Imaging phonon drag in gallium nitride

Phonon-drag imaging has been used to study the electron-phonon interaction in a low-mobility n-type gallium nitride (GaN) epilayer grown by molecular beam epitaxy on sapphire. Currents up to j=4.7x10(3) A/m(2) were induced by transverse acoustic phonon drag of electrons in this structure. Such curre nts are much bigger than predicted by the conventional theory of electron-p honon interaction. We explain this difference by the fact that, in low-mobi lity GaN, the 2k(F) cutoff for electron-phonon transitions is relaxed. (C) 2000 American Institute of Physics. [S0003-6951(00)00847-0].