We study the mobility of a two-dimensional electron gas (2DEG) which forms at an inverted GaAs/AlAs interface, in a structure where a back gate and a front gate are both used to modify the density of the 2DEG. The availability of two different control voltages provides a special opportunity to gain insight into the scattering mechanisms. We find that we can induce a significant change in the mobility, at a fixed density, by changing the interface roughness scattering, which depends on the perpendicular electric field acting on the 2DEG. We also find different mobility changes for current flowing in different directions in the plane of the 2DEG. We conclude that the roughness of the interface where the 2DEG resides is anisotropic, and it is responsible for the consistent anisotropy of the mobility in the (100) plane. We also develop a theoretical framework to calculate scattering due to anisotropic roughness.
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