Résumé
Experimental results of direct measurement of resonant monochromatic terahertz emission optically excited in InGaAs transistor channels are presented. The emission is attributed to two-dimensional plasma waves excited by photogeneration of electron-hole pairs in the channel at the frequency$f_0$of the beating of two cw-laser sources. The presence of resonances for the radiation emission in the range of$f_0\pm 10$GHz (with$f_0$from 0.3 up to 0.5 THz) detected by a Si-bolometer is found. Numerical results support that such a high quality of the emission resonances can be explained by the approach of an instability in the transistor channel.