Optical Properties of the Niobium Centre in 4H, 6H, and 15R SiC

Abstract

A set of lines in the photoluminescence spectra of 4H-, 6H-, and 15R-SiC in the near-infrared are attributed to Nb-related defects on the ground of doping experiments conducted with 4H-SiC. A model based on a an exciton bound at the Nb-centre in an asymmetric split vacancy configuration at a hexagonal site is proposed, which explains the structure of the luminescence spectrum and the observed Zeeman splitting of the lines.

Optical properties and Zeeman spectroscopy of niobium in silicon carbide

“…The mechanism of binding an exciton to Nb can be considered also from another point of view, as is done in Ref. [18] and outlined briefly here. The five valence electrons of the Nb atom are used to saturate five of the six dangling bonds of the divacancy (three from the silicon vacancy, and three from the carbon vacancy; cf.…”

“…(Some data is adapted with permission from Ref. [18].) that, to the best of our knowledge, this line is not among the commonly detected lines in as-grown samples [14].…”

“…[18], the PL lines due to Nb in the ASV h-h configuration are actually arising from recombination of an exciton bound to the defect. The main idea-a bound exciton consisting of a tightly bound electron and Coulombically bound hole-is corroborated here by a semiquantitative estimate of the exciton recombination energy obtained within a simple physical picture using previously calculated energies [16] of the Nb defect in different charge states.…”

“…(A preliminary account on some of the experimental data and the model was presented in [18]). We consider also the Zeeman splitting of the Nb-related lines on the grounds of phenomenological models and compare the experimental line splitting with the predictions of these models.…”