Deep level generation in nitrogen-doped float-zoned silicon

In nitrogen-doped Float-Zone (FZ) silicon, nitrogen does not show any electrical activity in as-grown state. However, deep centers are known to emerge after annealing at relatively high temperatures like 900 or 1000 °C. In the present work it was found that in FZ samples of relatively high initial resistivity (greater than 1000 Ω cm, p- and n- type) the generation of deep centers is well pronounced after annealing at a lower temperature (680 °C). In p-type samples, deep donors with an energy level above the midgap are produced and the material is converted into n-type of an extremely high-resistivity. In n-type samples, deep acceptors (with an energy level also above the midgap) are generated. The deep center concentration is on the order of 1013 cm−3. A possible origin of the deep centers is interaction of a fast-diffusing interstitial nitrogen species with other impurity centers.