Electron irradiation damage in silicon containing carbon and oxygen

Abstract

Infra-red absorption bands have been measured in the range 1–25 μm for a large number of silicon samples containing oxygen and carbon impurities after various doses of irradiation at room temperature by 2 MeV electrons. Measurements have been made of the removal rates of oxygen and carbon from normal unperturbed interstitial and substitutional sites respectively, and similar results are presented for the growth of the A-centre and divacancy bands. The presence of oxygen increases the carbon removal rate as defined above and likewise the presence of carbon increases the removal rate for oxygen and leads to a large increase in the rate of formation of divacancies. It is concluded that carbon traps interstitial silicon atoms and is then itself ejected into interstitial sites in the manner previously found for group 111 impurities. The interstitial carbon appears to be mobile at room temperature and a large number of new vibrational bands have been observed. Several new bands thought to be of electronic origin and involving carbon atoms have also been detected.