Metastable defect complexes in GaAs

We have studied the As-vacancy–Si-impurity and the As-vacancy–As-antisite complexes in GaAs using state-of-the-art electronic structure methods. The complexes show metastability as a function of the position of the impurity or the antisite atom similarly to the large-lattice relaxation models for the isolated DX and EL2 centers. Our findings suggest the enlargement of the family of metastable defects in GaAs, and the results enlighten the metastability mechanisms in the large-lattice relaxation model. In order to discuss the possible experimental detection of this type of metastability, we calculate the positron states and annihilation characteristics for the defect complexes.