An IR Study of the Annealing behaviour of A-Center in Silicon

摘要

The current understanding of the vacancy-oxygen (VO) pair, the so-called A-center in silicon is more than satisfactory. However, the annealing behaviour of the center exhibits some features which need proper explanation in order that the whole picture for the defect becomes more clear. To this end, we investigated the evolution of the infrared signal of the center (828cm~(-1) LVM band) created in Cz-grown Si by neutron irradiation, as a function of the heat treatment. The amplitude of the band appears to be stably up to 200 deg C where it begins to increase reaching a maximum value at approx280 deg C and then begins to decrease rapidly up to approx 400 deg C, although a small portion of it lingers in teh spectra up to 550 deg C. The inverse annealing stage (200-280 deg C), the mechanisms and the annealing kinetics of the defect as it decay out (300-400 deg C) and the stabilization of the defect signal (400-500 deg C) are the main points which concern the present investigation. After completign the annealing sequence and re-irradiating the material, the inverse annealing stage is asent. This led us to surmise the presence of an unknown defect (X-defect) which compete with O_i in capturing vacancies. The stabilization of the 828cm~(-1) band amplitude above 400 deg C has been tentiatively ascribed to the trapping of a number of A-centers near disordered regions or large defects. This fact results to a larger binding energy of the corresponding defects.