It was noted that the recent discovery of complicated isotope shifts of the photoluminescence 1014meV line in Cu-containing silicon indicated that existing models of Cu pairs were not able to account for the luminescence center. A new structural model was proposed. First-principles calculations showed that the most probable form of the complex was a four-membered complex that was composed of a substitutional Cu atom, associated with three neighbouring interstitial Cu atoms. The symmetry was C3v. In order to interpret the complicated splitting of the Γ4 exciton peak, the involvement of a non-totally symmetrical mode was proposed. The pattern of splitting obtained by using this model was almost in agreement with experiment. Selection rules beyond the usual treatments were necessary in order to correlate a specific exciton peak.

A New Structure of Cu Complex in Si and its Photoluminescence. K.Shirai, H.Yamaguchi, A.Yanase, H.Katayama-Yoshida: Journal of Physics - Condensed Matter, 2009, 21[6],064249