HEATING OF 2-DIMENSIONAL ELECTRON-GAS AND LO PHONONS IN DELTA-DOPED GAAS BY FAR-INFRARED RADIATION

A change in the conductivity of the two-dimensional electron gas in de lta-doped GaAs samples due to pulsed far-infrared laser irradiation ha s been detected. It is shown that the observed positive photoconductiv ity is caused by heating of 2D electrons. The energy loss of hot elect rons is accomplished by scattering with nonequilibrium longitudinal op tical (LO) phonons. An expression for the effective emission frequency of LO phonons coupled with electrons and the thermal bath of acoustic phonons is derived and the dependence of the emission frequency on th e lattice temperature is experimentally obtained in the range 77-300 K .