Effect of Nitrogen Doping on Microdefects and Minority Charge Carrier Lifetime of High-Purity, Dislocation-Free and Multicrystalline Silicon

We studied the effects of Si growth in atmospheres containing N2 on minority charge carrier lifetime ..tau.. using a high-purity, induction-heated, float-zone (FZ) crystal growth method. Ingots were grown with purge gases that ranged from pure argon (99.9995%) to pure N2 (99.999%). ..tau.. was measured as a function of position along with ingots using the ASTM F28-75 photoconductive decay (PCD)method. We found that Ga-doped, multicrystalline silicon ingot growth in a partial or total nitrogen ambient has a negligible effect on minority charge carrier lifetime and no significant grain boundary passivation effect. Values of 40 ..mu.. <..tau..<100..mu..s were typical regardless of ambient. For dislocation-free (DF) growth, the degradation of ..tau.. is minimal and ..tau.. values above1000 ..mu..s are obtained if the amount of N2 in the purge gas is below the level at which nitride compounds form in the melt and disrupt DF growth.