Effect of non-drifting hot phonons on high-field drift velocity in GaN/AlGaN

We report on the studies of steady-state high-field drift velocity in GaN/AlGaN HEMT structures. The results are compared with a model taking into account the effect of hot phonon production on the high-field transport of electrons. In the theoretical model Cerenkov effects and phonon drift are assumed to be negligible. Experimental results show that the drift velocity saturates at v(d) = 1.0 X 10(7) cm s(-1) at electric fields in excess of F approximate to 7.5 kV cm(-1) at T(L) = 77 K. Theoretical calculations indicate that the enhanced scattering rate due to the production of non-drifting hot phonons reduces the drift velocity. The reduction in the drift velocity increases with increasing population of non-drifting non-equilibrium phonons.