Electron—Hole plasma instabilities

A semiconductor plasma slab will support three classes of slow quasi-static waves: 1) bulk waves which involve space-charge disturbance throughout the bulk of a thick slab, 2) surface waves which involve surface charge disturbance along one surface of a thick slab, and 3) thin-layer waves which involve dipolar surface charge disturbance on either side of a thin plasma slab. A review of the linear stability theory for these waves indicates that each wave class can support one or more potentially unstable two-stream modes. Four of these modes should be observable in InSb: 1) a thin-layer wave interaction in the low magnetic field limit (
\omega_{ce}\tau_{e} \ll 1
), 2) a collision-induced mode supported by the thin-layer waves when
\omega_{ce}\tau_{e} \gsim 1
, 3) a corresponding collision-induced mode supported by the bulk space-charge waves when
\omega_{ce}\tau_{e} \gsim 1
, and 4) a mode which results from the interaction of surface waves. The second mode has been well documented experimentally.