Sensitivity of two-dimensional electron gas to far infrared radiation

The strong photoeffect was discovered experimentally in specially doped InSe crystals at temperature 4.2 K as a result of laser radiation action at fixed wave-lengths of 337 and 195 microns.Also some of the kinetic, galvanomagnetic and optical anomalies had been observed. They are explained by appearance of the gap E in the conduction band continuum of degenerated 2D semiconductor in charge density waves state. The long wave threshold of photocurrent was found to depend strongly on a magnitude of electric current through the crystal. A rough estimation gives a value dE/dJ approximately 0.4 meV/mA. We had carried out experiments in order to study instabilities of InSe electrical properties in temperature range 4.2 approximately 300 K by quasi stationary conditions. Abrupt electrical resistivity increases about 5 times were observed by us at temperatures 5, 10, 14, 27, 31, 170 and 200 K. The frequency dispersion of conductivity for high frequencies were observed.