Carrier recombination mechanism at defects in wide band gap two-dimensional materials from first principles

Identification and design of defects in two-dimensional (2D) materials as\npromising single photon emitters (SPE) requires a deep understanding of\nunderlying carrier recombination mechanisms. Yet, the dominant mechanism of\ncarrier recombination at defects in 2D materials has not been well understood,\nand some outstanding questions remain: How do recombination processes at\ndefects differ between 2D and 3D systems? What factors determine defects in 2D\nmaterials as excellent SPE at room temperature? In order to address these\nquestions, we developed first-principles methods to accurately calculate the\nradiative and non-radiative recombination rates at defects in 2D materials,\nusing h-BN as a prototypical example. We reveal the carrier recombination\nmechanism at defects in 2D materials being mostly dominated by defect-defect\nstate recombination in contrast to defect-bulk state recombination in most 3D\nsemiconductors. In particular, we disentangle the non-radiative recombination\nmechanism into key physical quantities: zero-phonon line (ZPL) and Huang-Rhys\nfactor. At the end, we identified strain can effectively tune the\nelectron-phonon coupling at defect centers and drastically change non-radiative\nrecombination rates. Our theoretical development serves as a general platform\nfor understanding carrier recombination at defects in 2D materials, while\nproviding pathways for engineering of quantum efficiency of SPE.\n