Extraction of plasticity parameters of GaN with high temperature, in situ micro-compression

Micro-pillar compression has been utilised in a novel elevated temperature technique, in situ   in the SEM to characterise the plasticity of gallium nitride (GaN) {0001}-oriented euhedral prisms grown by metallorganic vapor phase epitaxy. Electron backscatter diffraction was used to confirm the orientation of the prisms, and deformation was observed to occur via 2nd order pyramidal slip on the {112¯2}〈112¯3〉 slip system. Analysis of the micro-compression data allowed extraction of fundamental deformation parameters of GaN from 24.5 to 479.3 °C. The strain rate sensitivity parameter was determined to be 0.0234 ± 0.0073 both by constant strain rate micro-compressions and micro-compression strain rate jump tests. The measured activation volume was 3.88 ± 0.13 × 10−29 m3, and the activation energy was 0.9 ± 0.2 eV.

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► In situ micro-compression of GaN prisms at ∼500 °C with thermal drift <0.1 nm/s.
► Direct observation of slip on the 2nd order pyramidal system during testing.
► Strain rate sensitivities from both constant rate and rate jump tests show good agreement.
► Direct extraction of crystal plasticity parameters for a specific slip system.