The Amplification of Hypersound by Photoelectrons in Quantizing Magnetic Field

Abstract

A new mechanism of the amplification of hypersound by inversely distributed photoelectrons of a semiconductor in quantizing magnetic field is suggested. In contrast to the traditional amplification mechanisms (by electron drift /I, 2/ o r by high-frequency electric field / 3 n in the present case the necessary condition of amplification of sound is the decrease of E*= (qz/2 + ma4/qJ /2m (8 and i n semiconductors with a n increasing region subjected to laser illumination (under capture of electrons by shallow neutral impurity centrles with emission of phonons) was considered. This mechanism of capture is considered in the first part of the present note. The monochromatic generation of c a r r i e r s i n the conduction band occurs from the valence band or from deeper centres.Let u s consider the case when in the presence of a quantizing magnetic field in a shallow potential well of small radius a discrete level arises with depth equal to Ei = (1/2)a:wH, a is a parameter characterising the interaction of electrons with the impurity, aH is the cyclotron frequency (if is supposed that in the absence of H there are no bound states in the well /6, ' I / and the lattice temperature is T e E.). We consider that the initial energy of the photoelectrons sat1 sfi es the inequality