The behavior of oxygen and nitrogen impurities in silicon has been investigated using a novel dislocation locking technique. The locking effect of oxygen in Czochralski silicon (CZ-Si) was investigated in the 350-850° C temperature range and was found to display five well-defined regimes as a function of annealing time. Results indicate that enhanced transport of oxygen to dislocations takes place for temperatures below ∼ 700° C. Numerical simulations of the enhanced oxygen transport indicate that the effective diffusivity becomes dependent on oxygen concentration with an activation energy of approximately 1.5 eV. The same technique has been used to investigate nitrogen transport in nitrogen-doped float-zone silicon in the 550-830° C temperature range and shows nitrogen to have a comparable locking effect to oxygen in CZ- Si, despite being present in a concentration that is 2 orders of magnitude lower. The stress required to unlock dislocations at 550° C which have previously been immobilized by nitrogen during an annealing step, initially increases approximately linearly with the duration of the anneal before saturating to a steady-state value of approximately 50 MPa for all anneal temperatures investigated. An expression for the transport of nitrogen to the dislocations was deduced, which has an activation energy of 1.45 eV. © 2005 The Electrochemical Society. All rights reserved.