Influence of nonlocality on amplification of space charge waves in n-GaN films

Amplification of space charge waves (SCW) due to the negative differential conductivity (NDC) in n-GaN films of submicron thicknesses is investigated theoretically. An influence of nonlocal dependence of average electron velocity on the electron energy is considered. The simplest nonlocal model is used where the total electron concentration is taken into account. The relaxation momentum and energy frequencies have been calculated. An influence of nonlocality on NDC results in the decrease of absolute value of its real part and appearance of the imaginary part. The simulations of spatial increments of amplification of SCW demonstrate that nonlocality is essential at frequencies f ≥ 100 GHz, and amplification is possible up till the frequencies f ≤ 400...500 GHz.