Elastic constants of GaN grown by the oxide vapor phase epitaxy method

Oxide vapor phase epitaxy (OVPE) has attracted much attention as a highly efficient method for synthesizing high-quality bulk GaN crystals, but the mechanical properties of OVPE GaN have not been clarified. We measured the five independent elastic constants of the OVPE GaN by resonant ultrasound spectroscopy. The in-plane Young modulus E _1 and shear modulus C _66 of the OVPE GaN are smaller than those of the hydride vapor phase epitaxy GaN by 1.8% and 1.3%, respectively. These reductions agree with predictions by density functional theory calculations. We also calculated the Debye temperature, revealing that oxygen impurity decreases its magnitude.