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10 pages, 2353 KiB

Open AccessArticle

Reliability of Commercial UVC LEDs: 2022 State-of-the-Art

by Nicola Trivellin, Davide Fiorimonte, Francesco Piva, Matteo Buffolo, Carlo De Santi, Gaudenzio Meneghesso, Enrico Zanoni and Matteo Meneghini

Electronics 2022, 11(5), 728; https://doi.org/10.3390/electronics11050728 - 26 Feb 2022

Cited by 24 | Viewed by 3956

Abstract

With this study, we report on the reliability of the most recent commercial UVC LED devices. The current COVID-19 pandemic urged the development of antiviral technologies, and one of the most effective is based on UVC irradiation, which can be effectively achieved by [...] Read more.

With this study, we report on the reliability of the most recent commercial UVC LED devices. The current COVID-19 pandemic urged the development of antiviral technologies, and one of the most effective is based on UVC irradiation, which can be effectively achieved by means of Deep UV LEDs. The development of antiviral systems based on UVC LEDs strongly depends on their efficacy and reliability. We propose an in-depth analysis of four different state-of-the-art commercial LEDs suitable for disinfection applications. LEDs have been subjected to a controlled stress test near their application limits, and their reliability and characteristics have been analyzed and studied. Results indicate a still limited reliability, with a degradation possibly related to an increase in Shockley–Read–Hall (SRH) recombination. Finally, some relevant product design suggestions will be proposed based on the results of this work. Full article

(This article belongs to the Special Issue 10th Anniversary of Electronics: Recent Advances in Microelectronics and Optoelectronics)

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9 pages, 1728 KiB

Open AccessArticle

Simulated Hough Transform Model Optimized for Straight-Line Recognition Using Frontier FPGA Devices

by Alessandro Gabrielli, Fabrizio Alfonsi and Francesca Del Corso

Electronics 2022, 11(4), 517; https://doi.org/10.3390/electronics11040517 - 9 Feb 2022

Cited by 8 | Viewed by 2291

Abstract

The use of the Hough transforms to identify shapes or images has been extensively studied in the past using software for artificial intelligence applications. In this article, we present a generalization of the goal of shape recognition using the Hough transform, applied to [...] Read more.

The use of the Hough transforms to identify shapes or images has been extensively studied in the past using software for artificial intelligence applications. In this article, we present a generalization of the goal of shape recognition using the Hough transform, applied to a broader range of real problems. A software simulator was developed to generate input patterns (straight-lines) and test the ability of a generic low-latency system to identify these lines: first in a clean environment with no other inputs and then looking for the same lines as ambient background noise increases. In particular, the paper presents a study to optimize the implementation of the Hough transform algorithm in programmable digital devices, such as FPGAs. We investigated the ability of the Hough transform to discriminate straight-lines within a vast bundle of random lines, emulating a noisy environment. In more detail, the study follows an extensive investigation we recently conducted to recognize tracks of ionizing particles in high-energy physics. In this field, the lines can represent the trajectories of particles that must be immediately recognized as they are created in a particle detector. The main advantage of using FPGAs over any other component is their speed and low latency to investigate pattern recognition problems in a noisy environment. In fact, FPGAs guarantee a latency that increases linearly with the incoming data, while other solutions increase latency times more quickly. Furthermore, HT inherently adapts to incomplete input data sets, especially if resolutions are limited. Hence, an FPGA system that implements HT is inefficient for small sets of input data but becomes more cost-effective as the size of the input data increases. The document first presents an example that uses a large Accumulator consisting of 1100 × 600 Bins and several sets of input data to validate the Hough transform algorithm as random noise increases to 80% of input data. Then, a more specifically dedicated input set was chosen to emulate a real situation where a Xilinx UltraScale+ was to be used as the final target device. Thus, we have reduced the Accumulator to 280 × 280 Bins using a clock signal at 250 MHz and a few tens input points. Under these conditions, the behavior of the firmware matched the software simulations, confirming the feasibility of the HT implementation on FPGA. Full article

(This article belongs to the Special Issue 10th Anniversary of Electronics: Recent Advances in Microelectronics and Optoelectronics)

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11 pages, 2995 KiB

Open AccessArticle

Processing–Structure–Performance Relationship in Organic Transistors: Experiments and Model

by Rosalba Liguori, Antonio Facchetti, Gian Domenico Licciardo and Luigi Di Benedetto

Electronics 2022, 11(2), 197; https://doi.org/10.3390/electronics11020197 - 10 Jan 2022

Cited by 2 | Viewed by 2304

Abstract

In this paper, organic thin film transistors with different configurations are fabricated, and the effect on their performance when tailoring the semiconductor/insulator and semiconductor/contact interfaces through suitable treatments is analyzed. It is shown that the admittance spectroscopy used together with a properly developed [...] Read more.

