Isothermal annealing at 370 to 410C was used for the investigation of radiation enhanced formation of thermal donors in oxygen-rich FZ silicon irradiated with 7MeV helium ions. Results showed that formation of these defects was caused by hydrogen atoms which were diffusing from the anode contact. Hydrogen enhances diffusivity of interstitial oxygen and allowed it to react with radiation defects containing vacancies and oxygen to form a new type of thermal donors. Their distribution was then given by concentration profile of radiation damage and diffusion length of hydrogen atoms. This effect occurred only in oxygen-rich silicon annealed in air and was absent in oxygen–lean silicon and samples annealed in vacuum.

Influence of Radiation Defects on Formation of Thermal Donors in Silicon Irradiated with High-Energy Helium Ions. P.Hazdra, V.Komarnitskyy: Materials Science and Engineering B, 2009, 159-160, 346-9