Luminescence from erbium-doped silicon nanocrystals in silica: Excitation mechanisms (original) (raw)
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Physics of the Solid State, 2005
The photoluminescence (PL) spectra and kinetics of erbium-doped layers of silicon nanocrystals dispersed in a silicon dioxide matrix (nc-Si/SiO 2) are studied. It was found that optical excitation of nc-Si can be transferred with a high efficiency to Er 3+ ions present in the surrounding oxide. The efficiency of energy transfer increases with increasing pumping photon energy and intensity. The process of Er 3+ excitation is shown to compete successfully with nonradiative recombination in the nc-Si/SiO 2 structures. The Er 3+ PL lifetime was found to decrease under intense optical pumping, which implies the establishment of inverse population in the Er 3+ system. The results obtained demonstrate the very high potential of erbium-doped nc-Si/SiO 2 structures when used as active media for optical amplifiers and light-emitting devices operating at a wavelength of 1.5 µ m.
Excitation mechanism of erbium photoluminescence in bulk silicon and silicon nanostructures
Materials Science and Engineering: B, 2003
We present a short review of the theoretical and experimental results concerning the problem of excitation mechanism of erbium photoluminescence in silicon and silicon nanostructures. The excitation process consists of two stages, the first being absorption of radiation by bulk silicon matrix or nanocrystals while the second is the Auger excitation of erbium ions by recombining electron-hole pairs. The large values of Auger excitation cross-section under optical pumping in semiconductor matrices are due to large values of band-to-band absorption coefficient of bulk silicon or silicon nanocrystals exceeding by several orders of magnitude the absorption coefficient of erbium in dielectric SiO 2 matrix. The specific features of Auger process in silicon nanocrystals when excitation of erbium ions is produced by quantum-confined electron-hole pairs are discussed.
Photoluminescence of erbium ions in heterostructures with silicon nanocrystals
Semiconductors, 2006
Photoluminescence properties of erbium-doped silicon dioxide layers containing silicon nanocrystals with 1.5-4.5 nm average size are investigated. It is found that the intensity and mean lifetime of the Er 3+-ion photoluminescence depend on the nanocrystal size, optical pump intensity, and temperature. The results obtained are explained both by the effect of the local environment on Er 3+ ions and by the manifestation of nonradiative deexcitation of ions caused by the transfer of energy back into the solid-state matrix and the Auger processes.
Applied Physics Letters, 2001
The exciton-erbium coupling and the excitation dynamics of Er 3ϩ in erbium-doped silicon-rich silicon oxide are investigated using time-resolved measurements of Er 3ϩ luminescence. The dependence of the Er 3ϩ luminescence on the pump power and duration indicates that the excitonerbium coupling is dominant over carrier-exciton coupling. The results further support the idea that the luminescent Er 3ϩ ions are not in the Si nanoclusters but in the interface region surrounding the nanoclusters.
Carrier-induced quenching processes on the erbium luminescence in silicon nanocluster devices
Physical Review B, 2006
The luminescence-quenching processes limiting quantum efficiency in Er-doped silicon nanocluster lightemitting devices are investigated and identified. It is found that carrier injection, while needed to excite Er ions through electron-hole recombination, at the same time produces an efficient nonradiative Auger deexcitation with trapped carriers. This phenomenon is studied in detail and, on the basis of its understanding, we propose device structures in which sequential injection of electrons and holes can improve quantum efficiency by avoiding Auger processes.
Rate equation modelling of erbium luminescence dynamics in erbium-doped silicon-rich-silicon-oxide
Journal of Luminescence, 2012
Erbium doped silicon-rich silica offers broad band and very efficient excitation of erbium photoluminescence (PL) due to a sensitization effect attributed to silicon nanocrystals (Si-nc), which grow during thermal treatment. PL decay lifetime measurements of sensitised Er 3 þ ions are usually reported to be stretched or multi exponential, very different to those that are directly excited, which usually show a single exponential decay component. In this paper, we report on SiO 2 thin films doped with Si-nc's and erbium. Time resolved PL measurements reveal two distinct 1.54 mm Er decay components; a fast microsecond component, and a relatively long lifetime component (10 ms). We also study the structural properties of these samples through TEM measurements, and reveal the formation of Er clusters. We propose that these Er clusters are responsible for the fast ms decay component, and we develop rate equation models that reproduce the experimental transient observations, and can explain some of the reported transient behaviour in previously published literature.
Nanoscale research letters, 2014
The structural and optical properties of erbium-doped silicon-rich silica samples containing different Si concentrations are studied. Intense photoluminescence (PL) from luminescence centers (LCs) and silicon nanoclusters (Si NCs), which evolves with annealing temperatures, is obtained. By modulating the silicon concentrations in samples, the main sensitizers of Er(3+) ions can be tuned from Si NCs to LCs. Optimum Er(3+) PL, with an enhancement of more than two, is obtained in the samples with a medium Si concentration, where the sensitization from Si NCs and LCs coexists.
On the mechanism of electroluminescence excitation in Er-doped SiO2 containing silicon nanoclusters
Optical Materials, 2005
The effect of the density of silicon nanoclusters on both electroluminescence (EL) and photoluminescence (PL) of Er 3+ ions in indium-tin oxide/SiO 2 :Er/n-type silicon metal-oxide-semiconductor structures was studied by co-implantation of excess silicon into a 200 nm SiO 2 layer with a concentration in the range of 1-15%. Contrary to the PL, the EL from both the green and infrared peaks of Er 3+ shows a dramatic quenching when the average distance between the silicon clusters decreases below 3 nm. In addition, electric-field-induced quenching of the photoluminescence from silicon clusters and Er 3+ is observed. These results indicate that the EL excitation process of Er 3+ ions is governed by the direct impact excitation by hot electrons. An increase of the silicon nanocluster density causes direct tunneling of electrons between silicon clusters, thus reducing the population of energetic hot electrons for impact excitation of Er 3+ ions.