Observation of energy loss by a hot two-dimensional electron gas into coupled plasmon-phonon modes

We observed the phonons emitted by a two-dimensional electron gas in GaAs/A lGaAs heterojunctions for various carrier concentrations, by a nanosecond p ulse technique. We found that the feature which has usually been regarded a s the crossover from acoustic to optic phonon emission then occurred at dif ferent power levels. We propose that a process of energy loss via excitatio n of coupled plasmon-optic phonon modes can explain this and other results, notably the weakness of the longitudinal mode observed, and the high value of the measured energy loss. (C) 1999 Elsevier Science B.V. All rights res erved.