The yield strength of GaN bulk crystals determined directly by means of compressive deformation was around 100 to 200MPa at 900 to 1000C. On the basis of the observed temperature and strain rate dependencies of yield stress, the dislocation mobility at elevated temperatures was evaluated. Deformed GaN exhibited a drastic reduction of photoluminescence intensity, suggesting that newly formed dislocations give rise to non-radiative recombination centers.

Dislocation Mobility and Photoluminescence of Plastically Deformed GaN. I.Yonenaga, S.Itoh, T.Goto: Physica B, 2003, 340-342, 484-7