Bias Conditions Research Articles

Study of Proton-Induced Defects in 40-nm CMOS SPADs

Defects induced by 62 MeV protons in SPADs are studied. A study of the Dark Count Rate (DCR) variation after irradiations for different biasing conditions underlines the predominance of field enhancement effects such as Poole-Frenkel effect and phonon-assisted-tunneling over band-to-band tunneling. Activation energy measurements below mid-gap value confirm the important contribution of these field effects. However, unexpected behaviors in these energies are seen: very low activation energies are extracted for SPADs with a DCR induced around 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> counts per second. We attribute them to the contribution of different groups of defects, with different energy level distribution. This analysis is completed with an annealing study between 100 °C and 300 °C. Results for high DCR SPADs correlate well with the presence of defect clusters. Moreover, histogram of the annealing temperature at which the DCR starts to drop displays two peaks at 170 °C and 250 °C. The first one is attributed to phosphorus vacancies and complex cluster of defects with an energy distribution inside the Si bandgap centered above mid-gap. The second one is attributed to clusters of divacancies that also anneal at temperatures around 250 °C.

Noise performance of back‐barrier engineered GaN‐based trigate HEMT for X‐band applications

AbstractIn this work, a comprehensive investigation on the noise performance of novel optimized back‐barrier engineered GaN based trigate HEMT (BB‐trigate HEMT), have been carried out using Sentaurus TCAD tool. The microwave‐frequency noise of the device has been analyzed using a Green's function approach, assessing the gate and drain noise spectral densities under different bias conditions such as off‐state, subthreshold state and on‐state condition. More importantly, the G‐R noise component in BB‐trigate HEMT is almost eliminated in comparison to conventional trigate HEMT (C‐trigate HEMT). This is due to use of AlGaN back‐barrier layer (BBL). Subsequently, for the first time, it is reported that the noise parameters such as noise resistance and overall noise figure are drastically reduced to ~22 mΩ and ~0.02 dB respectively at 10 GHz frequency for back‐barrier (BB) trigate HEMT having a scaled gate length of 100 nm. The proposed device shows prominent noise performance than conventional trigate HEMT and thereby, it is highly suitable for designing low noise amplifier for X‐band applications.

Electrically Detected Magnetic Resonance on a Chip (EDMRoC) for Analysis of Thin-Film Silicon Photovoltaics

Electrically detected magnetic resonance (EDMR) is a spectroscopic technique that provides information about the physical properties of materials through the detection of variations in conductivity induced by spin-dependent processes. EDMR has been widely applied to investigate thin-film semiconductor materials in which the presence of defects can induce the current limiting processes. Conventional EDMR measurements are performed on samples with a special geometry that allows the use of a typical electron paramagnetic resonance (EPR) resonator. For such measurements, it is of utmost importance that the geometry of the sample under assessment does not influence the results of the experiment. Here, we present a single-board EPR spectrometer using a chip-integrated, voltage-controlled oscillator (VCO) array as a planar microwave source, whose geometry optimally matches that of a standard EDMR sample, and which greatly facilitates electrical interfacing to the device under assessment. The probehead combined an ultrasensitive transimpedance amplifier (TIA) with a twelve-coil array, VCO-based, single-board EPR spectrometer to permit EDMR-on-a-Chip (EDMRoC) investigations. EDMRoC measurements were performed at room temperature on a thin-film hydrogenated amorphous silicon (a-Si:H) pin solar cell under dark and forward bias conditions, and the recombination current driven by the a-Si:H dangling bonds (db) was detected. These experiments serve as a proof of concept for a new generation of small and versatile spectrometers that allow in situ and operando EDMR experiments.

Improved self-heating extraction with RF technique at cryogenic temperatures

This work studies self-heating effect using the modified RF characterization technique at cryogenic temperatures down to 77 K. It is shown that neglecting the transition related to the substrate effect in the output conductance frequency response can result in a strong underestimation of the thermal resistance, especially at bias conditions close to the threshold voltage (Vth) region and alter its temperature, length and bias dependencies which is important to consider for device modelling.

