Er-doped Silicon-rich Silicon Oxide Research Articles

Silicon-rich oxynitride hosts for 1.5μm Er3+ emission fabricated by reactive and standard RF magnetron sputtering

Abstract This study compares the erbium emission from different Si-rich silicon oxynitrides matrices fabricated by magnetron sputtering. The Er-doped layers were grown by two different sputtering configurations: (i) standard co-sputtering of three confocal targets (Er 2 O 3 , Si 3 N 4 and SiO 2 ) under Ar plasma, and (ii) reactive co-sputtering under Ar + N 2 plasma of either three (Er 2 O 3 , pure Si and SiO 2 ) or two targets (Er 2 O 3 and pure Si). The last reactive configuration was found to offer the best Er 3+ PL intensity at 1.5 μm. This highest PL intensity was found comparable to the corresponding emission from Er-doped silicon-rich silicon oxide.

1.54 μ m emission mechanism in Er-doped silicon-rich silicon oxides

Silicon-rich silicon oxide (SRSO) and Er-doped SRSO (SRSO:Er) thin films were formed by pulsed laser deposition, and characterized by photoluminescence (PL), x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD), and UV-visible transmission in order to clarify the 1.54 μm emission mechanism in the SRSO:Er films. The oxygen content of the films was varied by the adjustment of oxygen partial pressure. The behavior of the 1.54 μm PL with oxygen partial pressure combined with XPS and XRD data show that the 1.54 μm emission intensity is related to the amount of SiOx phase. This conclusion is well supported by the measurements of UV-visible transmission. In many previous papers, the 1.54 μm emission is associated with Si nanocrystals, but in our study the correlation between 1.54 μm emission intensity and the amount of SiOx phase is much clearer.

Submicrosecond fluorescence dynamics in erbium-doped silicon-rich silicon oxide multilayers

The energy transfer process between amorphous silicon nanoparticles and erbium ions in Er-doped silicon-rich silicon oxide is investigated by fluorescence dynamics measurements. A fast decay is observed in the wavelength range of the radiative relaxation of erbium excited ions at 1.53 μm. Alternatively to a previous interpretation, we assign this fast decay to emission of deep traps induced by Si-based sensitizers of Er3+ ions, which emit in the visible and the infrared region.

The evolution of the fraction of Er ions sensitized by Si nanostructures in silicon-rich siliconoxide thin films

Photoluminescence (PL) and time-resolved PL experiments as a function of the elaborationprocess are performed on Er-doped silicon-rich silicon oxide (SRO:Er) thin films grown underNH3 atmosphere. These PLmeasurements of the Er3+ emission at 1.54 µm under non-resonant pumping with the Er f–f transitions are obtained for differentEr3+ concentrations, ranging from 0.05 to 1.4 at.%, and various post-growth annealingtemperatures of the layers. High resolution transmission electron microscopy(HRTEM) and energy-filtered TEM (EFTEM) analysis show a high density of Sinanostructures composed of amorphous and crystalline nanoclusters varying from2.7 × 1018 to1018 cm−3 as a function of the post-growth annealing temperature. Measurements of PL lifetime and effectiveEr excitation cross section for all the samples under non-resonant optical excitation with theEr3+ atomic energy levels show that the number ofEr3+ ions sensitized by the silicon-rich matrix decreases as the annealing temperature is increased from500 to1050 °C. The origin of this effect is attributed to the reduction of the density of sensitizers for Erions in the SRO matrix when the annealing temperature increases. Finally, extendedx-ray absorption fine-structure spectroscopy (EXAFS) shows a strong correlationbetween the number of emitters and the mean local order around the erbium ions.

Structural and optical characteristics of Er-doped SRSO layers deposited by the confocal sputtering technique

Er-doped silicon-rich silicon oxide layers have been grown at 600 °C by magnetron co-sputtering of three confocal cathodes (Si, SiO 2 and Er 2O 3) in pure argon plasma. The structural and optical properties of the layers were examined in the function of deposition and annealing conditions. It was shown that the increase of the RF power density applied on the Si cathode from 0.74 to 2.07 W cm −2, while maintaining constant RF power on the two other cathodes, allows a fine engineering of the Si excess from 5 to 15 at%. The Er content was evaluated to 1×10 21 at cm −3. A high Er 3+ emission was observed under non-resonant (476 nm) excitation from as-deposited layers, which was significantly improved after annealing at 600 °C. The Er PL was found to be much more intense than the best samples reported so far, which was annealed at 900 °C and contains, however, lower Er content (5.4×10 20 at cm −3) and Si excess (7 at% of Si). The Er emission lifetime was found to be about 6 ms for low Si excess (5 at%) and 1–2 ms for high Si excess. Upon reducing the Er content by a factor of three, the Er 3+ PL intensity was further increased and the lifetime reached 5.5 ms, suggesting a notable increase of the fraction of coupled Er ions.

