Electrical and optical inhomogeneities around dislocations were studied in Si-doped liquid-encapsulated vertically grown material. The atmospheres of the dislocations were determined by using a combination of photo-etching, high-resolution photoluminescence mapping and carrier density mapping. A broad photoluminescence emission band, with a peak at 0.95eV, usually appeared in Si-doped wafers and the microscopic intensity pattern of the band corresponded with the photo-etching features. The intensity increased in the core region of the dislocations and decreased in the surrounding area. The band-edge emission exhibited a complementary intensity pattern. Carrier density mapping indicated that the carrier concentration was higher in the dislocated area, and was related to the photoluminescence intensity pattern. The results indicated that the micro-defects which were responsible for the 0.95eV band were acceptors and acted as killer centers for the band-edge emission. After solidification, they were gettered by dislocations and a denuded zone was expected to form in the surrounding region. Optical and electrical inhomogeneities then occurred around the dislocations.

R.Toba, M.Warashina, M.Tajima: Materials Science Forum, 1995, 196-201, 1785-90