Electron paramagnetic resonance and photoluminescence study of er-impurity complexes in si

Abstract

Electron paramagnetic resonance (EPR) and photoluminescence (PL) spectroscopy have been used to examine the structure and optical properties of erbium-impurity complexes formed in float-zone Si by multiple-energy implants at 77 K of Er together with either O or F. After implantation a 2-μm-thick amorphous layer was formed containing an almost uniform concentration of Er (Formula presented)and O (Formula presented) or (Formula presented) or F (Formula presented) Samples were annealed in nitrogen at 450 °C for 30 min (treatment A), treatment A+620 °C for 3 h (treatment B), treatment B+900 °C for 30 s (treatment C) or treatment B+900 °C for 30 min (treatment D). Samples coimplanted to have (Formula presented) and subject to treatment C show a broad line anisotropic EPR spectrum. These samples have the most intense low-temperature PL spectrum containing several sharp peaks attributed to (Formula presented) in sites with predominantly cubic (Formula presented) symmetry. Increasing the O concentration to (Formula presented) produces sharp line EPR spectra the strongest of which are attributed to two (Formula presented) centers having monoclinic (Formula presented) and trigonal symmetry. The principal g values and tilt angle for the monoclinic centers are (Formula presented) (Formula presented) (Formula presented) (Formula presented) (Formula presented) and (Formula presented) for the trigonal centers. The low-temperature PL spectrum from this sample showed additional sharp lines but the total intensity is reduced when compared to the sample with (Formula presented) For the sample containing (Formula presented) at least four distinct centers are observed by EPR after treatment B but after treatment D no EPR spectrum is observed. The PL spectra are also observed to change depending on the specific anneal treatment but even after treatment D, Er-related PL is still observed. Samples containing (Formula presented) and annealed with either treatment B or C produced an EPR spectrum attributed to (Formula presented)in a site of monoclinic (Formula presented) symmetry with (Formula presented) (Formula presented) (Formula presented) and (Formula presented)Tentative models for the structures of Er-impurity complexes are presented and the relationship between the EPR-active and PL-active centers is discussed. © 1999 The American Physical Society.