A Mg-pair isoelectronic bound exciton identified by its isotopic fingerprint in $^{28}$Si

TL;DR

This study identifies a Mg-pair isoelectronic bound exciton in enriched $^{28}$Si through isotopic fingerprinting, confirming its origin and revealing complex temperature-dependent behavior.

Contribution

The paper provides the first isotopic fingerprinting of a Mg-pair bound exciton in $^{28}$Si, confirming its atomic origin and detailed spectral structure.

Findings

The no-phonon line splits into five components matching Mg isotope combinations.

Isotopic fingerprinting confirms the Mg-pair bound exciton hypothesis.

Temperature dependence shows unusual behavior not yet explained.

Abstract

We use the greatly improved optical linewidths provided by highly enriched $^{28}$Si to study a photoluminescence line near 1017 meV previously observed in the luminescence spectrum of natural Si diffused with Mg, and suggested to result from the recombination of an isoelectronic bound exciton localized at a Mg-pair center. In $^{28}$Si this no-phonon line is found to be comprised of five components whose relative intensities closely match the relative abundances of Mg-pairs formed by random combinations of the three stable isotopes of Mg, thus confirming the Mg-pair hypothesis. We further present the results of temperature dependence studies of this center that reveal unusual and as yet unexplained behaviour.