Harmonics spectra in an n-type InP bulk semiconductor
showing up to the 13th harmonic are reported. The external
field is linearly polarized with the frequency ν = 100 GHz.
Calculations are based on a Monte Carlo simulation for the
electron motion in the conducting band and on an electrodynamics
equation for the harmonics generation. The effect of a significant
reduction of efficiency in the generation of particular
harmonics is found, and is traced back to a sort of alternating
field Gunn effect. A short analysis of the different physical
mechanisms giving rise to harmonics generation is presented.