THERMOELECTRIC AMPLIFICATION OF PHONONS IN BULK SEMICONDUCTORS UNDER A STRONG MAGNETIC-FIELD

We consider the problem of phonon instability in an electron-phonon sy stem of a semiconductor in a temperature field upon variation of a str ong (quantizing) static magnetic field. It is found that the phonons m ay become unstable when certain values for the temperature gradient-dr ift velocity and the magnetic field are exceeded. However, even after the thresholds are exceeded, it is predicted that there exist alternat e bands of the magnetic field, in which the phonons are unstable in on e band, stable in the next band, unstable again in the following band, etc. These alternate bands have their origin in the discreteness of t he Landau levels of the electrons. An application is made for a GaAs s ample. (C) 1996 American Institute of Physics.