EN
Experimental results of direct measurement of resonant terahertz emission optically excited in InGaAs HEMT channels are presented. The emission was attributed to two-dimensional plasma waves excited by photogeneration of electron-hole pairs in the HEMT channel at the frequency of the beating of two cw-laser sources. The presence of resonances for the radiation emission in the range of f_0 ± 10 GHz (with f_0 from 0.3 up to 0.5 THz) detected by a Si-bolometer is found. The intensity of THz emission exhibits a nonlinear growth with increase of the pumping power.