Physical mechanisms for the unique optical properties of chalcogen-hyperdoped silicon

¹ Shanghai Ultra-Precision Optical Manufacturing Engineering Center, Department of Optical Science and Engineering, Fudan University - Shanghai 200433, China
² State Key Laboratory of Surface Physics and Department of Physics, Fudan University - Shanghai 200433, China
³ Applied Ion Beam Physics Laboratory, Institute of Modern Physics, Department of Nuclear Science and Technology, Fudan University - Shanghai 200433, China

^(a) lizhao@fudan.edu.cn
^(b) junzhuang@fudan.edu.cn

Received: 1 June 2012
Accepted: 26 July 2012

Abstract

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