Monte Carlo simulation of terahertz generation in nitrides

The conditions for microwave power generation under the quasi-periodic moti on of carriers caused by the combined action of carrier acceleration in a c onstant electric field and optical phonon emission at low temperatures are analysed by means of Monte Carlo simulations of both small- and large-signa l responses in bulk nitrides such as GaN and InN. It is shown that, as a co nsequence of the high value of the optical phonon energy and the strong ele ctron-phonon interaction, a dynamic negative differential mobility caused b y transit-time resonance occurs over a wide frequency range which covers pr actically the whole submillimetre range and persists in the THz frequency r ange up to liquid nitrogen temperature. The efficiency of the amplification and generation is found to depend nonmonotonically on: (i) the static and microwave electric field amplitudes, (ii) the generation frequency, and (ii i) the carrier concentration. Accordingly, for each generation frequency th ere exists an optimal range of parameter values. Under optimal conditions w e predict a generation efficiency of about 1-2% in the 0.5-1.5 THz frequenc y range.