Amplification of acoustic phonons in a degenerate semiconductor superlattices

Abstract

Amplification of acoustic phonons propagating along the axis of a semiconductor superlattice (SL) is investigated using the microscopic theory. A non-quantizing electric field is applied to the S to produce a drift velocity VD f the charge carriers and whenever VD exceeds v (sound velocity) amplification occurs. The threshold field EOat which absorption switches over to amplification depends on the SL, parameters and v It is noted that E in SL is by far lower than that in bulk semiconductor and that there exists the possibility of finding a field E* such that-JF(E*)Ž F7(-E*). This allows in principle the use of SL, as hypersound generator