Electron spin resonance of defects in silicon-on-insulator structures formed by oxygen implantation: Influence of γ irradiation

Abstract

Silicon-on-insulator structures obtained by single-step implantation of oxygen followed by high temperature annealing were studied by K-band electron spin resonance (ESR) at 4.3–31 K. The spectrum has a strong line at g=2.0059±0.0001 with a spin density of 7.1×1013 cm−2. Various features indicate that it is very similar to that characteristic of dangling Si-bonds (DBs) in a-Si but different from the ESR signal of the Pb center associated with single-crystal-Si/SiO2 interfaces. Irradiation by γ rays to a dose of 1 Mrad(Si) resulted in a 2.5-fold increase in DB density and in the appearance of a new, anisotropic signal of spin density 1.1×1012 cm−2. The latter signal is similar to that originating from a shallow donor in Si, of axial symmetry and preferentially aligned along [001]. It is tentatively assigned to an oxygen-related double donor in Si regions close to the Si/SiO2 interface and/or in the buried oxide. These donors are not generated by irradiation; rather, their ionization state is altered through band bending tuning resulting from irradiation-induced charges in the oxide.