Small-angle scattering in two-dimensional electron gases

Mobilities and quantum lifetimes have been measured in a selection of two-dimensional (2D) electron gases with spacer layers between 1.5 and 40 nm and mobilities up to 180 ${\mathrm{m}}^{2}$/V s. Dingle plots (used to determine the quantum lifetime) were sometimes nonlinear, clearly indicating inhomogeneities in the 2D electron gases. For samples with good Dingle plots, the quantum lifetimes were roughly 10 times longer than is predicted by conventional calculations. The discrepancy is attributed to the treatment in these calculations of the small-angle-scattering events associated with the remote ionized donors. A modified calculation in which correlations between the small-angle-scattering events are considered provides better agreement with experiment for both the quantum lifetimes and the mobilities.