X-Ray Scattering Study of Phonon Amplification inn-GaAs: Plasma Effect

Abstract

Under conditions of q l >1 and ω p τ>1, acousto-electrically amplified phonons are spectroscopically studied in n -GaAS at 77 K by the X-ray Brillouin scattering, where q is the phonon wave number, l the electron mean free path, ω p the plasma frequency and τ the electron collision time. The observed maximum gain frequencies in weak signal regime are compared with theoretical ones. It is found that the observed value for sample with carrier concentration of ∼10 16 cm -3 deviates from the calculated value based upon the ordinary phonon amplification process. This deviation is qualitatively explained in terms of the plasma enhancement of the phonon amplification. The phonon spectra in strong signal regime and the shape of the phonon-flux domain are also observed.