Mobility anisotropy of two-dimensional hole systems in (311)A GaAs/Al _xGa_1-xAs heterojunctions

We have measured the low-temperature mobility of high-quality two-dimensional hole systems confined at the (311)A GaAs/Al_xGa _1-xAs interface. Variables were the thickness of the spacer layer separating the carriers from the Si dopants, and the carrier sheet density. A large anisotropy in mobility is found between the [2̄33] and [011̄] directions. While the high mobility [2̄33] direction yields results analogous to the two-dimensional electron case, we conclude that transport along [011̄] is almost entirely determined by anisotropic interface roughness scattering.