A compact Ka‐band MMIC power amplifier using continuous Class‐B/J mode technique

AbstractThis letter presents a Ka‐band GaAs broadband high efficiency power amplifier (PA). The power amplifier achieves the best trade‐off among gain, output power, power added efficiency (PAE), and fractional bandwidth through nonlinear simulations to select proper device size and bias conditions. The high‐efficiency and broadband performances are achieved by using continuous Class‐B/J mode for fundamental and second harmonics output matching network. The fabricated PA achieves a power gain of 18.8 dB, a 3‐dB bandwidth of 25–30.2 GHz, a saturation power 25.5 dBm, a peak PAE of 30.0%. The chip size is as compact as 1.08 mm2 including all pads.

New Methodology for Parasitic Resistance Extraction and Capacitance Correction in RF AlGaN/GaN High Electron Mobility Transistors

This paper presents a novel approach to the efficient extraction of parasitic resistances in high electron mobility transistors (HEMTs). The study reveals that the gate resistance value can be accurately determined under specific forward gate bias conditions (Vg = 1.0 V), although the gate resistance value becomes unreliable beyond this threshold (Vg &gt; 1.0 V) due to potential damage to the Schottky contact. Furthermore, by examining the characteristics of the device under a cold-FET bias condition (Vds = 0 V), a linear correlation between the gate and drain current is identified, enabling an estimation of the interdependence between the drain and source resistance using the proposed method. The estimation of parasitic pad capacitance (Cpg and Cpd) from Dambrine’s model is refined by incorporating the depletion layer capacitance on the gate side during the pinch-off condition. To validate the accuracy of the extracted parasitic capacitance and resistance values obtained from the new method, small-signal modeling is performed on a diverse range of measured devices.

Tunable non-reciprocal waveguide using spoof plasmon polariton coupling to a gaseous magnetoplasmon.

We experimentally demonstrate non-reciprocal (one-way) waveguiding in a microstrip transmission line tailored to support the propagation of spoof plasmon polaritons. Time-reversal symmetry is broken by coupling the microstrip fields to a magnetized gaseous plasma discharge column thereby exciting non-reciprocal magnetoplasmons at the interface between the plasma and a surrounding quartz envelope. The magnetic bias introduces asymmetry in the dispersion of the surface plasmon polaritons at the gaseous plasma-dielectric interface, resulting in a breaking of the bidirectionality of the wave propagation in the microstrip. The isolation generated at conditions of modest magnetic bias is measured to be nearly 60 dB, and tunable by varying the plasma density through the voltage applied to the discharge. The advantage of using magnetized gaseous plasmas to produce this unidirectional waveguide structure is that it can be turned on or off at rates limited by the production and recombination of the plasma.

Study of Low Noise with High Linearity AlGaN/GaN HEMTs by Optimizing Γ-Gate Structure for Ka-Band Applications

This paper investigates the device noise and linearity of an AlGaN/GaN HEMT with an optimized Γ-Gate structure for Ka-band applications. The Γ-Gate was used to provide low gate resistance for the device by increasing the gate cross-section and acting as a gate field plate to achieve a flat transconductance (Gm) profile. The device’s Gm profile was analyzed under different gate positions, including at the center or close to the source. Under different bias conditions, we performed the optimization of the Γ-gate head length (Lhead). The results show that an excellent minimum noise figure (NFmin) for the device can be achieved when the Γ-gate is positioned close to the source with an optimum Lhead. Finally, the NFmin improved from 1.9 dB to 1.59 dB and the third-order intercept point (OIP3) value improved from 27.7 dBm to 31.1 dBm when the source-drain distance (LSD) was reduced from to It was demonstrated that the optimized Γ-Gate design has the potential to attain the device with low noise and high linearity.

A spectrally selective self-powered photodetector utilizing a ZnO/Cu2O heterojunction

Most heterojunction photodetectors (PDs) can detect single-band, dual-band, or even multi-band light. However, the ability to adjust the spectral response band of the PD remains a challenge. This study presents a self-powered PD based on a ZnO/Cu2O heterojunction that overcomes this limitation. Adjustable and selective detection bands were achieved within a single device by controlling the direction of the incident light. Under zero bias conditions, the PD exhibits a response exclusively in the 500–750 nm region when the light is incident from the ZnO side, with a responsivity of 1.27 mA W−1. Conversely, when the light is incident from the Cu2O side, responsivities of 10.63 and 52.42 mA W−1 are achieved in the 275–750 nm region. Remarkably, the ZnO/Cu2O PD enables tunable detection of the response region depending on the incident light direction. The dual-band response is attributed to the differential distribution of the width of the depletion layer and the built-in electric field. This study offers valuable insights into the potential applications of PDs with spectral selectivity in optical communication, sensing, and intelligent optoelectronic devices.