In this paper, organic thin film transistors with different configurations are fabricated, and the effect on their performance when tailoring the semiconductor/insulator and semiconductor/contact interfaces through suitable treatments is analyzed. It is shown that the admittance spectroscopy used together with a properly developed electrical model turns out to be a particularly appropriate technique for correlating the performance of devices based on new materials in the manufacturing methods. The model proposed here to describe the equivalent metal–insulator–semiconductor (MIS) capacitor enables the extraction of a wide range of parameters and the study of the physical phenomena occurring in the transistors: diffusion of mobile ions through the insulator, charge trapping at the interfaces, dispersive transport in the semiconductor, and charge injection at the metal contacts. This is necessary to improve performance and stability in the case, like this one, of a novel organic semiconductor being employed. Atomic force microscopy images are also exploited to support the relationship between the semiconductor morphology and the electrical parameters. Full article

(This article belongs to the Special Issue 10th Anniversary of Electronics: Recent Advances in Microelectronics and Optoelectronics)

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12 pages, 4105 KiB

Open AccessArticle

Small-Signal Analysis of All-Si Microring Resonator Photodiode

by Yiwei Peng, Wayne V. Sorin, Stanley Cheung, Yuan Yuan, Zhihong Huang, Marco Fiorentino and Raymond G. Beausoleil

Electronics 2022, 11(2), 183; https://doi.org/10.3390/electronics11020183 - 7 Jan 2022

Cited by 9 | Viewed by 2386

Abstract

All-silicon microring resonator photodiodes are attractive for silicon photonics integrated circuits due to their compactness, wavelength division multiplexing ability, and the absence of germanium growth. To analyze and evaluate the performance of the microring photodiode, we derived closed-form expression of the response transfer [...] Read more.

All-silicon microring resonator photodiodes are attractive for silicon photonics integrated circuits due to their compactness, wavelength division multiplexing ability, and the absence of germanium growth. To analyze and evaluate the performance of the microring photodiode, we derived closed-form expression of the response transfer function with both electrical and optical behavior included, using a small-signal analysis. The thermo-optic nonlinearity resulting from optical loss and ohmic heating was simulated and considered in the model. The predicted response achieved close agreement with the experiment results, which provides an intuitive understanding of device performance. We analytically investigated the responsivity–bandwidth product and demonstrated that the performance is superior when the detuning frequency is zero. Full article

(This article belongs to the Special Issue 10th Anniversary of Electronics: Recent Advances in Microelectronics and Optoelectronics)

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11 pages, 2232 KiB

Open AccessArticle

Peculiarities of the Acoustic Wave Propagation in Diamond-Based Multilayer Piezoelectric Structures as “Me1/(Al,Sc)N/Me2/(100) Diamond/Me3” and “Me1/AlN/Me2/(100) Diamond/Me3” under Metal Thin-Film Deposition

by Gennady Kvashnin, Boris Sorokin, Nikita Asafiev, Viacheslav Prokhorov and Andrei Sotnikov

Electronics 2022, 11(2), 176; https://doi.org/10.3390/electronics11020176 - 7 Jan 2022

Cited by 5 | Viewed by 1926

Abstract

New theoretical and experimental results of microwave acoustic wave propagation in diamond-based multilayer piezoelectric structures (MPS) as “Me1/(Al,Sc)N/Me2/(100) diamond/Me3” and “Me1/AlN/Me2/(100) diamond/Me3” under three metal film depositions, including the change in the quality factor Q as a result of Me3 impact, were obtained. [...] Read more.

New theoretical and experimental results of microwave acoustic wave propagation in diamond-based multilayer piezoelectric structures (MPS) as “Me1/(Al,Sc)N/Me2/(100) diamond/Me3” and “Me1/AlN/Me2/(100) diamond/Me3” under three metal film depositions, including the change in the quality factor Q as a result of Me3 impact, were obtained. Further development of our earlier studies was motivated by the necessity of creating a sensor model based on the above fifth layered MPS and its in-depth study using the finite element method (FEM). Experimental results on the change in operational checkpoint frequencies and quality factors under the effect of film deposition are in satisfactory accordance with FEM data. The relatively small decrease in the quality factor of diamond-based high overtone bulk acoustic resonator (HBAR) under the metal layer effect observed in a wide microwave band could be qualified as an important result. Changes in operational resonant frequencies vs. film thickness were found to have sufficient distinctions. This fact can be quite explained in terms of the difference between acoustic impedances of diamond and deposited metal films. Full article

