Cerenkov generation of high-frequency confined acoustic phonons in quantum wells

TL;DR

This paper investigates how drifting electrons in quantum wells can generate and amplify high-frequency confined acoustic phonons through Cerenkov emission, with potential for sub-THz phonon amplification.

Contribution

It provides a general formula for the phonon gain coefficient and demonstrates significant amplification in Si/SiGe/Si quantum well structures.

Findings

Gain coefficient increases sharply at short wavelengths

Amplification of hundreds of 1/cm in sub-THz range

Potential for high-frequency phonon generation in quantum wells

Abstract

We analyze the Cerenkov emission of high-frequency confined acoustic phonons by drifting electrons in a quantum well. We find that the electron drift can cause strong phonon amplification (generation). A general formula for the gain coefficient, alpha, is obtained as a function of the phonon frequency and the structure parameters. The gain coefficient increases sharply in the short-wave region. For the example of a Si/SiGe/Si device it is shown that the amplification coefficients of the order of hundreds of 1/cm can be achieved in the sub-THz frequency range.