Light-Emitting Diodes. (Monographs in Electrical and Electronic Engineering.) By A. A. Bergh and P. J. Dean. Pp. viii+591. (Clarendon: Oxford; Oxford University: London, 1976.) £22.

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Light-emitting diodes

Lasing is experimentally demonstrated in a direct bandgap GeSn alloy, grown directly onto Si(001). The authors observe a clear lasing threshold as well as linewidth narrowing at low temperatures.

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Lasing in direct-bandgap GeSn alloy grown on Si

Silicon photonics research can be dated back to the 1980s. However, the previous decade has witnessed an explosive growth in the field. Silicon photonics is a disruptive technology that is poised to revolutionize a number of application areas, for example, data centers, high-performance computing and sensing. The key driving force behind silicon photonics is the ability to use CMOS-like fabrication resulting in high-volume production at low cost. This is a key enabling factor for bringing photonics to a range of technology areas where the costs of implementation using traditional photonic elements such as those used for the telecommunications industry would be prohibitive. Silicon does however have a number of shortcomings as a photonic material. In its basic form it is not an ideal material in which to produce light sources, optical modulators or photodetectors for example. A wealth of research effort from both academia and industry in recent years has fueled the demonstration of multiple solutions to these and other problems, and as time progresses new approaches are increasingly being conceived. It is clear that silicon photonics has a bright future. However, with a growing number of approaches available, what will the silicon photonic integrated circuit of the future look like? This roadmap on silicon photonics delves into the different technology and application areas of the field giving an insight into the state-of-the-art as well as current and future challenges faced by researchers worldwide. Contributions authored by experts from both industry and academia provide an overview and outlook for the silicon waveguide platform, optical sources, optical modulators, photodetectors, integration approaches, packaging, applications of silicon photonics and approaches required to satisfy applications at mid-infrared wavelengths. Advances in science and technology required to meet challenges faced by the field in each of these areas are also addressed together with predictions of where the field is destined to reach.

https://iopscience.iop.org/article/10.1088/2040-8978/18/7/073003/pdf

Roadmap on silicon photonics

Hybrid silicon lasers based on bonded III–V layers on silicon are currently the best contenders for on-chip lasers for silicon photonics. On-chip silicon light sources are highly desired for use as electrical-to-optical converters in silicon-based photonics. Zhiping Zhou and Bing Yin of Peking University in China and Jurgen Michel of Massachusetts Institute of Technology assess the three main contenders for such light sources: erbium-based light sources, germanium-on-silicon lasers and III-V-based silicon lasers. They consider operating wavelength, pumping conditions, power consumption, thermal stability and fabrication process. The scientists regard the power efficiencies of electrically pumped erbium-based lasers as being too low and the threshold currents of germanium lasers as being too high. They conclude that III–V quantum dot lasers monolithically grown on silicon show the most promise for realizing on-chip lasers.

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On-chip light sources for silicon photonics

Abstract The emergence of silicon photonics over the past two decades has established silicon as a preferred substrate platform for photonic integration. While most silicon-based photonic components have so far been realized in the near-infrared (near-IR) telecommunication bands, the mid-infrared (mid-IR, 2–20-μm wavelength) band presents a significant growth opportunity for integrated photonics. In this review, we offer our perspective on the burgeoning field of mid-IR integrated photonics on silicon. A comprehensive survey on the state-of-the-art of key photonic devices such as waveguides, light sources, modulators, and detectors is presented. Furthermore, on-chip spectroscopic chemical sensing is quantitatively analyzed as an example of mid-IR photonic system integration based on these basic building blocks, and the constituent component choices are discussed and contrasted in the context of system performance and integration technologies.

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Mid-infrared integrated photonics on silicon: a perspective

We will present our recent work on III-V micro-cavity lasers monolithically grown on silicon substrates. The III-V material is directly grown using Template-Assisted-Selective-Epitaxy (TASE) within oxide cavities patterned using conventional lithographic techniques on top of the silicon substrate. This allows for the local integration of single-crystal III-V active gain material. Two variations of this technique will be discussed; the direct growth of disc lasers and the two-step approach via a virtual substrate. Room temperature single-mode optically pumped lasing is achieved in GaAs micro-cavity lasers, and devices show a remarkably low shift of the lasing threshold (T0=170K) with temperature. Dependence on cavity geometry and pump power will be discussed.

Microcavity III-V lasers monolithically grown on silicon

GeSn and SiGeSn alloys have been grown by reactive gas source deposition using a commercial 8″ LPCVD tool. Both alloys exhibit a direct bandgap. Optically pumped GeSn Fabry-Perot and microdisc laser were fabricated etching strong undercuts to efficiently relax the strain. Lasing operation is demonstrated up to 135K and 140K, respectively. The wavelength is adjusted between 2.0 and 2.6 µm at 20K in dependence on the Sn concentration. Electroluminescence has been observed up to 300K in p-i-n GeSn homojunctions. Moreover first p-i-n SiGeSn/GeSn double heterostructures have been successfully deposited.

On the track towards an electrically pumped group IV laser

Oxidation-induced electron barrier enhancement at interfaces of Ge-based semiconductors (Ge, Ge1xSnx, SiyGe1xySnx) with Al2O3

The present chip technology is based on silicon with increasing number of other materials integrated into electrical circuits. This chapter presents a systematic photoluminescence (PL) study of compressively strained, direct-bandgap GeSn alloys, followed by the analysis of two different optical source designs. First, a direct bandgap GeSn light emitting diode (LED) will be characterized via power-and temperature-dependent electroluminescence (EL) measurements. Then, lasing will be demonstrated in a microdisk (MD) resonator under optical pumping. The integration of direct-bandgap GeSn-based devices as a light source for on-chip communications offers the possibility to monolithically integrate the complete photonic circuit within mainstream silicon technology. The chapter describes material properties using Ge0.875Sn0.125 epilayers of various thicknesses. Temperature-dependent integrated PL intensity is a suitable method to determine whether a semiconductor has a direct or indirect fundamental bandgap. In conclusion, the chapter presents growth and optical characterization of high-quality GeSn alloys with very high Sn content.

Stephan Wirths

Papers

Microcavity III-V lasers monolithically grown on silicon

On the track towards an electrically pumped group IV laser

Oxidation-induced electron barrier enhancement at interfaces of Ge-based semiconductors (Ge, Ge1xSnx, SiyGe1xySnx) with Al2O3

High Sn‐Content GeSn Light Emitters for Silicon Photonics

(Keynote) Epitaxy-Based Strain-Engineering Methods for Advanced Devices