Photon assisted hypersonic phonon emission from terahertz-driven two-dimensional electron gases1

A theoretical study of the generation of high-frequency acoustic phonons by electrons in GaAs-based two-dimensional (2D) electron gases (2DEGs), subject to intense terahertz (THz) electromagnetic (EM) radiations, is presented. We have studied the frequency and angular dependence of the phonon emission generated optically. The distinctive nature for electron–photon–phonon interactions in a 2DEG results in a strong dependence of the acoustic phonon emission on strength and frequency of the THz EM field. Consequently, frequency- and angle-tunable hypersonic phonon emission can be generated by varying the strength and/or frequency of the radiation field. These results are pertinent to phonon emission experiments and to the application of 2D semiconductor systems as high-frequency hypersonic sources.