Interaction of dislocations with impurities in silicon crystals studied byin situX-ray topography

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Abstract
The characteristics of dislocation locking due to the development of an impurity atmosphere have been investigated by the in situ X-ray topographic technique for silicon crystals doped with various types of impurities. Oxygen, nitrogen and phosphorus atoms are found to be effective in locking dislocations while carbon atoms are not. The dependence of the locking behaviour on the impurity concentration is investigated in detail for oxygen-doped crystals. It is known that the magnitude of the locking force is determined uniquely by the number of impurity atoms congregated on a unit length of dislocations if the species and concentration of the impurity atoms in the crystal are specified. Individual nitrogen atoms exhibit the strongest locking effect among the impurity atoms investigated. However, locking proceeds most pronouncedly in oxygen-doped crystals owing to a high diffusion rate and a higher solubility of oxygen atoms in silicon. The origins of the strong locking effects of various impurity atoms are discussed.