Cathodoluminescence rosettes in c-plane GaN films under Berkovich nanoindentation

Abstract In this study, the length of Berkovich nanoindentation-induced rosette arms revealed by cathodoluminescence (CL) spectroscopy was examined as a function of applied loading for the c-plane GaN thin films. Results indicated that a well-defined rosette structure with apparent six-fold symmetry extends from the center of indentation along the 〈 1 1 2 ¯ 0 〉 directions, suggesting that the plastic deformation is dominated by dislocation gliding on the active slip system of hexagonal GaN thin films. The length of the longest rosette arm can be satisfactorily described by the Johnson’s hemispherical hydrostatic model and gives a flow stress of ∼1.5 GPa for the c-plane GaN thin films.