed to an ordering effect. The mobilities at room temperature and at 77 K were 16 100 and 170 000 cm(2)/V s, respectively. By separating out the ionized impurity scattering from other scattering processes in the quantum well, we conclude that at low electron concentrations ionized impurity scattering is limiting the mobility, while alloy scattering has a strong influence on the mobility at high electron concentrations, From this result we determine the first experimental value of the alloy-scattering potential as Delta V=0.3 eV. (C) 1996 American Institute of Physics.