Effect of cyclic indentation on epitaxial GaN films

Abstract

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.