Influence of hydrostatic pressure on cation vacancies in GaN, AlN, and GaAs

The effects of hydrostatic pressure on the formation energy and electronic level positions of cation vacancies in GaN, AlN, and GaAs are examined by means of ab initio calculations using a supercell approach in connection with the full-potential linear-muffin-tin-orbital method. Atomic relaxations are fully taken into account. Substantial differences are revealed in the pressure behavior of the defect level positions and formation energies for the cation vacancies in the nitride compounds and in GaAs. Additionally, the arsenic antisite in GaAs is examined, also exhibiting pressure response different from that of the vacancies. The pressure effect is strong for the vacancy and the antisite in GaAs, but for similar defects in the III-V nitrides it is rather weak.