Enhancement of the third harmonic generation efficiency in n-type Si and InP by cooling from room temperature to 80K

With the aim of developing a powerful cw source at 1 THz for studies of a-particles in thermonuclear plasmas, we investigate the third harmonic generation efficiency in semiconductors. Two Monte Carlo codes have been developed in order to predict the harmonic generation of a sample placed in an oscillating electric field. The first one is used for elemental crystals and the second one for semiconductors of the compound A(3)B(5). Experimental studies have also been performed at 9.43 GHz. In this paper we point out the enhancement of more than two orders of magnitude of the third harmonic efficiency by cooling the semiconductor down to liquid nitrogen temperature. An efficiency maximum depending on the electric field amplitude is also clearly identified. A comparison between the experiments and the simulation shows that the Monte Carlo simulations are able to predict the maximum efficiency as well as the improvement of the third harmonic generation by decreasing the temperature.