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

TL;DR

This paper develops a comprehensive first-principles model to explain various boron-related optical, junction, and paramagnetic phenomena in 4H-SiC, resolving longstanding experimental puzzles about defect structures and behaviors.

Contribution

It introduces a unified theoretical framework that accounts for the stability, electronic activity, and paramagnetic properties of boron defects in 4H-SiC, addressing previous inconsistencies.

Findings

Identifies the origin of two distinct shallow boron defects with different axial orientations.

Reconciles conflicting models of a deeper boron center from photoluminescence and EPR data.

Provides temperature-dependent stability and electronic activity profiles of boron defects.

Abstract

Abstract 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.