Shallow thermal donors in nitrogen-doped silicon

Silicon crystals doped with nitrogen from the melt contain shallow thermal donors (STDs) detected both optically and electrically. Annealing samples at 600 and 650 °C results in a saturated STD concentration that depends on the nitrogen concentration approximately by a square-root law. This indicates the involvement of only one nitrogen atom in every STD species. The model of STDs consistent with the present data is the NOm complex of a nitrogen interstitial and m oxygen atoms; the concentration of every STD species reaches the equilibrium value during annealing. The temperature dependence of the equilibrium reaction constant allows us to estimate the average number of oxygen atoms m of the STD complexes as 3.