Fabrication and Analysis of Epitaxially Grown Ge $_{1-x}$ Sn $_x$ Microdisk Resonator With 20-nm Free-Spectral Range
TL;DR: In this article, a whispering gallery mode (WGM) microdisk resonator based on Ge1-xSnx grown by molecular beam epitaxy (MBE) was fabricated and characterized.
Abstract: In this work, a whispering gallery mode (WGM) microdisk resonator based on Ge1-xSnx grown by molecular beam epitaxy (MBE) was fabricated and characterized. Various process conditions and different Sn contents (4% and 1%) were explored to confirm the feasibility of Ge1-xSnx for microcavity device operation. Optical modes with wavelengths in the infrared (IR) range beyond 1550 nm were successfully confined in the devices fabricated with different diameters, and free-spectral ranges (FSRs) near 20 nm were obtained.
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Dissertation•
01 Apr 2020
TL;DR: In this article, Galluccio et al. presented a GeSn semiconductor for micro-nanoelectronic applications for the purpose of micro-noelectric applications.
Abstract: Title GeSn semiconductor for micro-nanoelectronic applications Author(s) Galluccio, Emmanuele Publication date 2020-04 Original citation Galluccio, E. 2020. GeSn semiconductor for micro-nanoelectronic applications. PhD Thesis, University College Cork. Type of publication Doctoral thesis Rights © 2020, Emmanuele Galluccio. https://creativecommons.org/licenses/by-nc-nd/4.0/ Item downloaded from http://hdl.handle.net/10468/10549
10 citations
TL;DR: In this paper, a SiGeSn multi-quantum well-laser was modeled with k·p theory to adapt transport, optical gain and optical loss models to this material system (drift-diffusion, thermionic emission, gain calculations, free carrier absorption, and intervalence band absorption).
Abstract: We present comprehensive modeling of a SiGeSn multi-quantum well laser that has been previously experimentally shown to feature an order of magnitude reduction in the optical pump threshold compared to bulk lasers. We combine experimental material data obtained over the last few years with k·p theory to adapt transport, optical gain, and optical loss models to this material system (drift-diffusion, thermionic emission, gain calculations, free carrier absorption, and intervalence band absorption). Good consistency is obtained with experimental data, and the main mechanisms limiting the laser performance are discussed. In particular, modeling results indicate a low non-radiative lifetime, in the 100 ps range for the investigated material stack, and lower than expected Γ-L energy separation and/or carrier confinement to play a dominant role in the device properties. Moreover, they further indicate that this laser emits in transverse magnetic polarization at higher temperatures due to lower intervalence band absorption losses. To the best of our knowledge, this is the first comprehensive modeling of experimentally realized SiGeSn lasers, taking the wealth of experimental material data accumulated over the past years into account. The methods described in this paper pave the way to predictive modeling of new (Si)GeSn laser device concepts.
9 citations
TL;DR: In this article, a nanowire p-type metal-oxide-semiconductor field effect transistor (PMOSFET) coaxially having a Si core and a Ge peripheral channel is designed and characterized by device simulations.
Abstract: In this work, a nanowire p-type metal–oxide–semiconductor field-effect transistor (PMOSFET) coaxially having a Si core and a Ge peripheral channel is designed and characterized by device simulations. Owing to the high hole mobility of Ge, the device can be utilized for high-speed CMOS integrated circuits, with the effective confinement of mobile holes in Ge by the large valence band offset between Si and Ge. Source/drain doping concentrations and the ratio between the Si core and Ge channel thicknesses are determined. On the basis of the design results, the channel length is aggressively scaled down by evaluating the primary DC parameters in order to confirm device scalability and low-power applicability in sub-10-nm technology nodes.
8 citations
TL;DR: A vibration-displacement immunization model is proposed to measure the free spectral range of a resonant cavity by using a laser self-mixing velocimeter, which can effectively get rid of low measurement accuracy related to the self- Mixing vibration system due to the vibratory displacement.
