Ab initio studies of arsenic and boron related defects in silicon mesa diodes

E centers are known to diffuse around 400 K in Si and may then form larger donor-vacancy defects such as As2V in heavily doped n-type Si doped with As or AsBV if they diffuse into p-type regions. Ab initio methods are used to explore these possibilities. The AsV defect possesses electrical levels in agreement with experiments. The AsBV defect is found to exhibit a charge-dependent structure, has a barrier to dissociation of similar to 1.4 eV, and possesses an acceptor level at 0.27 or 0.47 eV above the valence band top depending on the defect structure. The As2V defect possesses only an acceptor level at 0.22 eV below the conduction band. Comparison is made with recent experiments carried out on mesa diodes. (c) 2007 American Institute of Physics.