Nanoindentation-Induced Pop-In Effects in GaN Thin Films

The nanoindentation-induced pop-in phenomena in GaN thin film are investigated using Berkovich indenters. The formation of dislocation rosettes revealed by cathodoluminescence (CL) spectroscopy is found to closely relate with the pop-in effect displayed in depth-sensitive measurements. Namely, the CL images of the indented spots show well-defined rosette structures consistent with the hexagonal symmetry of GaN, indicating that the distribution of deformation-induced extended defects/dislocations may dramatically affect the CL emission. The use of CL thus may provide an alternative means for studying the near-surface plasticity in other semiconductor thin films, as well.