Further investigations of the deep double donor magnesium in silicon

Abstract

The deep double donor levels of substitutional chalcogen impurities in silicon have unique optical properties which may enable a spin/photonic quantum technology. The interstitial magnesium impurity (${\mathrm{Mg}}_{i}$) in silicon is also a deep double donor but has not yet been studied in the same detail as have the chalcogens. In this paper, we look at the neutral and singly ionized ${\mathrm{Mg}}_{i}$ absorption spectra in natural silicon and isotopically enriched 28-silicon in more detail. The $1\mathrm{s}({\mathrm{A}}_{1}$) to $1\mathrm{s}({\mathrm{T}}_{2}$) transitions, which are very strong for the chalcogens and are central to the proposed spin/photonic quantum technology, could not be detected. We observe the presence of another double donor (${\mathrm{Mg}}_{i*}$) that may result from ${\mathrm{Mg}}_{i}$ in a reduced symmetry configuration, most likely due to complexing with another impurity. The neutral species of ${\mathrm{Mg}}_{i*}$ reveal unusual low-lying ground state levels detected through temperature dependence studies. We also observe a shallow donor which we identify as a magnesium-boron pair.