A change in the conductivity of the two-dimensional electron gas in δ-doped GaAs samples due to pulsed far-infrared laser irradiation has been detected. It is shown that the observed positive photoconductivity is caused by heating of 2D electrons. The energy loss of hot electrons is accomplished by scattering with nonequilibrium longitudinal optical (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 the lattice temperature is experimentally obtained in the range 77–300 K.