ANISOTROPIC ROUGHNESS SCATTERING AT A HETEROSTRUCTURE INTERFACE

Anisotropic Hall mobilities of a two-dimensional electron gas are observed in modulation-doped AlxGa1-xAs/GaAs heterostructures grown by molecular-beam epitaxy on a (001) GaAs substrate. The mobility in the [110BAR] direction is larger than that in the [110] direction. An anisotropic in roughness is proposed to account for the observed anisotropic Hall mobilities.- The dependences of the anisotropic mobilities on the electron concentration are explained well by the theoretical calculation, which assumes the existence of interface islands longer in the [110BAR] direction than in the [110] direction. This assumption is consistent with previous reports on in situ measurement of growing surfaces by scanning tunneling microscope and electron diffraction.