Abstract: In this paper, a vibration-displacement immunization model is proposed to measure the free spectral range of a resonant cavity by using a laser self-mixing velocimeter. The validity of this method is demonstrated by the experimental results, which can effectively get rid of low measurement accuracy related to the self-mixing vibration system due to the vibratory displacement. According to the periodic waveform separation characteristic of the self-mixing velocity signal, the free spectral range of a multilongitudinal mode diode laser is calculated to be 88.24 GHz. Moreover, the influences of different target velocities and signal sampling frequencies on the free spectral range have been analyzed in detail from the theoretical analysis. In the case of high signal sampling rate and low velocity, from which the undistorted velocity signal waveform at the integral order external cavity mode keeps stable, it is possible to obtain relatively accurate measured results.
6 citations
TL;DR: In this article, a nano-structured silicon germanium (Si 1− x Ge x ) optical waveguide with different Ge fraction (x ) was evaluated by both optical simulations and theoretical calculations, which are mainly found in the enhanced optical confinement and better interfacing capability.
Abstract: Optical interconnect in integrated optoelectronic circuits is one of the promising next-generation technologies for replacing metalized interconnect. Efforts have been made to use silicon (Si)-compatible materials such as germanium (Ge) and Ge-buffered III–V compound semiconductors, along with Si, as optical sources for Si and group-IV integrated optoelectronic systems. This opens the possibility that higher fraction of Ge with its high refractive index ( n ) can be incorporated in Si waveguide for optical interconnect and the graftability between Si and group-IV or III–V materials would be improved in silicon photonics. In this work, advantageous features of nano-structured silicon germanium (Si 1− x Ge x ) optical waveguide with different Ge fraction ( x ) were evaluated by both optical simulations and theoretical calculations, which are mainly found in the enhanced optical confinement and better interfacing capability. Along with the SiGe waveguide, performance of Si 1− x Ge x microring resonator under material loss in the effect of extinction coefficient ( k ) has been investigated to suggest the necessity of optimizing the Ge content in Si 1− x Ge x passive devices. While carrying out the establish design criteria, n and k have been modelled in closed-form functions of Ge fraction at 1550 nm. Furthermore, by examining high-resolution transmission electron microscopy (HR-TEM) images, process compatibility of Ge with either group-IV alloys or III–V compound semiconductors is confirmed for the monolithically integrated photonic circuits.
4 citations
References
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TL;DR: A high-Q SPP whispering-gallery microcavity that is made by coating the surface of a high- Q silica microresonator with a thin layer of a noble metal is demonstrated and Q factors of 1,376 ± 65 can be achieved in the near infrared for surface-plasmonic whispering- gallery modes at room temperature.
Abstract: Surface plasmon polaritons (SPPs) are electron density waves excited at the interfaces between metals and dielectric materials (1). Owing to their highly localized electromagnetic fields, they may be used for the transport and manipulation of photons on subwavelength scales (2-9). In particular, plasmonic resonant cavities represent an application that could exploit this field compression to create ultrasmall-mode-volume devices. A key figure of merit in this regard is the ratio of cavity quality factor, Q (related to the dissipation rate of photons confined to the cavity), to cavity mode volume, V (refs 10, 11). However, plasmonic cavity Q factors have so far been limited to values less than 100 both for visible and near-infrared wavelengths (12-16). Significantly, such values are far below the theoretically achievable Q factors for plasmonic resonant structures. Here we demonstrate a high-Q SPP whispering-gallery microcavity that is made by coating the surface of a high-Q silica microresonator with a thin layer of a noble metal. Using this structure, Q factors of 1,376 ± 65 can be achieved in the near infrared for surface-plasmonic whispering-gallery modes at room temperature. This nearly ideal value, which is close to the theoretical metal-loss-limited Q factor, is attributed to the suppression and minimization of radiation and scattering losses that are made possible by the geometrical structure and the fabrication method. The SPP eigenmodes, as well as the dielectric eigenmodes, are confined within the whispering-gallery microcavity and accessed evanescently using a single strand of low-loss, tapered optical waveguide (17, 18). This coupling scheme provides a convenient way of selectively exciting and probing confined SPP eigenmodes. Up to 49.7 per cent of input power is coupled by phase-matching control between the microcavity SPP and the tapered fibre eigenmodes.
