Deep levels were found in n-type material which had been annealed in N and quenched to room temperature. The energy levels and capture cross-sections of the deep levels were estimated to be about Ec - 0.42eV, and of the order of 10-17/cm2, respectively. The charge state of the deep levels was deduced to be of acceptor-type by measuring the temperature dependence of the Schottky junction capacitance. The depth profile of the deep-level density was found to correspond to that of the complementary error function, and the diffusion coefficient that was estimated from the profile was in good agreement with that of N. It was assumed that the generation of deep levels was due to the formation of N-vacancy complexes. Quenching to room temperature, and several hours of storage after quenching, were required in order to form deep levels. An attempt was made to control the deep-level density by changing the vacancy concentration. It was recalled that oxidation of the specimen surface, and the formation of O precipitates, were known to decrease the vacancy concentration since they supplied excess interstitials from the oxide and Si interfaces. The experimental results showed clearly that the deep-level density in these specimens was very low.

N.Fuma, K.Tashiro, K.Kakumoto, Y.Takano: Japanese Journal of Applied Physics, 1996, 35[1-4A], 1993-9