With the evolution of epitaxial Gallium nitride (GaN) layers over a period, it expanded its wings from high-electron-mobility transistors (HEMT) to micro-electro-mechanical system (MEMS) based devices. The properties of the epitaxial layer greatly influence the performance of the HEMT and MEMS devices. This paper discusses hetero-epitaxial growth, structural and mechanical characterisation of GaN layers on three different substrates (SiC, sapphire, and Si (111)) for MEMS resonator application. The crystalline quality of the epitaxial films is evaluated by X-ray rocking curve measurements along the (0002) and (10−11) planes. The GaN/ SiC exhibited reduced screw dislocation density ∼1.28 × 107 cm−2 and edge dislocation density∼1.24 × 109 cm−2 compared to the other two epitaxial layers. The reciprocal space map (RSM) of the samples revealed the presence of in-plane compressive stress and out-of-plane tensile stress in the GaN/SiC and GaN/sapphire samples, while GaN/Si (111) sample has in-plane tensile and out-of-plane compressive stress components. The nanoindentation testing of the epitaxial layers showed an increased elastic modulus by 11.2–19 % and the hardness decreased by 2.5–23 % from their theoretical values. The effect of generated stress components coupled with the modified elastic modulus and hardness on the modal pattern and resonant frequencies of the designed GaN-based butterfly-type resonator structure has been studied. Shift in the resonant frequency (5.5 – 9.1 %) as well as the modal patterns is observed in the designed butterfly resonator. The impact of in-plane and out-of-plane stress has also been studied in the form of unique pattern formation on the wings of the designed MEMS butterfly structure.
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