Theory of shallow and deep boron defects in 4H-SiC

Despite advances toward improving the quality of p-type 4H-SiC substrates and layers, we still have no model capable of accounting for the multitude of boron-related optical, junction, and paramagnetic resonance experiments available in the literature. A conspicuous puzzle is the observation of two shallow boron defects with rather distinct axial orientations as found by electron paramagnetic resonance (EPR) and electron nuclear double resonance (ENDOR) data. This feature is not observed in material doped with other group-III elements. Another open issue involves conflicting conclusions from photoluminescence and EPR studies of a deeper boron center, which has been linked to rather distinct models, either based on substitutional or vacancy-related boron defects. We unlock these and other problems by means of first-principles calculations, where the temperature-dependent stability, the electronic activity, and the paramagnetic response of boron defects in 4H-SiC are investigated.

Automated summary

Despite the numerous boron-related experiments, there is still no model that can explain them. One puzzle is the observation of two shallow boron defects with distinct axial orientations, which are not found in materials doped with other group-III elements. Additionally, conflicting conclusions have been drawn from photoluminescence and EPR studies of a deeper boron center, which are associated with different models based on substitutional or vacancy-related boron defects. By using first-principles calculations, we address these and other issues.