Yield shear stress dependence on nanoindentation strain rate in bulk GaN crystal

The strain rate controlled nanoindentation was performed in c‐plane (0001) and m‐plane (10–10) GaN crystals. The indentation velocity was ranged from 0.16 to 800 nm/s. The significant displacement bursts were detected after every perfect elastically deformations and they allowed us to calculate the maximum shear stress τmax. The τmax dependences on strain rate in two crystal orientations involved that the two perpendicular compressions induced the same plastic deformation mechanism. Comparing the obtained τmax with the Peierls potential and maximum shear stress in each slip system, {10–11} 〈11–20〉 dislocation nucleation may support the origin of the plastic deformation in GaN crystal. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)