Effect of ion-irradiation induced defects on the nanocluster Si∕Er3+ coupling in Er-doped silicon-rich silicon oxide

The effect of ion-irradiation induced defects on the nanocluster Si∕Er3+ coupling in Er-doped silicon-rich silicon oxide (SRSO) thin film is investigated. Er-doped SRSO, which consists of silicon nanoclusters (nc-Si) in a SiO2 matrix, was fabricated using electron-cyclotron resonance plasma enhanced chemical vapor deposition using SiH4 and O2 with concurrent sputtering of Er followed by a high temperature annealing. Defects were introduced into the film via irradiation with 3MeV Si ions and subsequently removed by high temperature annealings. The authors find that ion irradiation reduces Er3+ luminescence from SRSO films, even when the excitation cross section and luminescence efficiency of Er3+ ions are completely restored. On the other hand, ion irradiation increases the intrinsic nc-Si luminescence and has little effect on the Er3+ luminescence from a similarly prepared, Er-doped SiO2 film, indicating that the presence of irradiation induced defects in the initial amorphous film can reduce the number of Er3+ ions available for nc-Si mediated luminescence by as much as a factor of 3.

Fabrication and Optical Properties of Erbium-Doped Silicon-Rich Silicon Oxide Nanofibers

Synthesis of Er-doped silicon-rich silicon oxide (SRSO) nanofibers bundled into yarns was successfully achieved. Photoluminescence (PL) studies of the yarns detected a strong and sharp band at 1.530 μm at room temperature, which is attributed to Er ions excited by energy transfer from photogenerated carriers in Si nanoclusters (nc-Si). The effective absorption cross-section of the first excited state of the Er ions is estimated to be 1.86 x 10 -16 cm -2 , higher by several orders of magnitude than that in an Er-doped SiO 2 host, due to the presence of nc-Si that serves as a sensitizer in the SRSO nanofibers. In order to investigate the luminescence mechanism of the Er ions, PL spectra excited by incident light of different wavelengths were measured. We found that both the peak position and line shape of the Er ion emissions are unaffected by the incident wavelength. The results indicate that the Er ion luminescence in the SRSO nanofibers is completely dominated by ions located at sites that are strongly coupled to the carriers in the nc-Si. We also found that the intensity of luminescence decreases by less than 30% as the temperature is raised from 10 K to room temperature, indicating that thermal quenching is significantly reduced.

Er-doped Silicon-rich Silicon Oxide (SRSO) Thin FilmsDeposited by ECR-PECVD at High Temperatures

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Influence of Er concentration on the emission properties of Er-doped Si-rich silica films obtained by reactive magnetron co-sputtering

Er-doped silicon-rich silicon oxide (SRSO) thin films have been fabricated by reactive magnetron sputtering of a pure silica target topped by chips of Er2O3. The incorporation of silicon excess in the films is due to the introduction of hydrogen in the plasma which reduces accordingly the oxygen released by the silica target. The incorporated Er content [Er] in the films was controlled by the sputtered surface ratio of Er2O3 chips with respect to that of silica target. The photoluminescence (PL) intensity at 1.54 μm from samples obtained with different [Er] values and annealing temperature were compared for the same amount of Si excess and interpreted in terms of sensitizing action of Si nanoclusters (Si–NCs) towards the neighboring Er ions. Some onset of concentration-related effects (up conversion, quenching) was suspected for [Er] ∼3 × 1020 cm−3 through the decrease of the lifetime emission from ∼6 ms for [Er] = 5 × 1019 cm−3 to about 3.5 ms. These effects were compensated by a better coupling rate between the Si–NCs and the neighbouring Er ions. This was achieved through some adjustments of the processing parameters: the decrease of the plasma pressure that led to the improvement of the PL by a factor of 3, and the decrease of the annealing temperature from 1100 °C to 900 °C that induced a 2.5 times increase of the 1.54 μm emission.

The effects of ambient oxygen pressure on the 1.54 μm photoluminescence of Er-doped silicon-rich silicon oxide films grown by laser ablation of a Si+Er target

We fabricated Er-doped silicon-rich silicon oxide (SRSO:Er) films by pulsed laser deposition. A Si+Er target consisting of an Er metallic strip and a silicon disk was adopted with a goal to achieve a convenient control of the Er and oxygen density in the film. We found that the photoluminescence (PL) at 1.54 μm is highly dependent on the ambient oxygen pressure, which determines the relative ratio of Si-Si, SiOx, and SiO2 phase in the film. The PL intensity increased drastically with increase in the annealing temperature and reached the maximum intensity at 500 °C.

Er3+ Photoluminescence from Er-doped Silicon-Rich Silicon Oxide Films Deposited by Laser Ablation of a Si:Er Target in an Oxygen Atmosphere

We have developed a new pulsed laser deposition method for fabricating Er-doped silicon-rich silicon oxide (SRSO:Er) films. A target composed of a pure Si disk and an Er metal strip was ablated by a line-focused laser beam in oxygen atmosphere. The oxygen concentration that determines the relative concentrations of the three phases (Si–Si, SiOx, and SiO2) in the film was easily controlled by varying the ambient oxygen pressure. The photoluminescence intensity at 1.54 µm from Er3+ ions was strongly dependent on the amount of the Si–Si phase in the SRSO:Er films.

