Metallic conduction behavior in selenium-hyperdoped silicon

Hall measurements at 80-300 K are performed on crystalline silicon doped with selenium exceeding the equilibrium solid solubility limit using ion implantation combined with furnace annealing. The temperature dependence of free carrier density and sheet conductivity of the Se doping layer changes with implantation dose. Metallic conduction behavior is well observed in the sample doped with selenium to be 7.4×1020/cm3. The overlapping between Se impurity states below Si conduction band might give a microscopic explanation.