Piezoelectric coupling constant in epitaxial Mg-doped GaN

Although surface acoustic wave (SAW) devices using quartz and LiNbO
³
have proven highly successful, manufacturability would be considerably eased if SAW devices could be readily integrated with semiconductor devices. In a recent paper, Lee et al. proposed Mg-doped epitaxial GaN as suitable for SAW devices integrated with other III-V materials. The piezoelectric constant, or electromechanical coupling factor (k
₂
), is one important parameter determining the acoustic behavior of a material. A large k
₂
eases the design of wide-bandwidth low-loss SAW transducers. The piezoelectric constants are also of great interest in the design of strained-layer devices. For Mg-doped GaN, Lee et al. found k
₂
= (4.3 plusmn 0.3)%. If confirmed, this would represent one of the highest values of k
₂
ever reported, and would revolutionize the design of acoustic devices integrated with III-V materials, since other III-V materials have much smaller k
₂
. For example, GaAs has k
₂
= 0.04%