Electrical properties of Bi-implanted amorphous chalcogenide films

The impact of Bi implantation on the conductivity and the thermopower of GeTe, Ge-Sb-Te, and Ga- La-S films is investigated. The enhanced conductivity appears to be notably sensitive to a dose of an implant. Incorporation of Bi in amorphous chalcogenide films at doses up to 1x1015 cm-2 is seen not to change the majority carrier type and activation energy for the conduction process. Higher implantation doses may reverse the majority carrier type in the studied films. Electron conductivity was observed in GeTe films implanted with Bi at a dose of 2x1016 cm-2. These studies indicate that native coordination defects present in amorphous chalcogenide semiconductors can be deactivated by means of ion implantation. A substantial density of implantation-induced traps in the studied films and their interfaces with silicon is inferred from analysis of the space-charge limited current and capacitance-voltage characteristics taken on Au/amorphous chalcogenide/Si structures.