The insulator-to-metal transition of Co hyperdoped crystalline silicon

Abstract

Co hyperdoped crystalline silicon samples were prepared by the combination of ion implantation and pulsed laser melting techniques. The current–voltage curves of the heavily Co-implanted samples present a rectifying behavior, which is related to the contact between the Co implanted layer and the Si substrate. The temperature dependences of the resistances indicate that an insulator-to-metal transition probably happens in the low temperature range. The transition occurs in the Co concentration range of 3 × 1019 – 6 × 1020 cm−3, which corresponds to the Mott insulator-to-metal transition limit. The temperature dependences of the resistances are well fitted based on a simplified two-layer model consisting of an intermediate band layer and a substrate layer. The fitting intermediate band location is at about 0.51 eV below the conduction band edge of Si. The Co hyperdoped crystalline silicon is a kind of potential material for intermediate band solar cells.