The photoluminescence of Er-doped semi-insulating polycrystalline or amorphous material which contained 30at%O was studied. The films were deposited onto monocrystalline Si substrates by means of chemical vapor deposition, implanted with 500keV Er ions to fluences which ranged from 5 x 1013 to 6 x 1015/cm2, and annealed at between 300 and 1000C. When optically pumped at near to 500nm, the samples exhibited a room-temperature luminescence, at around 1.54, which was due to intra-4f transitions in Er3+; excited by photo-generated carriers. The strongest luminescence was observed after annealing at 400C. Two classes of Er3+ could be distinguished, and were characterized by luminescence lifetimes of 170 or 800s. The classes were attributed to Er3+ in Si-rich or O-rich environments. Photoluminescence excitation spectroscopic studies of a sample with 1015Er/cm2 showed that about 2% of the implanted Er was optically active. No quenching of the Er luminescence efficiency was observed between 77K and room temperature. The internal quantum efficiency for the excitation of Er3+, via photo-generated carriers, was equal to 0.001 at room temperature. The luminescence was explained in terms of the trapping of carriers at localized Er-related defects, and subsequent energy transfer to Er3+ ions which then decayed by emitting 1.5 photons.

G.N.Van den Hoven, J.H.Shin, A.Polman, S.Lombardo, S.U.Campisano: Journal of Applied Physics, 1995, 78[4], 2642-50