Observation of hot-electron energy loss through the emission of phonon-plasmon coupled modes in GaAs

We have directly observed hot-electron energy loss through the emission of phonon-plasmon coupled modes in n-type Si-doped GaAs. The self-compensation of silicon in GaAs was exploited to allow observation of hot-electron recombination with neutral Si acceptors in a high background concentration of free electrons. We have obtained hot-luminescence data which exhibit a peak due to the initial unrelaxed hot electrons followed by a peak lower in energy by the ${\mathit{L}}^{+}$ coupled-mode energy. The lower-energy peak corresponds to hot-electron relaxation via emission of a phonon-plasmon coupled mode. The observed peak agrees well with energy-loss calculations.