Fast transition-edge sensors suitable for photonic quantum computing

Photon-number resolving transition-edge sensors (TESs) with near unity system detection efficiency enable novel approaches to quantum computing, for example, heralding robust Gottesman–Kitaev–Preskill qubit states. Increasing the speed of the detectors increases the rate at which these states can be heralded. In addition, depending on the details of the scheme, faster detectors can reduce the complexities of the hardware implementation. In previous work, we demonstrated that adding a small amount of gold between the tungsten film and silicon substrate can increase thermal conductance and reduce detector recovery time. In that study, the readout electronics imposed limitations on stable biasing conditions of the TES detector, and the TES could only be biased at higher than ideal values. In this report, we demonstrate the operation of the TES illuminated by a heavily attenuated pulsed laser running at 1 MHz repetition rate and examine the limits to adding gold to speed up device recovery times using a higher bandwidth readout system. The best performance was achieved by combining a 15×15μm2 tungsten TES with 5μm3 of gold, which resulted in a recovery time faster than 250 ns, with an energy resolution of 0.25 eV full-width at half maximum at 0.8 eV photon energy.

Room Temperature Bias-Selectable, Dual-Band Infrared Detectors Based on Lead Sulfide Colloidal Quantum Dots and Black Phosphorus

A single photodetector capable of switching its peak spectral photoresponse between two wavelength bands is highly useful, particularly for the infrared (IR) bands in applications such as remote sensing, object identification, and chemical sensing. Technologies exist for achieving dual-band IR detection with bulk III–V and II–VI materials, but the high cost and complexity as well as the necessity for active cooling associated with some of these technologies preclude their widespread adoption. In this study, we leverage the advantages of low-dimensional materials to demonstrate a bias-selectable dual-band IR detector that operates at room temperature by using lead sulfide colloidal quantum dots and black phosphorus nanosheets. By switching between zero and forward bias, these detectors switch peak photosensitive ranges between the mid- and short-wave IR bands with room temperature detectivities of 5 × 109 and 1.6 × 1011 cm Hz1/2 W–1, respectively. To the best of our knowledge, these are the highest reported room temperature values for low-dimensional material dual-band IR detectors to date. Unlike conventional bias-selectable detectors, which utilize a set of back-to-back photodiodes, we demonstrate that under zero/forward bias conditions the device’s operation mode instead changes between a photodiode and a phototransistor, allowing additional functionalities that the conventional structure cannot provide.

The Interplay Effects between Feed-Gas Composition and Bias Plasma Condition during Active-Screen Plasma Nitrocarburizing with a Solid Carbon Source

Recent technological development of utilizing an active screen made of solid carbon for plasma-assisted thermochemical diffusion treatments opens up new possibilities for control over the in situ generated treatment environment to guarantee reproducible treatment conditions and material responses. Until now, the investigations of active-screen plasma nitrocarburizing (ASPNC) using an active screen manufactured from solid carbon focused on the influence of a single treatment parameter variation on the material response. In this systematic study, experiments were conducted to vary the H2-N2 feed-gas composition while varying the bias plasma power. The experiments served to better understand a simultaneous variation in the mentioned parameters on the resulting treatment environment and material response during ASPNC of AISI 316L austenitic stainless steel. Therefore, nitriding and carburizing effects in the expanded austenite layer can be obtained. It is shown that an increased nitriding effect, i.e., nitrogen diffusion depth and content, was achieved in case of biased conditions and for H2-N2 feed-gas compositions with higher N2 amounts. On the contrary, an increased carburizing effect, i.e., carbon diffusion depth and content, was achieved in nonbiased conditions, independent from the H2-N2 feed-gas composition.

Harmonic and DC Bias Hysteresis Characteristics Simulation Based on an Improved Preisach Model.

