Electron paramagnetic resonance and photoluminescence study of Er-impuritycomplexes in Si

Electron paramagnetic resonance (EPR) and photoluminescence (PL) spectrosco py 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 a morphous 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 degree s C for 30 s (treatment C) or treatment B+900 degrees C for 30 min (treatme nt D). Samples coimplanted to have 3 x 10(19) O/cm(3) and subject to treatm ent C show a broad line anisotropic EPR spectrum. These samples have the mo st intense low-temperature PL spectrum containing several sharp peaks attri buted to Er3+ in sites with predominantly cubic T-d symmetry. Increasing th e O concentration to 10(20)/cm(3) produces sharp line EPR spectra the stron gest of which are attributed to two Er3+ centers having monoclinic C-1h and trigonal symmetry. The principal g values and tilt angle for the monoclini c 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-tempera ture PL spectrum from this sample showed additional sharp lines but the tot al 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 a re 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 sp ecific anneal treatment but even after treatment D, Er-related PL is still observed. Samples containing 10(20) F/cm(3) and annealed with either treatm ent B or C produced an EPR spectrum attributed to Er3+ in a site of monocli nic C-1h symmetry with g(1)=1.36, g(2)=9.65, g(3)=7.91, and tau=79.1 degree s Tentative models for the structures of Er-impurity complexes are presente d and the relationship between the EPR-active and PL-active centers is disc ussed. [S0163-1829(99)04503-8].