High-frequency properties of systems with drifting electrons and polar optical phonons

Abstract

An analysis of interaction between drifting electrons and optical phonons in semiconductors is presented. Three physical systems are studied: three-dimensional electron gas (3DEG) in bulk material; two-dimensional electron gas (2DEG) in a quantum well, and two-dimensional electron gas in a quantum well under a metal electrode. The Euler and Poisson equations are used for studying the electron subsystem. Interaction between electrons and polar optical phonons are taken into consideration using a frequency dependence of the dielectric permittivity. As a result, the dispersion equations that describe self-consistent collective oscillations of plasmons and optical phonons are deduced. We found that interaction between electrons and optical phonons leads to instability of the electron subsystem. The considered physical systems are capable to be used as a generator or amplifier of the electromagnetic radiation in the 10 THz frequency range. The effect of instability is suppressed if damping of optical phonons and plasma oscillations is essentially strong.