SAW characteristics of GaN epitaxial films deposited on different plane sapphire substrates using MOCVD

The GaN/sapphire layered structure is a potential candidate for high frequency devices due to high acoustic velocity of sapphire. GaN films were grown on c, a, and r-plane sapphire substrates using an MOCVD system. Surface acoustic wave (SAW) propagation properties of GaN epitaxial layers on the sapphire have been theoretically and experimentally characterized. The experimental characterization of SAW propagation properties was performed with a linear array of interdigital transducer (IDT) structures. The formerly reported elastic moduli of GaN were examined using measured SAW velocity dispersion. We found PSAW (pseudo SAW) and HVPSAW (high velocity pseudo SAW) mode in GaN/Sapphire structure and these results agreed with the calculated velocities.