It was found that there was a distinct correlation between the 1.47eV emission band, and the dislocation density in bulk material. The 1.47eV band intensified around high-dislocation areas (lineage structures) and at positions just on dislocation bundles. On the other hand, the 1.47eV band was hardly observed in low-dislocation areas (with etch pit densities of less than 2 x 105/cm2) or at positions away from dislocation bundles. Moreover, the 1.47eV band was intensified by gamma-irradiation of 1.7 x 107Gy; which produced a large number of Frenkel defects. It was shown that the 1.47eV band was related not only to an extended defect such as a dislocation, but also to a point defect such as a Frenkel defect. These results suggested that the strain field which was induced in the vicinity of the defects was responsible for the recombination center of the 1.47eV band.

S.Seto, A.Tanaka, F.Takeda, K.Matsuura: Journal of Crystal Growth, 1994, 138[1-4], 346-51