Dislocations were introduced into crystals by mechanical scratching at room temperature, and their optical properties were investigated by using cathodoluminescence techniques. Neither deformation-induced luminescence nor exciton luminescence was detected in the scratched region. This showed that a high density of non-radiative recombination centers was introduced on, or around, the dislocations. The H plasma treatment of a scratched crystal led to the appearance of so-called D1-D4 luminescence lines along the scratch. Deep-level transient spectroscopic data revealed that deep traps were introduced by scratching, and disappeared rapidly during subsequent H plasma treatments. It was concluded that H passivated the non-radiative recombination centers, but not the luminescence centers. The characteristics of the spatial distributions of D1 and D2 lines, and those of D3 and D4 lines, showed that these 2 groups of luminescence lines had different origins. Since the specimens which were used were free of metallic contaminants, the luminescence was not related to metallic impurities which were incorporated into dislocation cores. The non-radiative recombination centers which were introduced by scratching were annihilated by annealing at temperatures above 500C. The release of H from non-radiative centers in hydrogenated specimens did not take place before they were annihilated by annealing.

T.Sekiguchi, V.V.Kveder, K.Sumino: Journal of Applied Physics, 1994, 76[12], 7882-8