Effect of cyclic indentation on epitaxial GaN films

This paper describes the mechanisms of Berkovich nanoindentation induced mechanical deformation of GaN films under various loading–reloading cycles, analysed using cathodoluminescence, atomic force microscopy (AFM) and SEM. The AFM and SEM studies revealed that bursts, due to the nucleation of dislocations, occurred after nine loading–reloading cycles; these bursts resulted in incipient slip bands and/or the to and fro motion of mobile dislocations under the stress field. Cathodoluminescence analysis indicated the generation of individual dislocations and residual deformation on the GaN film; the decrease in hardness H can be used to determine the material properties of films undergoing repeated loading–reloading cycles.