  A theory of scattering by charged dislocation lines in a two-dimensional
electron gas (2DEG) is developed. The theory is directed towards understanding
transport in AlGaN/GaN high-electron-mobility transistors (HEMT), which have a
large number of line dislocations piercing through the 2DEG. The scattering
time due to dislocations is derived for a 2DEG in closed form. This work
identifies dislocation scattering as a mobility-limiting scattering mechanism
in 2DEGs with high dislocation densities. The insensitivity of the 2DEG (as
compared to bulk) to dislocation scattering is explained by the theory.
