ACOUSTOHELICON AMPLIFICATION IN A PIEZOELECTRIC SEMICONDUCTING PLASMA

Acoustohelicon amplification in semiconducting plasmas having piezoelectric or deformation potential coupling or both (viz., n-InSb) are investigated using the kinetic approach. The dispersion relation for phonon-helicon interaction is derived in slow wave approximation. In case of a convective instability the amplification occurs if the drift velocity exceeds the velocity of sound (i.e. if the electric field is greater than 10(2) Vm-1) while in case of an absolute instability amplification is observed if the drift velocity is smaller than the velocity of sound (electric field less than 10(2) V m-1). At higher electric fields (> 4.27 x 10(4) Vm-1) the amplification coefficient for acoustohelicon waves, obtained by the kinetic approach, shows a maximum and then starts attenuating, contrary to the hydrodynamic approach where it is always monotonously increasing. The dependence of the amplification coefficient on various plasma parameters is studied in detail.