First-principles theory of copper in silicon

The properties of copper in silicon calculated from first-principles methods are reviewed and discussed. The defects studied so far include interstitial and substitutional copper, Cu complexes with the vacancy and vacancy clusters, Cuself-interstitial pairs, Cu-shallow acceptor pairs, Cu-H, and Cu-O interactions, and Cu-Cu pairs. The variety of these interactions is possible because the 3d shell of Cu is full only for the free atom. Inside the Si matrix, some electrons are promoted from the 3d shell into the 4sp shell, and copper easily forms multiple (weak but) covalent bonds, in particular with native defects and impurities such as H. However, the interactions between interstitial Cu and interstitial O or the A-center do not involve the formation of a Cu-O bond, as oxygen much prefers to bind to silicon.