The As2V complex in silicon: Band-gap levels, migration and annealing

In this study, we used n(+)p mesa diodes where the highly arsenic doped n(+) top layer was grown by molecular-beam epitaxy on top of a 5-mu m thick p-type layer grown by chemical-vapour deposition. The diodes were irradiated with 2 MeV electrons at room temperature and the resulting defects in the p-type region were studied by Laplace and standard deep-level transient spectroscopy. A new defect with an apparent energy position of 0.20 eV above the valence band is shown to migrate from the n(+) top layer into the p-type material where it is observed by DLTS. An annealing study shows that this defect grows in at similar to 400 K and disappears at similar to 460 K. We argue that this defect is the AsV complex, and that it is formed in the top layer when negatively charged AsV pairs, which are generated in the n+ top layer by the electron irradiation, migrate and react with the abundant and positively charged As donors. Once formed, the AS(2)V complex diffuses into the p-type material.