Emission and absorption of phonons by the two-dimensional electron gas in a GaAs MODFET structure

The authors have observed both emission and absorption of phonons by the two-dimensional electron gas in a GaAs modulation-doped field effect transistor (MODFET). For the first time in this system directly emitted LA phonons were seen, in addition to the TA products of LO down-conversion. The angular dependence of the LA feature suggested that its origin was piezoelectric not deformation potential coupling. Direct absorption of phonons by the 2DEG was found to have a response time approximately ns, so that the transmission stop bands of a superlattice phonon fitter could be used as a dispersive spectrometer.