Excitation of Hypersound due to Coupling with Space Charge Waves of Millimeter Wave Range in Gan Films

Abstract

The excitation of hypersonic waves (f = 30-200 GHz) due to coupling with amplified space charge waves of millimeter wave range in GaN films is investigated theoretically. An amplification of space charge waves due to the negative differential conductivity in GaN films placed onto a semi-infinite substrate is considered and possible spatial increments are calculated. Both diffusion-drift equations for volume electron concentration and also an approximation of two-dimensional electron gas were used jointly with the Poisson equation for the electric field. The amplified space charge waves can excite hypersonic waves in the substrate at the same frequency due to piezoeffect and deformation potential mechanisms. It is demonstrated that the piezoeffect seems very effective for resonant excitation of hypersonic waves in the case of a full mechanic contact of GaN film and a non-piezoelectic substrate.

Active and tunable metamaterials

“…Such a power is quite possible in a pulsed regime for GaN, in particular with a pulse duration less than 1 ns [92]. It is interesting, that, as has been previously shown [93], excitation of very high-frequency ( f 30-200 GHz) hypersonic waves is possible due to coupling with amplified space-charge waves of millimeter range in GaN films. This provides a perspective for applications in the field of high-frequency acoustic metamaterials.…”