(This article belongs to the Special Issue 10th Anniversary of Electronics: Recent Advances in Microelectronics and Optoelectronics)

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12 pages, 1202 KiB

Open AccessFeature PaperArticle

High Frequency Analysis and Optimization of Planar Spiral Inductors Used in Microelectronic Circuits

by Claudia Pacurar, Vasile Topa, Adina Giurgiuman, Calin Munteanu, Claudia Constantinescu, Marian Gliga and Sergiu Andreica

Electronics 2021, 10(23), 2897; https://doi.org/10.3390/electronics10232897 - 23 Nov 2021

Cited by 9 | Viewed by 3473

Abstract

This paper deals with high frequency analysis of spiral inductors, used in microelectronics circuits, to optimize their configuration. Software developed, designed, and implemented by the authors for nano and micrometre spiral inductor high frequency analysis, named ABSIF, is presented in this paper. ABSIF [...] Read more.

This paper deals with high frequency analysis of spiral inductors, used in microelectronics circuits, to optimize their configuration. Software developed, designed, and implemented by the authors for nano and micrometre spiral inductor high frequency analysis, named ABSIF, is presented in this paper. ABSIF determines the inductance, quality factor, and electrical parameters for square, hexagonal, octagonal, and circular spiral inductors and their configuration optimization for energy efficiency. ABSIF is a good tool for spiral inductor design optimization in high frequency applications and takes into account the imposed technological limits and/or the designers’ constraints. A set of spiral inductors are considered and analysed for high frequency values using ABSIF, and the results are presented in the paper. The validation of ABSIF was completed by comparing the results with those obtained using a similar commercial software, Sonnet Lite^TM, which is dedicated to high frequency electromagnetic analysis. Full article

(This article belongs to the Special Issue 10th Anniversary of Electronics: Recent Advances in Microelectronics and Optoelectronics)

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10 pages, 2974 KiB

Open AccessArticle

Gate-Voltage-Modulated Spin Precession in Graphene/WS₂ Field-Effect Transistors

by Amir Muhammad Afzal, Muhammad Farooq Khan and Jonghwa Eom

Electronics 2021, 10(22), 2879; https://doi.org/10.3390/electronics10222879 - 22 Nov 2021

Cited by 9 | Viewed by 2553

Abstract

Transition metal dichalcogenide materials are studied to investigate unexplored research avenues, such as spin transport behavior in 2-dimensional materials due to their strong spin-orbital interaction (SOI) and the proximity effect in van der Waals (vdW) heterostructures. Interfacial interactions between bilayer graphene (BLG) and [...] Read more.

Transition metal dichalcogenide materials are studied to investigate unexplored research avenues, such as spin transport behavior in 2-dimensional materials due to their strong spin-orbital interaction (SOI) and the proximity effect in van der Waals (vdW) heterostructures. Interfacial interactions between bilayer graphene (BLG) and multilayer tungsten disulfide (ML-WS₂) give rise to fascinating properties for the realization of advanced spintronic devices. In this study, a BLG/ML-WS₂ vdW heterostructure spin field-effect transistor (FET) was fabricated to demonstrate the gate modulation of Rashba-type SOI and spin precession angle. The gate modulation of Rashba-type SOI and spin precession has been confirmed using the Hanle measurement. The change in spin precession angle agrees well with the local and non-local signals of the BLG/ML-WS₂ spin FET. The operation of a spin FET in the absence of a magnetic field at room temperature is successfully demonstrated. Full article

(This article belongs to the Special Issue 10th Anniversary of Electronics: Recent Advances in Microelectronics and Optoelectronics)

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6 pages, 1317 KiB

Open AccessFeature PaperArticle

GaN-Based PCSS with High Breakdown Fields

by Matthew Gaddy, Vladimir Kuryatkov, Nicholas Wilson, Andreas Neuber, Richard Ness and Sergey Nikishin

Electronics 2021, 10(13), 1600; https://doi.org/10.3390/electronics10131600 - 3 Jul 2021

Cited by 10 | Viewed by 3188

Abstract

The suitability of GaN PCSSs (photoconductive semiconductor switches) as high voltage switches (>50 kV) was studied using a variety of commercially available semi-insulating GaN wafers as the base material. Analysis revealed that the wafers’ physical properties were noticeably diverse, mainly depending on the [...] Read more.

