Amplification of space charge waves in n-InN films of THz range

The instability of space charge waves (SCW) of THz range due to the negative differential conductivity (NDC) in n-InN films of submicron thicknesses is investigated theoretically. The influence of the nonlocal dependence of the average electron velocity on the electron energy is considered. The momentum and energy relaxation frequencies are calculated. The influence of the nonlocality on NDC decreases the absolute value of its real part. The nonlocality is essential at the frequencies f ≥ 250 GHz, and the amplification is possible up till the frequencies f ≤ 800 GHz. The increments in n-InN films are 10 times higher than in n-GaN ones, but the frequency range is mainly determined by smaller energy relaxation frequencies in n-InN.