The growth of high mobility heterostructures on (311)B GaAs

We demonstrate that the (311)B surface of GaAs can be used for the fabrication of high mobility (μ ≅ 2.4 × 10⁶ cm² V^-1 s^-1) two-dimensional electron gases, in which the mobility is found to be anisotropic with μ_[233] > μ_[011]. This paper reviews the magneto-transport properties of the (311)B system and sheds light on the nature of the scattering mechanisms determining the electron mobility. These results are of particular relevance to the current discussion of the nature of the {311} surface. It is well known that a similar mobility anisotropy exists in hole gases grown on the (311)A surface, although attempts to interpret such results are complicated by the anisotropic and non-parabolic nature of the valence band structure. For electron gases grown on the (311)B surface we demonstrate experimentally (with ballistic focusing) that the Fermi surface is isotropic, leading to the conclusion that the most likely cause of the mobility anisotropy is anisotropic interface roughness scattering. This is also confirmed by measurements of mobility as a function of carrier density, which can be fitted by a simple interface roughness scattering theory. Further experiments have demonstrated that ballistic quantization can be observed in both [233] and [011] directions, despite the large differences in anisotropic mobility.