Dipole scattering in polarization induced two-dimensional electron gases
  Unusually large spontaneous and piezoelectric fields in the III-V nitrides have led to the making of an entirely new class of two-dimensional electron gas. Fluctuation from a perfectly periodic binary structure in highly polar semiconductor alloys present the same physical situation as a random distribution of microscopic dipoles. The excess dipole distribution in the barrier layers is evaluated by a method similar to the virtual crystal approximation. It is shown that the mobility of electrons in the two-dimensional electron gas formed in highly polar heterostructures is intrinsically limited by scattering from such dipoles. 
Debdeep Jena, Arthur. C. Gossard, Umesh. K. Mishra