Hot-phonon temperature and lifetime in a biasedAlxGa1−xN/GaNchannel estimated from noise analysis

Abstract

The short-time-domain gated radiometric microwave noise technique is developed for the investigation of hot phonons in a two-dimensional electron gas channel subjected to a strong electric field applied in the plane of electron confinement. Nominally undoped pseudomorphic ${\mathrm{Al}}_{0.15}{\mathrm{Ga}}_{0.85}\mathrm{N}/\mathrm{G}\mathrm{a}\mathrm{N}$ channels are considered in the field range where LO-phonon emission by hot electrons and hot LO-phonon disintegration are mainly responsible for the energy dissipation. At a 5 kV/cm electric field, the equivalent temperature of the emitted LO phonons reaches 590 and 460 K at 80 and 293 K ambient temperatures, respectively. The electrons and emitted LO phonons form a nonequilibrium electron--LO-phonon subsystem characterized by a temperature different from that of the remaining phonons. The LO-phonon lifetime for their disintegration into the acoustic and other phonons is $350\ifmmode\pm\else\textpm\fi{}100\mathrm{fs};$ the lifetime is almost independent of the hot-phonon and ambient temperatures. The deduced value of the LO-phonon lifetime is used as an input parameter for Monte Carlo simulation of the hot-phonon effect on the two-dimensional electron transport in the biased channel, and a reasonable agreement with the experimental current-voltage characteristics is obtained.