Temperature dependence of the AB lines and optical properties of the carbon–antisite-vacancy pair in 4H−SiC

Defects in semiconductors have in recent years been revealed to have interesting properties in the venture towards quantum technologies. In this regard, silicon carbide has shown great promise as a host for quantum defects. In particular, the ultrabright AB photoluminescence lines in <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><a:mn>4</a:mn><a:mi>H</a:mi><a:mtext>−</a:mtext><a:mi>Si</a:mi><a:mi mathvariant="normal">C</a:mi></a:math> are observable at room temperature and have been proposed as a single-photon quantum emitter. These lines have previously been studied and assigned to the carbon–antisite-vacancy (CAV) pair. In this paper, we report on new measurements of the AB lines’ temperature dependence, and carry out an in-depth computational study on the optical properties of the CAV defect. We find that the CAV defect has the potential to exhibit several different zero-phonon luminescences with emissions in the near-infrared telecom band, in its neutral and positive charge states. However, our measurements show that the AB lines only consist of three nonthermally activated lines instead of the previously reported four lines; meanwhile, our calculations on the CAV defect are unable to find optical transitions in full agreement with the AB-line assignment. In light of our results, the identification of AB lines and the associated room-temperature emission require further study.