Mechanical response of GaN film and micropillar under nanoindentation and microcompression

The mechanical properties of GaN are examined by microcompression. The Young's modulus and compressive yield stress in microscale are directly measured to be similar to 226 and 10 GPa, comparable to the modulus (similar to 272 GPa) and hardness (15 GPa) measured by nanoindentation. The Raman spectrum measurements and transmission electron microscopy observations reveal that the residual stress in deposited film can be largely released in the form of micropillar. Upon microcompression, the strain energy is basically stored by dislocation and defect accumulation, with minimum residual stress regeneration. The small bending of the c-axis of the GaN micropillar upon compression would affect its optical performance. (C) 2010 American Institute of Physics. [doi:10.1063/1.3506498]