This paper aims to review the consistency of existing GaN stiffness data and measure the high temperature elastic moduli of free-standing (0001) GaN. Dynamic mechanical thermal analysis (DMTA) and impact excitation were used to determine the E33 elastic modulus at room temperature and at temperatures up to 550°C. At room temperature, E33 ranged from 304 GPa to 279 GPa depending on the specific sample and measurement method. Using DMTA and a calibration with silicon, the elastic modulus decreased by 2.17% between 100°C and 500°C, in close agreement with the literature. By testing samples cut at a range of crystal orientations the isotropy of the stiffness in the (0001) plane was confirmed.
Hicks, M., Tabeart, J., Edwards, M. J., Le Boulbar, E. D., Allsopp, D. W. E., Bowen, C. R., & Dent, A. C. E. (2012). High temperature measurement of elastic moduli of (0001) gallium nitride. Integrated Ferroelectrics, 133(1), 17-24. https://doi.org/10.1080/10584587.2012.663309