Electron scattering in AlGaN/GaN heterostructures with a two-dimensional electron gas

The temperature and concentration dependences of electron mobility in AlGaN/GaN hetero-structures are studied. The mobility for the samples under study at $T$ = 300 K lies in the range of 450–1740 cm$^2$/(V s). It is established that scattering at charged centers is dominant for samples with low mobility (lower than 1000 cm$^2$/(V s) right up to room temperature. These centers are associated with a disordered piezoelectric charge at the heterointerface because of its roughness or with a piezoelectric charge similarly to the Al–GaN barrier because of alloy disorder, as well as with the deformation field around dislocations. Scattering at optical phonons is dominant for samples with mobility exceeding 1000 cm$^2$/(V s) at $T$ = 300 K. Scattering at alloy disorders, heterointerface roughness, and dislocations are dominant at temperatures lower than 200 K. A decrease in the influence of scattering at roughness with improvement of the heterointerface morphology increases room-temperature mobility from 1400 cm$^2$/(V s) to 1700 cm$^2$/(V s).