From dopant diffusion to optical functionality: A computational study of hyperdoped silicon

A comprehensive first-principles investigation of chalcogen-hyperdoped silicon is presented, focusing on the microscopic mechanisms driving the insulator-to-metal transition (IMT) and the associated infrared (IR) optical response. Using density functional theory and many-body perturbation theory, the formation energies and statistical probabilities of dopant complexes formed during rapid thermal annealing are analyzed. The dopant diffusion length 𝛬𝑑 is shown to critically influence the distribution of defect types and the IMT threshold concentration 𝑥𝑐 . In particular, for small diffusion lengths, chalcogen monomers dominate the defect landscape near the IMT, giving rise to distinct IR absorption features. Quasiparticle corrections and dielectric functions are computed for Si:Se and Si:Te, revealing absorption peaks in the short- and mid-wavelength IR regions. These results provide insight into the interplay between defect chemistry and optical properties in hyperdoped semiconductors, with implications for infrared photodetectors and intermediate-band photovoltaics.