Astract: Based on the first-principles method of density functional theory, this paper aims to explore the theoretical calculation method for determining the critical concentration of insulator-metal transition. Taking Co heavily doped Si as the research object, the crystal structure, impurity formation energy and electronic properties of 10 models with different Co doping concentrations are constructed and calculated. It is found that impurity energy levels are formed in the band gap of Co doped Si system. The position and width of impurity energy level change linearly with the increase of Co concentration. When the Co doping concentration is high, the impurity formation energy is gradually stable, and the impurity energy level crosses Fermi level, which makes the system metallic. Based on the changing trend of impurity formation energy and the distance between the minimum of impurity energy level and Fermi level, it can be predicted that the Co doping concentration with insulator-metal transition is 2.601 cm^-3, which is consistent with the experimental results.

DOI：10.3969/j.issn.1000-0364.2019.02.028