Walking the path from B4- to B1-type structures in GaN

Molecular dynamics simulations are performed on the wurtzite-type structure (B4) to the rocksalt-type structure (B1) pressure-induced phase transition in GaN. From this, a nucleation and growth mechanism through a tetragonal metastable configuration is found. An intermediate of h-MgO type structure suggested from static calculations is ruled out. However, the pathway through the tetragonal intermediate may be altered by defect incorporation. While the overall transformation mechanism is preserved for both vacancies and Ga substitution by indium, already a 5% aluminum substitution establishes a transition route which avoids the tetragonal structure. Changes in the transformation mechanism and the resulting stabilization of the previously metastable high-pressure modification is elaborated by tracing the interplay of phase nucleation and growth and defect incorporation.