Investigations of the deep double donor magnesium in silicon

Synopsis

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 in silicon is also a deep double donor but has not yet been studied in the same detail as have the chalcogens. In this study we look at the neutral and singly ionized Mg¬i absorption spectra in natural silicon and 28-silicon in more detail, looking in particular for the 1s(A1) to 1s(T2) transitions which are very strong for the chalcogens and are central to the proposed spin/photonic quantum technology. We further observe the presence of another donor (Mgi*) that may result from Mgi in a reduced symmetry configuration, due to either complexing or the occupation of an interstitial site with symmetry lower than the usual tetrahedral site. The neutral species of Mgi* reveal additional low lying ground state levels detected through temperature dependence studies. We also observe a new shallow donor which we identify as an Mg-B pair center. Additionally we present photoluminesence spectra that verify the existence of an Mg-Mg isoelectronic pair center through its isotopic fingerprint. We further include the results of a temperature dependence and photoluminesence lifetime study of this same center, revealing unusual behaviour of the main no-phonon line and associated phonon replicas.