GaN Switchable Lamb Wave Delay Lines: Simulation, Fabrication and Characterization

In this paper, we report a switchable Lamb wave delay line structure based on AlGaN/GaN heterojunction with ON/OFF ratio > 30dB. The high-density two-dimensional electron gas (2DEG) in the AlGaN/GaN heterojunction channel is used to shield the piezoelectric polarized electric field and realize the delay line switch. The mechanical and electrical coupling coefficients of the Lamb wave resonator in the zero-order symmetric (S0) and anti-symmetric (A0) mods are explored by changing different thickness and wavelength ratios (h
GaN/λ
), and then the working frequency of the delay line is determined. The sample test shows that the insertion loss of the delay line in the ON state is less than 1dB worse than that of the delay line without the AlGaN layer, that is, without switchability. In addition, the finite-element simulation model for the switchable delay lines are developed and verified by the simulations.