Electronic and structural properties of grain boundaries in electron-irradiated edge-defined film-fed growth silicon

Edge-defined film-fed growth (EFG) is an economical method of producing multicrystalline silicon ribbon for solar cells. Such silicon is heavily doped with carbon. After electron irradiation, the dominant defect found in this material is the G centre, which is associated with the CsCi defect. In this paper, the techniques of scanning cathodoluminescence and electron backscattered diffraction pattern analysis are used to correlate the luminescence from the G centre with the grain boundary structure in electron-irradiated EFG silicon. A localised enhancement of G centre luminescence is found near twin boundaries at temperatures above 20K, whereas no such enhancement is found near low angle grain boundaries at temperatures up to 80K or at twin boundaries below 20K. This behaviour may be caused by thermal ionisation of excitons from traps at the twin boundaries, and their subsequent capture at G centres.