Transport anisotropy in InGaAs 2D electron gases

Low temperature electron mobility of a 2D electron gas, formed in a 20 nm thick In0.75Ga0.25As/In0.75Al0.25As Quantum Well grown on a (0 0 1) GaAs substrate, shows a pronounced difference between the [1 1 0] and the [1 View the MathML source 0] crystallographic directions. This anisotropy cannot be explained by the traditional models for the roughness scattering. A promising candidate as the mobility limiting mechanism is the conduction band energy modulation, correlated to the surface roughness. Using the Landauer approach based on the numerical solution of the Schrödinger equation, an estimation of the conductance along the two directions can be obtained and a theoretical explanation of the anisotropy can be made. The dependence of the conductance upon the length of the device is also investigated.