464 citations
TL;DR: This Carousel trap, caused by attractive optical gradient forces, interfacial interactions, and the circulating momentum flux, considerably enhances the rate of transport to the sensing region, thereby overcoming limitations posed by diffusion on such small area detectors.
Abstract: Individual nanoparticles in aqueous solution are observed to be attracted to and orbit within the evanescent sensing ring of a Whispering Gallery Mode micro-sensor with only microwatts of driving power. This Carousel trap, caused by attractive optical gradient forces, interfacial interactions, and the circulating momentum flux, considerably enhances the rate of transport to the sensing region, thereby overcoming limitations posed by diffusion on such small area detectors. Resonance frequency fluctuations, caused by the radial Brownian motion of the nanoparticle, reveal the radial trapping potential and the nanoparticle size. Since the attractive forces draw particles to the highest evanescent intensity at the surface, binding steps are found to be uniform.
250 citations
"Fabrication and Analysis of Epitaxi..." refers background in this paper
...…used for conventional dielectric resonators in advanced radio frequency (RF) circuits, optical communication systems, and biosensing devices because of their simple device structure, high quality factor, and the possibility of both transverse electric (TE) and transverse magnetic (TM) mode…...
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TL;DR: In this article, the Rayleigh-Ritz method and the finite element method nongenerating spurious solutions are employed for analysis of whispering gallery modes (WGMs) in cylindrical single-crystal anisotropic dielectric resonators.
Abstract: The Rayleigh-Ritz method and the finite element method nongenerating spurious solutions are employed for analysis of whispering gallery modes (WGMs) in cylindrical single-crystal anisotropic dielectric resonators. These methods allow accurate computation of the resonant frequencies, the Q-factors (depending on the dielectric and on the conductor losses), and the electromagnetic field distributions for all WGMs in the presence of additional elements like metal shields, MIC substrate, or supports. Different families of modes are studied both theoretically and experimentally. The mode coupling phenomenon is investigated. A WGM single-crystal quartz resonator is presented having an unloaded Q-factor greater than 30000 at about 100 GHz, including radiation and dielectric losses. >
88 citations
TL;DR: In this article, the optical energy gap of Ge1−xSnx alloys has been determined from transmittance measurements, using a fast-Fourier-transform infrared interferometer, showing that the change from indirect to direct band gap occurs at a lower critical Sn concentration than the value predicted from the virtual crystal approximation, tight binding, and pseudopotential models.
Abstract: The optical energy gap of Ge1−xSnx alloys has been determined from transmittance measurements, using a fast-Fourier-transform infrared interferometer. Our results show that the change from indirect to direct band gap occurs at a lower critical Sn concentration (xc) than the value predicted from the virtual crystal approximation, tight binding, and pseudopotential models. However, a close agreement between the experimental results and the predictions with deformation potential theory is observed. The concentration xc, which is theoretically expected to be 0.09, actually it is observed to lie between 0.10
80 citations
"Fabrication and Analysis of Epitaxi..." refers background in this paper
...To ease integration with silicon electronics, group IV species and their alloys are attracting great attention as good candidates for the active material [5]....
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TL;DR: In this paper, the authors investigated the behaviors of the carrier mobility and concentration of the undoped Ge1-xSnx layers epitaxially grown on silicon-on-insulator (SOI) substrates.
Abstract: We have investigated the behaviors of the carrier mobility and concentration of the undoped Ge1-xSnx layers epitaxially grown on silicon-on-insulator (SOI) substrates. Hall measurement revealed the conduction of holes excited from acceptor levels related to vacancy defects whose concentration was as high as 1018 cm-3 in Ge1-xSnx layers. The temperature dependences of the carrier mobility and concentration in the valence band was estimated by reducing the parallel conduction component in the impurity band. The incorporation of Sn at a content lower than 4.0% hardly degraded the hole mobility of heteroepitaxial Ge1-xSnx layers. In contrast, the mobility of the Ge1-xSnx layers was improved by reducing the carrier concentration of the Ge1-xSnx layers by Sn incorporation compared with that of the Ge layer formed under the same growth and annealing conditions. This result suggests that the incorporation of Sn into Ge leads to reducing the hole concentration of the electrically active vacancy defects due to the formation of Sn-vacancy pairs.
79 citations