Guided elastic waves in GaN-on-sapphire

Electromechanical Coupling Coefficient for Surface Acoustic Waves in GaN-on-Sapphire

“…This result is consistent with the data reported in Refs. [1,2], and is inconsistent with much higher values of K 2 reported in Refs. [3,4].…”

“…The electromechanical coupling coefficient for SAWs can be expressed as K 2 ¼ 2DV=V, where DV is the magnitude of the SAW velocity change that occurs when the free surface of the piezoelectric is shorted by a thin highly conducting metal film, and V is the unperturbed SAW velocity. The K 2 values for SAWs in GaN-on-sapphire structures have been evaluated from transducer performance analysis and extracted from the velocity measurements by several authors [1][2][3][4]. However, there is a considerable disagreement in the results, and further investigations are necessary.…”

“…The calculations were performed using two fitting parameters, K 2 and e, which were extracted from experimentally measured maximum attenuation values A m and correspondent values of sheet resistivity R m s using Eqs. (2) and (3). For the case shown in Fig.…”

“…One can see that our values are consistent with the re- sults reported in Refs. [1,2]. The K 2 value grows with increasing the layerthickness-acoustic-wavelength ratio, as more acoustic energy becomes confined in the piezoelectric layer.…”

Surface acoustic waves in semi-insulating Fe-doped GaN films grown by hydride vapor phase epitaxy

“…[1][2][3][4][5] So far, many works have been done focusing on the fundamental properties of SAW in GaN films, including the propagation properties, the dispersion of SAW velocities, and the electromechanical coupling coefficients. [6][7][8][9][10][11][12][13] In these studies, the thickness and the resistivity of the GaN films were assumed to be key factors to affect the surface acoustic modes and the electromechanical coupling coefficients. 9,10,[14][15][16] The emergence of various acoustic modes is dependent on the ratio between the GaN film thickness and the SAW wavelength.…”