Absence of coherence effects of carrier energy and velocity in GaAs+-AlGaAs-GaAs- tunnel structures

A Monte Carlo calculation has been performed to investigate the electron-phonon interaction and the possibility of coherent phonon emission in the buffer layer of semiconductor-insulator-semiconductor structures. Spatial coherence is shown to be virtually absent in the voltage range of tunnel-junction experiments where current structures with the period of the phonon energy have been observed. Tiny oscillations are obtained for carrier energy and velocity as a function of the gate voltage. However, the fluctuations are too weak to confirm models based on substantial periodic energy variations due to the emission of optical phonons.