Non-Reciprocal Acoustic Transmission in a GaN Delay Line Using the Acoustoelectric Effect

This letter reports on first-time demonstration of non-reciprocal acoustic transmission in a gallium nitride (GaN) delay line structure. The split of forward (S21) and backward (S12) transmissions is observed by applying a dc electric field through the active area with a two-dimensional electron gas (2DEG) sheet. The non-reciprocity (~20.7 dB/mm max. in this letter) varies by tuning the gate voltage to deplete the 2DEG sheet carrier density, which agrees with model prediction for the interaction between 2DEG and surface acoustic waves. Our preliminary results prove the feasibility of implementing chip-scale non-reciprocal acoustic devices in a GaN platform through acoustoelectric amplification.