A series of fundamental properties from atomic geometry, electronic band structure, optical absorption, to dynamics were systemically studied for silicon doped with supersaturated chalcogens (S, Se and Te). The atomic structures in a broad energy range were obtained and distinguished as three classes named substitutional, interstitial and quasi-substitutional. Their relative energies varying with the S, Se and Te samples revealed that the concentration of impurity atoms occupying the substitutional position, which played an important role in optical absorption, will be different and get progressively higher from S-, Se- to Te-hyperdoped silicon. Electronic band structures showed that for the most atomic geometries the defect-related states did appear in the gap of silicon, and the optical absorption calculations clarified that they were the very origin of the broadband absorption of chalcogen-hyperdoped silicon. Combining the optical absorption properties with the structural transformation from molecular-dynamics simulations, the micromechanism of annealing-induced reduction of infra-red absorption was revealed. Furthermore, it was concluded that both the different concentrations of the substitutional doping and structural transformation will lead to the different annealing-induced reduction of infra-red absorption for S-, Se-, and Te-hyperdoped silicon as observed in experiments.

Physical Mechanisms for the Unique Optical Properties of Chalcogen-Hyperdoped Silicon. H.Shao, Y.Li, J.Zhang, B.Y.Ning, W.Zhang, X.J.Ning, L.Zhao, J.Zhuang: EPL, 2012, 99[4], 46005