Luminescence of modified W-centers arising in silicon upon irradiation of the SiO2/Si system by Kr+ ions

Abstract

Possible nature of photoluminescence (PL) at 1240 nm revealed in silicon coated with a SiO2 film and then irradiated with Kr+ followed by annealing at 800 °C has been discussed. The spectral position of the PL is close to that of well-known W-centers, but their features are essentially different: the detected PL line retains at higher annealing temperatures and experiences lower thermal quenching. Such modification of properties of W-centers (three-interstitials I3) can be due to another I3 local defect environment which, in turn, depends on the irradiation conditions. The SiO2 film changes the shape of the distribution of primary defects, thereby assisting the separation of interstitials from vacancies. This reduces the concentration of vacancy complexes in the environment of I3, thereby shifting the spectral position of PL line and changing their properties. Such explanation is supported by the study of damage using transmission electron microscopy and by measuring PL spectra before and after removal of top silicon layers. A correlation between the PL intensity and the degree of structural damage at different depths is established. The important role of oxygen impurity, the concentration of which near the SiO2/Si interface increases due to the penetration of recoil atoms into silicon, is noted. The obtained results open up the way to create the relatively thermo-stable light-emitting complexes of point defects for silicon-based optoelectronics and quantum photonics.