Nitrogen in silicon: Diffusion at 500–750 °C and interaction with dislocations

The results of dislocation unlocking experiments using nitrogen-doped float-zone silicon are reported. Dislocation unlocking stress is measured in specimens subjected to anneals for a range of durations and temperatures. Analysis of the rate of the initial rise in unlocking stress with annealing time gives an activation energy for nitrogen diffusion of 3.24 eV in the 500–750 °C temperature range. Numerical simulations of nitrogen diffusion to the dislocation core allow an approximate value of 200,000 cm2 s−1 to be estimated for the diffusivity pre-factor. These diffusion measurements are consistent with the results of higher temperature secondary ion mass spectrometry out-diffusion experiments in the literature. Other measurements made at up to 1050 °C followed by fast quenching indicate that nitrogen’s ability to lock dislocations is substantially reduced at high temperatures.