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

Light emission from Si quantum dots

Orange and yellow-colored light emission has been achieved at room temperature in the same elecroluminescent device (ELD) made on GaN thin films codoped with Er and Eu. The GaN film was grown by molecular-beam epitaxy on Si (111) substrates using solid sources for Ga, Er and Eu and a plasma source for N2. Simple Schottky devices were fabricated on the GaN films using indium–tin oxide (ITO) transparent electrodes. ELD spectra show that the yellow and orange colors result from the combination of green emission from Er (537, 558 nm) and red emission from Eu (621 nm). A color change was observed with applied bias, producing yellow at higher bias (−100 V) and orange at lower bias (−70 V). We have fabricated both relatively small (∼250 μm) and large (1.45 mm) ELDs. Parameters for the chromaticity diagram were calculated to be x=0.382, y=0.605 for the yellow emission and x=0.467, y=0.523 for the orange emission. This work shows the possibility of achieving any intermediate color in the spectrum from green to red...

/pdf/voltage-controlled-yellow-or-orange-emission-from-gan-eg34fs7w75.pdf

Voltage-controlled yellow or orange emission from GaN codoped with Er and Eu

The Ln-AV-20 structure is able to incorporate several different Ln3+ ions, which emit in different spectral regions, enabling the possibility of multi-colour capability. Using a study of the energy transfer dynamics in Gd1−(a+b)TbaEub-AV-20 materials, we show that the emission chromaticity of these systems may be fine-tuned in the red–green spectral region simply by changing the excitation wavelength and/or the sample composition. We show that a study of the energy transfer kinetics, in these and in related materials, can provide useful insight when the design of a material with a specific emission profile is required. By replacing Gd3+ with Ce3+, a system with full-colour capability, Ce0.53Tb0.35Eu0.12-AV-20, has been prepared. The emission colour coordinates for this material at room-temperature are x,y = 0.34, 0.33, which is in good agreement with the values given by the CIE for a white standard.

Tuning the emission colour in mixed lanthanide microporous silicates: energy transfer, composition and chromaticity

During the last four decades, a remarkable research effort has been made to understand the physical properties of Si:Er material, as it is considered to be a promising approach towards improving the optical properties of crystalline Si. In this paper, we present a summary of the most important results of that research. In the second part, we give a more detailed description of the properties of Si/Si:Er multinanolayer structures, which in many aspects represent the most advanced form of Er-doped crystalline Si with prospects for applications in Si photonics.

/pdf/photonic-properties-of-er-doped-crystalline-silicon-4w4kpr99ws.pdf

Photonic Properties of Er-Doped Crystalline Silicon

Different Er centres in Si and their use for electroluminescent devices

/pdf/optically-active-si-er-layers-grown-by-the-sublimation-mbe-4ya5gx9su2.pdf

Optically active Si:Er layers grown by the sublimation MBE method

Depending on the doping and annealing conditions, as well as the oxygen content, erbium produces a big variety of different centres in silicon. These centres can be distinguished by their fine structure patterns seen both in luminescence and in excitation spectroscopy. Centres with a well-defined geometry of their constituents exhibit very sharp line spectra. Such centres can be excited via recombination of electron-hole pairs, produced in a forward biased diode, with surprisingly high quantum efficiency below 100 K — but they are strongly quenched at higher temperatures. Another type of spectrum — with a much higher line width (∼20 nm) and weak thermal quenching up to 370 K is obtained after annealing at temperatures above 950°C. This type of spectrum is identified as being due to Er in SiO 2− δ precipitates. Such centres have much smaller quantum efficiencies for forward bias excitation than for reverse bias. We discuss properties that are important for the realisation of LED structures based on this type of centres for room temperature (RT) operation.

Optimisation of Er centers in Si for reverse biased light emitting diodes

Status, Hopes and Limitations for the Si: Er-based 1.54 μm Emitter

Room-temperature electroluminescence is obtained from erbium-doped Si diodes for heavily Er- and oxygen-doped material. Such diodes exhibit under reverse bias excitation a characteristic, about 10–20 nm wide emission spectrum which has a striking similarity to erbium-implanted silica (SiO 2  : Er) in contrast to the sharp line spectra of isolated Er centers seen at lower temperatures. The wide spectrum is thus attributed to the inhomogeneously broadened emission from Er in amorphous SiO 2- δ precipitates. We show that the isolated centers can be transformed into Er-containing precipitates for sufficient Er- and O-doses by proper choice of the annealing temperature after implantation.

H. Preier

Papers

Different Er centres in Si and their use for electroluminescent devices

Optically active Si:Er layers grown by the sublimation MBE method

Optimisation of Er centers in Si for reverse biased light emitting diodes

Status, Hopes and Limitations for the Si: Er-based 1.54 μm Emitter

On the generation of optically active Er centers in Si light emitting diodes