Transformers, reactors and other electrical equipment often work under harmonics and DC-bias working conditions. It is necessary to quickly and accurately simulate the hysteresis characteristics of soft magnetic materials under various excitation conditions in order to achieve accurate calculations of core loss and the optimal design of electrical equipment. Based on Preisach hysteresis model, a parameter identification method for asymmetric hysteresis loop simulation is designed and applied to the simulation of hysteresis characteristics under bias conditions of oriented silicon steel sheets. In this paper, the limiting hysteresis loops of oriented silicon steel sheets are obtained through experiments under different working conditions. The first-order reversal curves(FORCs) with asymmetric characteristics is generated numerically, and then the Everett function is established under different DC bias conditions. The hysteresis characteristics of the oriented silicon steel sheets under harmonics and DC bias are simulated by improving FORCs identification method of the Preisach model. By comparing the results of simulation and experiment, the effectiveness of the proposed method is verified, so as to provide an important reference for material production and application.

Design of 2.45-GHz High-Efficiency Miniaturized Power Oscillator Using GaN HEMT

This study presents a method for designing a highly efficient miniaturized power oscillator with gallium nitride high electron mobility transistor (GaN HEMT). A harmonic-tuning highly efficient power amplifier (PA) using GaN HEMT is designed firstly by finding optimal fundamental, 2nd and 3rd harmonic load impedances. After the performance of PA meets the requirements, the feedback circuit that is made of a hairpin resonator and a coupler is studied based on the power gain of PA and the required frequency. Both the size of the PA and the feedback circuit should be taken into account to minimize the oscillator at last. Finally, the PA and feedback circuit are combined into a power oscillator. Through this way, the highly efficient miniaturized power oscillator with a size of 2.7*4.9 cm2 fabricated on substrate of FR4 outputs 37.7 dBm power and 72% efficiency at 2.4518 GHz under the bias condition of Vgs = - 3.21V, Vds = 28V, Ids = 25mA.

Nanomanipulation of Functionalized Gold Nanoparticles on GaN

Gold nanoparticles (AuNPs) is known for its high surface area to volume ratio which acts as an excellent receptor when placed in between electrodes in sensors application. Microelectrodes which are bar and needle shape pointed ends with two arrangements; comb and castle wall configurations were designed to be used for fabrication of electrodes to observe the relation between geometry of electrodes and dielectrophoretic of AuNPs on p-gallium nitride (GaN) substrates. The dielectrophoretic behaviour and electrical properties were analysed before and after the drop cast of AuNPs using current-voltage (I-V) curve method with manual probing. Resistance values of each sample were calculated under reverse bias condition. The effect of design on the nanomanipulation of AuNPs will be discussed.

Impact of Temperature on Neutron Irradiation Failure-in-Time of Silicon and Silicon Carbide Power MOSFETs

Accelerated neutron tests on silicon (Si) and silicon carbide (SiC) power MOSFETs at different temperatures and drain bias voltages were performed at the ChipIr facility (Didcot, UK). A super-junction silicon MOSFET and planar SiC MOSFETs with different technologies made by STMicroelectronics were used. Different test methods were employed to investigate the effects of temperature on neutron susceptibility in power MOSFETs. The destructive tests showed that all investigated devices failed via a single-event burnout (SEB) mechanism. Non-destructive tests conducted by using the power MOSFET as a neutron detector allowed measuring the temperature trend of the deposited charge due to neutron interactions. The results of the destructive tests, in the −50 °C–180 °C temperature range, revealed the lack of a common trend concerning the FIT temperature dependence among the investigated SiC power MOSFETs. Moreover, for some test vehicles, the FIT-temperature curves were dependent on the bias condition. The temperature dependence of the FIT values, observed in some SiC devices, is weaker with respect to that measured in the Si MOSFET. The results of the non-destructive tests showed a good correlation between the temperature trends of the deposited charge with those of FIT data, for both Si and SiC devices.

