Mechanical properties characterization of c-plane (0001) and m-plane (10-10) GaN by nanoindentation examination

The mechanical properties of m-plane (10-10) GaN single crystal was measured by nanoindentation examination for the first time. Young's modulus, Berkovich hardness and conical hardness were 284.2 GPa, 15.0 GPa and 15.7 GPa for m-plane GaN respectively. In contrast, those values in c-plane (0001) GaN were higher such as 323.8 GPa, 20.0 GPa and 21.2 GPa, respectively. Cathodoluminescence observed dislocation density distribution on m-plane GaN surface which was gradually decreased following the direction from -c axis edge to +c axis edge. By analyzing the correlation between dislocation density distribution and yield shear stress, we derived a relational equation that reprised the inverse Hall-Petch relation. This study suggested the possibility for evaluating the reliability for GaN based light emitting device by nanoindentation technique. [GRAPHICS] The typical P-h data obtained by nanoindentation in the m-plane GaN crystal performed with the conical indenter. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim