Properties of charged intrinsic di-interstitials in GaAs

Stable intrinsic di- interstitials configurations in GaAs with different stoichiometric compositions are studied by first principles total- energy calculations. For each composition, fully relaxed stable and metastable structures have been obtained at different charge states to study the stability properties in different doping conditions and calculate the thermodynamic transition states, showing that the studied structures are stable against the isolated interstitials with large binding energies. The structural and electronic properties of the different configurations are also discussed in order to determine the relevant observables and to plan for possible future experiments aimed to detect them. In this context, we have focused particularly on different Ga di- interstitials configurations showing that the most stable one can be detected by means of state of the art deep level detection techniques, whereas more sophisticated experiments are required, involving symmetry and thermal activation processes, to detect As di- interstitials. Combining the different techniques in an sort of " differential diagnosis," at least two of the three possible, stoichiometry dependent, di- interstitial configurations can be identified.