Optical gain at 1.54 μm in erbium-doped silicon nanocluster sensitized waveguide

Optical gain at 1.54 μm in erbium-doped silicon-rich silicon oxide (SRSO) is demonstrated. Er-doped SRSO thin film was fabricated by electron-cyclotron resonance enhanced chemical vapor deposition of silicon suboxide with concurrent sputtering of erbium followed by a 5 min anneal at 1000 °C. Ridge-type single mode waveguides were fabricated by wet chemical etching. Optical gain of 4 dB/cm of an externally coupled signal at 1.54 μm is observed when the Er is excited via carriers generated in the Si nanoclusters by the 477 nm line of an Ar laser incident on the top of the waveguide at a pump power of 1.5 W cm−2.

Room-temperature 1.54 μm electroluminescence from Er-doped silicon-rich silicon oxide films deposited on n+-Si substrates by magnetron sputtering

Room-temperature 1.54 μm electroluminescence (EL) was compared for Au/SiO2:Er/n+-Si and Au/SiOx:Si:Er/n+-Si diodes under reverse bias. The 18 nm thick SiO2:Er and SiOx:Si:Er films were deposited by the magnetron sputtering technique. The maximum of the EL intensity was reached after annealing at 900 °C (SiO2:Er) and 800 °C (SiOx:Si:Er). The threshold potential of the EL was about 4 and 6 V for the Au/SiOx:Si:Er/n+-Si and Au/SiO2:Er/n+-Si diodes, respectively. The power efficiency was larger for the Au/SiOx:Si:Er/n+-Si diode than that for the Au/SiO2:Er/n+-Si diode by six times. Our experimental results demonstrate that the existence of Si nanoclusters reduces the threshold potentials of the EL and strongly enhances the power efficiency for Er3+ EL.

Exciton-mediated excitation of Er3+ in Erbium-doped silicon rich silicon oxide

AbstractExciton-mediated excitation of Er3+ in erbium doped silicon rich silicon oxide (SRSO) is investigated. Er-doped SRSO films were fabricated by electron cyclotron-resonance plasmaenhanced chemical vapor deposition of Er-doped SiOx (x < 2) using SiH4 and O2 as source gases and co-sputtering of Er, followed by an anneal at 950 °C. Very weak visible luminescence from Si nanocluster relative to Er3+ luminescence were observed, indicating a very efficient excitation of Er3+ ions by Si nanoclusters. From detailed modeling and analysis of time-resolved Er3+ luminescence as the excitation duration and excitation power, we conclude that exciton-erbium coupling is dominant over exciton-nanocluster. The results are consistent with the proposal that the luminescent Er3+ ions are located predominantly in the SiO2 layer.

Carrier-induced Er3+ luminescence quenching of erbium-doped silicon-rich silicon oxide

The quenching of Er3+ luminescence induced by carriers in silicon nanoclusters of Er-doped silicon-rich silicon oxide (SRSO) is investigated. The dependence of Er3+ photoluminescence intensities and lifetimes upon the temperature, pump power, and the background illumination intensity shows that in SRSO, Auger-type interactions with carriers in the host matrix that can severely limit the Er3+ luminescence efficiency are greatly suppressed. The results also show that efficient optoelectronic devices using Er-doped SRSO may be feasible.

Room-temperature photoluminescence and electroluminescence from Er-doped silicon-rich silicon oxide

Porous silicon was doped by Er ions using electroplating and was converted to silicon-rich silicon oxide (SRSO) by partial thermal oxidation at 900 °C. The room-temperature photoluminescence (PL) at ∼1.5 μm is intense and narrow (⩽15 meV) and decreases by less than 50% from 12 to 300 K. The PL spectrum reveals no luminescence bands related to Si-bandedge recombination, point defects, or dislocations and shows that the Er3+ centers are the most efficient radiative recombination centers. A light-emitting diode (LED) with an active layer made of Er-doped SRSO (SRSO:Er) was manufactured and room temperature electroluminescence at ∼1.5 μm was demonstrated.

Er-Doped Porous Silicon Led For Integrated Optoelectronics

AbstractPorous silicon (PSi) was doped by Er using electromigration from a solution and converted to Er-doped silicon-rich silicon oxide (SRSO:Er) by partial thermal oxidation at 600–950°C following densification at 1100°C in an inert atmosphere. Room-temperature photoluminescence (PL) at ∼1.5 μm is intense and decreases by less than 20% from 12 K to 300 K. The PL spectrum of SRSO:Er reveals no luminescence bands related to Si-bandedgerecombination, point defects or dislocations, and shows that the Er3+ centers are the most efficient radiative recombination centers. A light-emitting diode (LED) with an active layer made of SRSO:Er was manufactured using a pre-oxidation cleaning step to increase the quality of the interface between SRSO:Er and the top electrode. Room temperature electroluminescence at ∼1.5 μm was demonstrated.