Crystalline structures and defects in liquid GaN during rapid cooling processes

The formation of crystalline structures and defects in GaN at three different cooling rates were investigated based on molecular dynamics simulations by using the Stillinger-Weber potential. The structural properties of GaN during the solidification processes were analyzed by several structural analysis methods. The system formed crystals at 200 K when cooled at rates of 1011 K/s and 1012 K/s, whereas the amorphous state that formed at the cooling rate of 1013 K/s included some crystal clusters. The 〈4 0 0 0〉 and 〈2 3 0 0〉 Voronoi polyhedrons were dominant in GaN during the rapid quenching processes. The 〈4 0 0 0〉 polyhedrons can aggregate to form cubic and hexagonal phases in GaN at lower temperatures. After solidification, cubic and hexagonal structures were coexistent in the system with a hybrid disordered region and crystal defects. When the temperature was decreased at a rate of 1011 K/s, coherent twin boundaries, having excellent structural stability and configural continuity, were easily formed between the cubic and hexagonal crystal structures.