Fermi-Level Reduction Drives Vacancy-Mediated Dislocation Motion.

Dislocation motion, as a fundamental phenomenon modulating the microstructures of solid crystals, substantially affects material properties. Normally, dislocation motion is activated due to the presence of mechanical factors. But for nonmetals, nonmechanical factors like electronic stimulus have increasingly attracted interest in their potential for manipulating dislocation behavior. In this Letter, we report a forward-and-backward local core motion manner of a mixed-type partial dislocation in semiconductor aluminum nitride triggered by electron beam radiation. Such a motion behavior is beyond conventional understanding from the mechanical perspective but can be rationalized by a Fermi-level-dominated mechanism. Crystallographic analysis reveals that this local core motion is implemented by the vacancy-assisted climb of the edge component coupled with the glide of the screw component. First-principles calculations suggest that radiation-induced Fermi-level reduction modifies the charge state of dislocation cores and vacancies. Consequently, the partial dislocation core can locally move via absorbing or releasing charged vacancies to reach a lower-energy charge state. This mechanism was validated under varying irradiation conditions and is applicable to gallium nitride with a smaller band gap. Our findings identify Fermi levels as a nonmechanical stimulus of local dislocation-core motion and enrich the possible methods for dislocation manipulation in semiconductors.