Recovery Kinetics of Phosphorus Ion-Implanted a-Si:H

Abstract

AbstractHydrogenated amorphous silicon was implanted with phosphorus ions to a uniform concentration of 3×1020 cm-3 and defect saturation. The implants were annealed isochronally up to 400°C in the dark or under additional illumination. This illumination had no effect on recovery. The Urbach energy remains higher than that of silicon-implants. The midgap defect density anneals to ˜ 1018 cm-3, typical of gas-phase doped samples. The dark conductvity remains lower and its thermal activation energy higher than in gas-phase doped samples. We surmise that the Si-Si network absorbs some of the donor electron-induced defect density by forming strained Si-Si bonds. These strained bonds widen the band tails, and thus reduce the effective electron mobility and pin the Fermi level.