The overlap of the principal luminescence band of the erbium ion with the low-loss optical transmission window of silica optical fibres, along with the drive for integration of photonics and silicon technology, has generated intense interest in doping silicon with erbium to produce a silicon-based optical source Silicon is a poor photonic material due to its very short non-radiative lifetime and indirect band gap, but it has been hoped that the incorporation of optically active erbium ions into silicon will permit the development of silicon-based light sources that will interface with both CMOS technology and optical fibre communications Some years into this activity, there have now been a wide range of experimental studies of material growth techniques, optical, physical and electrical properties, along with a considerable body of theoretical work dealing with the site of the erbium ion in silicon, along with activation and deactivation processes This paper reviews the current state of what remains an active field, summarizing results from a range of studies conducted over the last few years, and points to further developments by considering the prospects for successful photonic integration of erbium and silicon

https://iopscience.iop.org/article/10.1088/0268-1242/20/12/R02/pdf

Erbium in silicon

An all-silicon in-plane micron-size electrically driven resonant cavity light emitting device (RCLED) based on slotted waveguide is proposed and modeled. The device consists of a microring resonator formed by Si/SiO2 slot-waveguide with a low-index electroluminescent material (erbium-doped SiO2) in the slot region. The geometry of the slot-waveguide permits the definition of a metal-oxide-semiconductor (MOS) configuration for the electrical excitation of the active material. Simulations predict a quality factor Q of 6,700 for a 20-μm-radius electrically driven microring RCLED capable to operate at a very low bias current of 0.75 nA. Lasing conditions are also discussed.

Electrically driven silicon resonant light emitting device based on slot-waveguide

It is demonstrated that the photoluminescence intensity of optically active erbium ions positioned in close proximity of anisotropic Ag nanoparticles is significantly enhanced if the nanoparticles support plasmon modes that are resonant with the erbium emission. In addition, the photoluminescence intensity enhancement is found to be polarized corresponding to polarization of these plasmon modes. Both observations demonstrate that the photoluminescence enhancement is due to coupling of the Er3+ I13∕24−I15∕24 transition dipoles with plasmon modes in the Ag nanoparticles. As this coupling mechanism is known to affect the emission rate, metal nanoparticles provide an opportunity to reduce the effect of temperature or concentration quench processes that are known to occur in a wide range of erbium-doped materials.

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Plasmon-enhanced erbium luminescence

Routes toward silicon-based lasers

Bright green electroluminescence with luminance up to 2800cd∕m2 is reported from indium-tin-oxide∕SiO2:Tb∕Si metal-oxide-semiconductor devices. The SiO2:Tb3+ gate oxide was prepared by thermal oxidation followed by Tb+ implantation. Electroluminescence and photoluminescence properties were studied with variations of the Tb3+ ion concentration and the annealing temperature. The optimized device shows a high external quantum efficiency of 16% and a luminous efficiency of 2.1lm∕W. The excitation processes of the strong green electroluminescence are attributed to the impact excitation of the Tb3+ luminescent centers by hot electrons and the subsequent crossrelaxation from D35 to D45 energy levels. Light-emitting devices with micrometer size fabricated by the standard metal-oxide-semiconductor technology are demonstrated.

/pdf/bright-green-electroluminescence-from-tb3-in-silicon-metal-2m2v1z3ttu.pdf

Bright green electroluminescence from Tb3+ in silicon metal-oxide-semiconductor devices

We report on the fabrication and performances of highly efficient Si-based light sources. The devices consist of MOS structures with erbium (Er) implanted in the thin gate oxide. They exhibit strong 1.54 μm electro-luminescence (EL) at 300 K with a 10% external quantum efficiency, comparable to that of standard light emitting diodes using III–V semiconductors. Emission at different wavelengths has been achieved incorporating different rare earths (terbium (Tb) and ytterbium (Yb)) in the gate dielectric. The external quantum efficiency depends on the rare-earth ions incorporated and ranges from 10% (for a Tb doped MOS) to 0.1% (for an Yb doped MOS). RE excitation is caused by hot electrons impact and oxide wearout limits the reliability of the devices. Much more stable light emitting MOS devices have been fabricated using Er-doped silicon rich oxide (SRO) films as gate dielectric. These devices show a high stability, with an external quantum efficiency reduced to 0.2%. In these devices, Er pumping occurs partially by hot electrons and partially by energy transfer from the Si nanostructures to the rare-earth ions, depending on Si excess in the film. Si/SiO 2 Fabry–Perot microcavities have been fabricated to enhance the external quantum emission along the cavity axis and the spectral purity of emission from the films that are used as active media to fabricate a Si-based resonant cavity light emitting diode (RCLED). These structures are fabricated by chemical vapour deposition on a silicon substrate. The microcavities are tuned at different wavelengths (nm): 540, 980 and 1540 (characteristic emission wavelengths, respectively, for Tb, Yb and Er). The reflectivity of the microcavities is about 97% and the quality factor ranges from 60 (for the cavity tuned at 980 nm) to 95 (for the cavities tuned at 540 and 1540 nm).

