Cerenkov acoustic-phonon emission generated electrically from a polar semiconductor

Abstract

We present a systematic theoretical study of the Cerenkov acoustic-phonon emission from a polar semiconductor such as GaAs driven by dc electric field. The drift electron velocity and electron-temperature in the system are determined by solving self-consistently the momentum- and energy-balance equations derived from the Boltzmann equation. The intensity of the phonon emission via piezoelectric and deformation-potential coupling is evaluated on the basis of the energy-balance equation. We find that the electron velocity exceeds the sound velocity in GaAs even when electrons are still in the linear response regime. This implies that the Cerenkov phonon emission can be easily observed in GaAs-based electron gas systems. We also examine the frequency and angular dependence of the acoustic-phonon emission on the applied electric field and find that our results are in line with those observed experimentally. This study is pertinent to electrical generation of acoustic-phonon sources from polar semiconductor systems.