Electron paramagnetic resonance and photoluminescence study of Er-impurity complexes in Si

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-mu m-thick amorphous layer was formed containing an almost uniform concentration of Er (10(19)/cm(3)) and O (3 x 10(19)/cm(3) or 10(20)/cm(3)) or F (10(20)/cm(3)). Samples were annealed in nitrogen at 450 degrees C for 30 min (treatment A), treatment A+620 degrees C for 3 h (treatment B), treatment B+900 degrees C for 30 s (treatment C) or treatment B+900 degrees C for 30 min (treatment D). Samples coimplanted to have 3 x 10(19) O/cm(3) 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 Er3+ in sites with predominantly cubic T-d symmetry. Increasing the O concentration to 10(20)/cm(3) produces sharp line EPR spectra the strongest of which are attributed to two Er3+ centers having monoclinic C-1h and trigonal symmetry. The principal g values and tilt angle for the monoclinic centers are g(1)=0.80, g(2)=5.45, g(3)=12.60, tau=57.30, g(parallel to)=0.69, and g(perpendicular to)=3.24 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 3 x 10(19) O/cm(3). For the sample containing 10(20) O/cm(3) 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 10(20) F/cm(3) and annealed with either treatment B or C produced an EPR spectrum attributed to Er3+ in a site of monoclinic C-1h symmetry with g(1)=1.36, g(2)=9.65, g(3)=7.91, and tau=79.1 degrees Tentative models for the structures of Er-impurity complexes are presented and the relationship between the EPR-active and PL-active centers is discussed. [S0163-1829(99)04503-8].