High efficiency light emitting devices in silicon

We report on the fabrication and performances of the most efficient Si-based light sources. The devices consist of MOS structures with erbium (Er) implanted in the thin gate oxide. The devices exhibit strong 1.54 μm electroluminescence at 300K with a 10% external quantum efficiency, comparable to that of standard light emitting diodes using III-V semiconductors. Emission at different wavelenghts has been achieved incorporating different rare earths (Ce, Tb, Yb, Pr) in the gate dielectric. The external quantum efficiency depends on the rare earth ions incorporated and ranges from 10% (for an Tb doped MOS) to 0.1% (for an Yb doped MOS). RE excitation is caused by hot electrons impact and oxide wearout limits the reliability of the devices. Much more stable light emitting MOS devices have been fabricated using Er-doped SRO (Silicon Rich Oxide) films as gate dielectric. These devices show a high stability, with an external quantum efficiency reduced to 0.2%. In these devices Er pumping occurs part by hot electrons and part by energy transfer from the Si nanostructures to the rare earth ions, depending by Si excess in the film. Si/SiO2 Fabry-Perot microcavities have been fabricated to enhance the external quantum emission along the cavity axis and the spectral purity of emission from the films that are used as active media to realize a Si based RCLED (resonant cavity light emitting diode). These structures are realized by chemical vapour deposition on a silicon substrate. The microcavities are tuned at different wavelengths: 540nm, 980nm and 1540nm (characteristic emission wavelengths respectively for Tb, Yb and Er). The reflectivity of the microcavities is of 97% and the quality factor ranges from 60 (for the cavity tuned at 980nm) to 95 (for the cavities tuned at 540nm and 1540nm).

High Efficiency Light Emission Devices in Silicon

A device for emitting optical radiation is integrated on a substrate of semiconductor material. The device includes an active layer having a main area for generating radiation, and first and second electro-conductive layers having an electric signal that generates an electric field to which an exciting current is associated. In the device, a dielectric region is formed between the first and second layers to space peripheral portions of the first and second layers so that the electric field in the main area is higher than the electric field between the peripheral portions, thereby facilitating generation of the exciting current in the main area. A method of manufacturing is also disclosed.

Optical radiation emitting device and method of manufacturing same

A galvanic optocoupler of the type monolithically integrated on a silicon substrate and having at least one luminous source and a photodetector interfaced by means of a galvanic insulation layer. The photodetector can be a phototransistor realized in the silicon substrate, and the galvanic insulation layer ( 40 ) is a passivation layer of this phototransistor. The luminous source, above the galvanic insulation layer includes an integrated LED having a first and second polysilicon layer with function of cathode and anode, respectively, these first and second layers enclosing at least one light emitter layer, in particular a silicon oxide layer enriched with silicon (SRO). An integration process of a galvanic optocoupler thus made, in particular in BCD3s technology is provided.

Galvanic optocoupler and method of making

We report on the fabrication and performances of highly efficient Si-based light sources. The devices consist of MOS structures with erbium (Er) implanted in the thin gate oxide. The devices exhibit strong 1540 nm electroluminescence at 300K with a 10% external quantum efficiency, comparable to that of standard light emitting diodes using III-V semiconductors. Emission at different wavelenghts has been achieved incorporating different rare earths (Ce, Tb, Yb, Pr) in the gate dielectric. RE excitation is caused by hot electrons impact and oxide wearout limits the reliability of the devices. Much more stable light emitting MOS devices have been fabricated using Er-doped SRO (Silicon Rich Oxide) films as gate dielectric. These devices show a high stability, with an external quantum efficiency reduced to 0.2%. In these devices different pumping mechanisms for the Er ions are simultaneously operating: Er can be excited by direct hot electron impact (like in stoichiometric oxide MOS) and by energy transfer from excited Si nanostructures, depending on the Si excess in the film. We propose a model to describe the electrical conduction mechanism in a Silicon Rich Oxide film. The electrical characteiristics can be fitted by a Schottky emission mechanism at low electrical fields and by a SCLC(Space Charge Limited Conduction) model for high elctrical fields. Data obtained from C-V measurements confirm the proposed model.

Mariantonietta Monaco

Papers

High efficiency light emitting devices in silicon

High Efficiency Light Emission Devices in Silicon

Optical radiation emitting device and method of manufacturing same

Galvanic optocoupler and method of making

Si-based rare-earth-doped light-emitting devices