The suitability of GaN PCSSs (photoconductive semiconductor switches) as high voltage switches (>50 kV) was studied using a variety of commercially available semi-insulating GaN wafers as the base material. Analysis revealed that the wafers’ physical properties were noticeably diverse, mainly depending on the producer. High Voltage PCSSs were fabricated in both vertical and lateral geometry with various contacts, ohmic (Ti/Al/Ni/Au or Ni/Au), with and without a conductive n-GaN or p-type layer grown by metal-organic chemical vapor deposition. Inductively coupled plasma (ICP) reactive ion etching (RIE) was used to form a mesa structure to reduce field enhancements allowing for a higher field to be applied before electrical breakdown. The length of the active region was also varied from a 3 mm gap spacing to a 600 µm gap spacing. The shorter gap spacing supports higher electric fields since the number of macro defects within the device’s active region is reduced. Such defects are common in hydride vapor phase epitaxy grown samples and are likely one of the chief causes for electrical breakdown at field levels below the bulk breakdown field of GaN. Finally, the switching behavior of PCSS devices was tested using a pulsed, high voltage testbed and triggered by an Nd:YAG laser. The best GaN PCSS fabricated using a 600 µm gap spacing, and a mesa structure demonstrated a breakdown field strength as high as ~260 kV/cm. Full article

(This article belongs to the Special Issue 10th Anniversary of Electronics: Recent Advances in Microelectronics and Optoelectronics)

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18 pages, 1311 KiB

Open AccessFeature PaperArticle

Behavioral Model of Silicon Photo-Multipliers Suitable for Transistor-Level Circuit Simulation

by Gianluca Giustolisi, Paolo Finocchiaro, Alfio Pappalardo and Gaetano Palumbo

Electronics 2021, 10(13), 1551; https://doi.org/10.3390/electronics10131551 - 27 Jun 2021

Viewed by 3086

Abstract

Silicon Photomultipliers (SiPMs) are photo-electronic devices able to detect single photons and permit the measurement of weak optical signals. Single-photon detection is accomplished through high-performance read-out front-end electronics whose design needs accurate modeling of the photomultiplier device. In the past, a useful model [...] Read more.

Silicon Photomultipliers (SiPMs) are photo-electronic devices able to detect single photons and permit the measurement of weak optical signals. Single-photon detection is accomplished through high-performance read-out front-end electronics whose design needs accurate modeling of the photomultiplier device. In the past, a useful model was developed, but it is limited to the device electrical characteristic and its parameter extraction procedure requires several measurement steps. A new silicon photomultiplier model is proposed in this paper. It exploits the Verilog-a behavioral language and is appropriate to transistor-level circuit simulations. The photon detection of a single cell is modeled using the traditional electrical model. A statistical model is included to describe the silicon photomultiplier noise caused by dark-count or after-pulsing effects. The paper also includes a procedure for the extraction of the model parameters through measurements. The Verilog-a model and the extraction procedure are validated by comparing simulations to experimental results. Full article

(This article belongs to the Special Issue 10th Anniversary of Electronics: Recent Advances in Microelectronics and Optoelectronics)

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10 pages, 2281 KiB

Open AccessArticle

Accurate Determination of Conversion Gains of SVOM VT CCDs Based on a Signal-Dependent Charge-Sharing Mechanism

by Yue Pan, Xuewu Fan, Hu Wang, Hui Zhao, Yulei Qiu, Wei Gao and Jian Zhang

Electronics 2021, 10(8), 931; https://doi.org/10.3390/electronics10080931 - 14 Apr 2021

Cited by 4 | Viewed by 2394

Abstract

The signal-variance method and the photon transfer curve method are the most valuable tools for calculating the conversion gains of charge-coupled device (CCD) detectors. This paper describes the phenomena that arise in the conversion gain measurements of space multi-band variable object monitor (SVOM) [...] Read more.

