Monte Carlo calculations of amplification spectrum for GaN THz transit-time resonance maser

The aim of this work is to calculate the amplification band and the maximum gain for an optical phonon transit-time resonance (OPTTR) maser based on bulk zincblende and wurtzite GaN. For this sake the response function of the longitudinal velocity in the time domain representation is obtained by an extended averaging over the before- and after-scattering ensembles during Monte Carlo simulations. Then the differential mobility spectrum is calculated by Fourier transformation. In the frequency region of dynamic negative differential mobility (DNDM), the gain is determined and we investigate its dependence on frequency, applied electric field, lattice temperature, and doping level.