First-principles studies of hydrogen irradiation effects on the photoluminescence properties of nitrogen-vacancy centers in 4H-SiC

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Nitrogen-vacancy (NV) color centers in 4H-SiC have gained prominence in quantum technology as room-temperature controllable near-infrared single-photon sources and quantum bits, with various ion irradiation techniques employed for their fabrication; among these methods, hydrogen (H) ion irradiation has emerged as a particularly attractive approach because of its precision and minimal lattice damage. However, the influence of H on the photoluminescence (PL) properties of NV centers remains largely unexplored. In this work, we systematically investigate the effects of H irradiations using first-principles calculations. Our results reveal the dual roles of H in 4H-SiC: on the one hand, H can passivate NV^- by inevitably forming NVHₙ complexes; on the other hand, H can form new color centers NVH^-4pt0ex(S=1/2) with significantly lower zero-phonon line (ZPL) energies than NV^-, exhibiting PLs with no overlap with those of NV^- in the range 1150--1450 nm. Our results not only reveal the underlying mechanism for the experimentally observed PL decay in NV^- ensemble prepared via hydrogen irradiation but also suggest NVH^- as a promising infrared single-photon source (SPS) in the IR-B region. We further elucidate the distinct PL characteristics of NV^- and NVH^- arising from their atomic configuration differences, providing detailed theoretical interpretations for experimental observations.