Self-biased and biased photo-sensitivity of Tin Mono-Selenide (SnSe) photonic crystal Photodetector under poly/monochromatic light

Recently, transition metal chalcogenides were found to be the most promising candidates for photosensor- and photodetector-based applications. This study reports the photodetection and response properties of tin selenide (SnSe) crystals grown by the direct vapour transport (DVT) technique. The basic properties of SnSe have been reported in a previous article. Photodetection properties are investigated using polychromatic or monochromatic light of varying intensities and bias voltages. Results depict that detectors work congenially under monochromatic sources of light. It is observed that responsivity (Rλ) is higher for red, while detectivity and sensitivity are observed to be maximum for blue light under the self-biased (no bias) condition. The results observed under varying intensity (spot size) in the absence of biassing suggest that as intensity rises, all the parameters of the photodetector are also rising, while at constant intensity (30 mW/cm2), by varying the bias voltage, the detectivity of red light is decreasing due to an increment in dark current. Photodetectors are more efficient at converting optical signals to electrical signals, and their sensitivity is colour-dependent. Mainly, it is observed that monochromatic light shows high sensitivity to low bias voltages, while polychromatic light shows high sensitivity to high voltages. Observed results point to the detection of both monochromatic and polychromatic light by the fabricated detector, which can be applied to SnSe-based devices. A device can be used to fabricate colour and intensity detection.

Work flux and efficiency at maximum power of a triply squeezed engine

We explore the effects of quantum mechanical squeezing on the nonequilibrium thermodynamics of a coherent heat engine with squeezed reservoirs coupled to a squeezed cavity. We observe that the standard known phenomenon of flux optimization beyond the classical limit with respect to quantum coherence is destroyed as the cavity is squeezed. This loss is independent of reservoir squeezing. Under biased conditions, the squeezing-dependent flux is always higher than the classical limit. The efficiency at maximum power (EMP) in the presence of cavity-squeezing is greater than what was predicted by Curzon and Ahlborn even in the absence of reservoir squeezing. The EMP with respect to either reservoir's squeezing parameters is surprisingly equal and linear in ${\ensuremath{\eta}}_{C}$ with a slope unequal to the universally accepted slope, $1/2$. The slope is found to be proportional to the dissipation into the cavity mode with an intercept proportional to a specific numerical value of the engine's efficiency.

Self-Powered Broadband Photodetectors Material Based on Co3O4–ZnO Heterojunction with Bottlebrush Nanostructure

Self-powered broadband photodetectors operating in the ultraviolet–visible window are essential for optical communication, military monitoring, multispectral detection, and environmental monitoring. In this study, a new bottlebrush nanostructure based on the Co3O4–ZnO PN junction is fabricated as an efficient broadband photodetector capable of operation under zero bias conditions. This photodetector has a reasonable band structure, exhibits improved efficiency of light absorption, and features reduced electron–hole recombination. Moreover, the device exhibits highly efficient detection performance in the UV–visible region. The responsivity (R), specific detectivity (D), and response speed of the device were 22.7 mA W–1, 3.14 × 1012 Jones, and 20/90 ms, respectively. These results suggest a new strategy for fabricating broadband photodetectors based on stable, nontoxic, low-cost metal oxides.

In-plane mixed-dimensional 2D/2D/1D MoS2/MoTe2/Mo6Te6 heterostructures for low contact resistance optoelectronics

Mixed-dimensional heterostructures formed by combining 2D materials and other dimensional (0D, 1D, and 3D) materials provide new opportunities for various applications owing to their novel properties. However, in-plane mixed-dimensional heterostructures have been rarely investigated. Here, we report a novel flux-controlled chemical vapor deposition method for synthesizing in-plane mixed-dimensional heterostructures composed of monolayer MoS2 and low-dimensional Mo/Te compounds. By adjusting the Te flux and growth time, we controlled the composition, dimension, and phase of the Mo/Te compounds interfaced with the MoS2. While in-plane 2D/1D MoS2/Mo6Te6 and 2D/2D/1D MoS2/2H MoTe2/Mo6Te6 heterostructures were obtained with a low Te flux, in-plane 2D/2D MoS2/mixed 2H-1T’ MoTe2 and 2D/2D MoS2/2H MoTe2 heterostructures were synthesized with a high Te flux. We investigated the transport properties of the devices fabricated with in-plane mixed-dimensional 2D/2D/1D MoS2/2H MoTe2/Mo6Te6 heterostructures and imaged localized electronic band structures using scanning photocurrent microscopy. Under the low bias condition, the device exhibited an Ohmic-like behavior, which has not been achieved in conventional devices with stacked van der Waals junctions. Under the high bias condition, the device showed a rectifying behavior because of band-bending formed at the heterojunctions; this is consistent with the electronic band-alignment expected from the bandgap and electron affinity of the materials.