A new structure of Cu complex in Si and its photoluminescence

Abstract

A recent discovery of complicated isotope shifts of the PL 1014 meV line in Cu-containing silicon, which was made by Thewalt's group, indicates that existing models of Cu pairs are not appropriate for accounting for the luminescence center. A new structural model has been studied. First-principles calculations show that the most probable form of the complex is a four-membered complex which is composed of a substitutional Cu associated with three neighboring interstitial Cu atoms. The symmetry is C(3v). The formation mechanism of this complex is discussed. For interpreting the complicated splitting for the Γ(4) exciton peak, involvement of a non-totally symmetric mode is proposed. The pattern of splitting obtained by this model is almost in agreement with the experiment. Selection rules beyond the usual treatments are necessary to connect a specific exciton peak to the corresponding phonon.

Cu complex in silicon and its photoluminescence

“…The local symmetry of the complex is C 3v , which is consistent with the uniaxial stress experiment by Weber et al [2]. The further additional subpeak structures found for Γ 4 line are interpreted in terms of non-totally symmetric phonon mode of this complex, probably an E mode [9].…”

“…To study this PL center, we have investigated the stable configuration of Cu complex by first-principles calculation [9]. It is shown that a fourmembered complex Cu (s) Cu (3i) is the most stable configuration; one substitutional Cu and three neighboring interstitial Cu's.…”

“…In our previous study [9], only general properties of symmetry of phonons were used to study the Γ 4 splitting. Although phonon frequency was calculated by a model in order to illustrate splitting, no attempt to check the correctness of frequency was made.…”

“…The used code is "Osaka2k". The details of self-consistent calculations are described in our previous study [9]. A Cu (s) Cu (3i) complex is embedded in 64-atom supercell without any symmetry constraints.…”

Accelerated light-induced degradation for detecting copper contamination in p-type silicon

“…Recombination-free four-copper-atom complexes start dissociating at 150 C 24 releasing three Cu i þ ions and an unknown Cu DLA center, 25 which might be Cu s . 26,27 Nevertheless, as substitutional copper is recombination active, 2 any Cu s release would cause a lifetime decrease at 200 C instead of the observed lifetime increase. Correspondingly, any other Cu s formation at 200 C would cause a further lifetime decrease, such as Cu i þ reaction with a vacancy, 28 a silicon self-interstitial, 29 or an oxygenvacancy center.…”