Tin as a Vacancy Trap in Silicon at Room Temperature

Silicon samples which contain a high concentration of dispersed tin have been irradiated at 80°, 140° or 300°K with 3 MeV electrons. The interaction of defects (vacancies and interstitials) with tin was studied by infrared absorption measurements. The tin-vacancy pair was found by monitoring the release of vacancies when the pair anneals near 460°K. Vacancies released from tin are then trapped on oxygen to form the oxygen-vacancy defect which is measured by the strength of the 835 cm-1 line. Because vacancies are trapped at room temperature by tin atoms, tin aids in the separation of vacancy and interstitial associated defects in silicon. An absorption band at 935 cm-1 produced independent of the tin concentration is attributed to silicon interstitials trapped by oxygen in Si. This interstitial defect is stable to 330°K. Applications to devices are suggested.