The mechanical strength of bulk single-crystal wurtzite-type material grown by the hydride vapor phase epitaxy technique was investigated at high temperatures by means of compressive deformation. The yield stress of GaN at 900 to 1000C was around 100 to 200Mpa; similar to that of 6H-SiC and much higher than that of Si or GaAs. From the temperature dependence of the yield stress, the activation energy for dislocation motion in GaN was estimated to be 2 to 2.7eV.

Yield Strength and Dislocation Mobility in Plastically Deformed Bulk Single-Crystal GaN. I.Yonenaga, K.Motoki: Journal of Applied Physics, 2001, 90[12], 6539-41