The signal-variance method and the photon transfer curve method are the most valuable tools for calculating the conversion gains of charge-coupled device (CCD) detectors. This paper describes the phenomena that arise in the conversion gain measurements of space multi-band variable object monitor (SVOM) visible telescope (VT) CCDs, where the results of the signal-variance method increase with the image gray level, and the results of the photon transfer curve method appear with nonlinearity, which is caused by the signal-dependent charge sharing mechanism of back-illuminated CCDs. A numerical simulation model based on random variables was adopted to analyze the influence of the mechanism on the gain determination. The model simulates all the signals and noise in the flat field image, including the photon signal and photon-shot noise, readout noise, fixed pattern noise, and the signal-dependent charge-sharing signal, and it demonstrated agreement with the experimental data. Then, we proposed a quadratic polynomial curve-fitting formula for the photon transfer curve, and we quantitatively analyzed the relationship between the fitting coefficients and the gain, the signal-dependent charge sharing coefficient, and the full well capacity using the control variable method. Finally, the formula was used to accurately determine the conversion gains of SVOM VT CCDs. Full article

(This article belongs to the Special Issue 10th Anniversary of Electronics: Recent Advances in Microelectronics and Optoelectronics)

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Review

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18 pages, 69053 KiB

Open AccessReview

Actively MEMS-Based Tunable Metamaterials for Advanced and Emerging Applications

by Rui-Jia Xu and Yu-Sheng Lin

Electronics 2022, 11(2), 243; https://doi.org/10.3390/electronics11020243 - 13 Jan 2022

Cited by 47 | Viewed by 6210

Abstract

In recent years, tunable metamaterials have attracted intensive research interest due to their outstanding characteristics, which are dependent on the geometrical dimensions rather than the material composition of the nanostructure. Among tuning approaches, micro-electro-mechanical systems (MEMS) is a well-known technology that mechanically reconfigures [...] Read more.

In recent years, tunable metamaterials have attracted intensive research interest due to their outstanding characteristics, which are dependent on the geometrical dimensions rather than the material composition of the nanostructure. Among tuning approaches, micro-electro-mechanical systems (MEMS) is a well-known technology that mechanically reconfigures the metamaterial unit cells. In this study, the development of MEMS-based metamaterial is reviewed and analyzed based on several types of actuators, including electrothermal, electrostatic, electromagnetic, and stretching actuation mechanisms. The moveable displacement and driving power are the key factors in evaluating the performance of actuators. Therefore, a comparison of actuating methods is offered as a basic guideline for selecting micro-actuators integrated with metamaterial. Additionally, by exploiting electro-mechanical inputs, MEMS-based metamaterials make possible the manipulation of incident electromagnetic waves, including amplitude, frequency, phase, and the polarization state, which enables many implementations of potential applications in optics. In particular, two typical applications of MEMS-based tunable metamaterials are reviewed, i.e., logic operation and sensing. These integrations of MEMS with metamaterial provide a novel route for the enhancement of conventional optical devices and exhibit great potentials in innovative applications, such as intelligent optical networks, invisibility cloaks, photonic signal processing, and so on. Full article

(This article belongs to the Special Issue 10th Anniversary of Electronics: Recent Advances in Microelectronics and Optoelectronics)

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19 pages, 4266 KiB

Open AccessReview

UV-Based Technologies for SARS-CoV2 Inactivation: Status and Perspectives

by Nicola Trivellin, Francesco Piva, Davide Fiorimonte, Matteo Buffolo, Carlo De Santi, Viviana Teresa Orlandi, Fabrizio Dughiero, Gaudenzio Meneghesso, Enrico Zanoni and Matteo Meneghini

Electronics 2021, 10(14), 1703; https://doi.org/10.3390/electronics10141703 - 16 Jul 2021

Cited by 37 | Viewed by 6006

Abstract

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the etiologic agent of COVID-19, which has affected the international healthcare systems since the beginning of 2020. Among sanitizing approaches, UV irradiation is a well-known technology often used in different environments to reduce the microbial [...] Read more.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the etiologic agent of COVID-19, which has affected the international healthcare systems since the beginning of 2020. Among sanitizing approaches, UV irradiation is a well-known technology often used in different environments to reduce the microbial contamination and the viral transmission. In particular, several works have demonstrated that UVC radiation is able to inactivate SARS-CoV-2 compromising its viral genome and virion integrity. With this work we review and analyze the current status of the pandemic and the state of the art of the UV technology. With traditional UVC discharge lamps having a serious environmental issue, due to their working principle based on mercury, a primary focus is shifted on the aluminum gallium nitride based deep-ultraviolet light emitting diodes. These devices are exploited for compact and environmentally friendly disinfection systems, but efficiency and reliability still play a limiting role into their mass market adoption and system efficacy. In this work we then analyze the latest reports on the effects of dose and wavelength on viral inactivation, thus providing two key pillars for the development of UVC based disinfection systems: the status of the technology and a quantitative evaluation of the dose required to achieve an effective coronavirus inactivation. Full article

(This article belongs to the Special Issue 10th Anniversary of Electronics: Recent Advances in Microelectronics and Optoelectronics)

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