ACOUSTIC-WAVE AMPLIFICATION IN QUANTUM SEMICONDUCTOR STRUCTURES

A microscopic theory of acoustic wave amplification is presented for a n ideal, periodic array of quantum wells (superlattice) in the presenc e of an applied electric field. The effect of the external field is to produce a drift velocity of the charge carriers in the superlattice h eterostructure such that when this drift velocity exceeds the acoustic wave velocity, the confined electrons can lose energy to the acoustic wave and an acoustic amplification rather than attenuation occurs. It is shows that for these quantum semiconductor structures provided the y carl be tailored, acoustic wave amplification can occur at much larg er rate and at much lower electric fields as compared with the bulk st ructure.