Trap-assisted nonradiative recombination at Cr impurities in GaN

Chromium (Cr) impurities in GaN introduce deep-level defect states within the band gap, which may enable carrier nonradiative recombination channels that limit the performance of optoelectronic devices. Employing a comprehensive first-principles methodology, we investigate the complex carrier-capture dynamics arising from Cr, which are enhanced by its partially occupied d-orbitals. These orbitals give rise to excited states, opening an efficient internal channel for nonradiative recombination of carriers. In addition, we show that trap-assisted Auger-Meitner processes play a key role in recombination. Our calculations allow us to quantify the impact of Cr on the internal quantum efficiency of GaN-based light-emitting diodes. More generally, this work provides a theoretical framework for understanding and potentially mitigating carrier loss caused by transition-metal contaminants in wide-band-gap semiconductors.