Bias Conditions Research Articles

Michael is better than Mehmet: exploring the perils of algorithmic biases and selective adherence to advice from automated decision support systems in hiring.

Artificial intelligence algorithms are increasingly adopted as decisional aides in many contexts such as human resources, often with the promise of being fast, efficient, and even capable of overcoming biases of human decision-makers. Simultaneously, this promise of objectivity and the increasing supervisory role of humans may make it more likely for existing biases in algorithms to be overlooked, as humans are prone to over-rely on such automated systems. This study therefore aims to investigate such reliance on biased algorithmic advice in a hiring context. Simulating the algorithmic pre-selection of applicants we confronted participants with biased or non-biased recommendations in a 1 × 2 between-subjects online experiment (n = 260). The findings suggest that the algorithmic bias went unnoticed for about 60% of the participants in the bias condition when explicitly asking for this. However, overall individuals relied less on biased algorithms making more changes to the algorithmic scores. Reduced reliance on the algorithms led to the increased noticing of the bias. The biased recommendations did not lower general attitudes toward algorithms but only evaluations for this specific hiring algorithm, while explicitly noticing the bias affected both. Individuals with a more negative attitude toward decision subjects were more likely to not notice the bias. This study extends the literature by examining the interplay of (biased) human operators and biased algorithmic decision support systems to highlight the potential negative impacts of such automation for vulnerable and disadvantaged individuals.

On analysis of structural and optical absorption characterization of Bi35Sb5Se60 nanostructured thin films for photosensing application

In this extensive study, the primary focus is directed towards the intricate exploration of the optical absorption characteristics inherent in nanostructured Bi35Sb5Se60 thin films, prepared by thermal evaporation under a vacuum of 10−5 Torr, ensuring high purity and uniformity for optoelectronic applications. With a particular emphasis on their prospective application in photosensing devices. The research employs a comprehensive approach, integrating various spectrophotometric measurements that encompass both transmission and reflection analyses. The meticulous examination of the absorption edge characteristics reveals a direct energy gap of 1.82 eV, providing a foundational understanding of the material's electronic structure. The determination of the dispersion energy at 6.35 eV and the oscillator energy at 2.96 eV further enriches the understanding of the material's optical behavior, shedding light on its capacity to interact with incident light. A noteworthy highlight emerges with the identification of high photosensitivity exhibited by the heterojunction, particularly under lower reverse bias conditions, underscoring its potential utility in photosensing applications. The PL spectra reveal a highly broadened defect emission band with peaks at 475 nm, 490 nm, and 540 nm, providing insights into the recombination processes within the material. The identification of emission peaks related to the conduction band edge and acceptor levels further enhances the comprehension of the material's optical and electronic characteristics. underscores the potential of these nanostructured thin films for efficient photosensing devices. The findings presented in this research not only advance the understanding of the material's properties but also lay a robust foundation for further research and development in the design and optimization of photoresponsive devices within the realm of optoelectronic technologies.

The Mechanism of Current Transfer in n-GaAs – p(ZnSe)1-x-y(Ge2)x(GaAs1–δBiδ)y Heterostructures

The I-V characteristics of heterostructures n-GaAs – p-(ZnSe)1–x–y(Ge2)x(GaAs1–δBiδ) exhibit a characteristic quadratic law - J~V2 I-V curve, followed by a sharp pre-breakdown current growth, which well explains the observed straight branch of the I-V characteristics and this regularity remains unchanged at different temperatures. The analysis of the I-V characteristics of n‑GaAs‑p‑(ZnSe)1‑x‑y(Ge2)x(GaAs1–δBiδ) heterostructures with an extended intermediate solid solution layer shows that the drift mechanism of charge transport predominates under forward bias conditions.

Localized Surface Modification during Alternating Current Scanning Electrochemical Microscopy: Origin and Mechanism

In the current study, we report for the first time the observation of unintended localized surface modification on commercially pure aluminum (Al) during an alternating current scanning electrochemical microscopy (AC-SECM) analysis, its origin, and the probable mechanism responsible for it. Application of an AC perturbation potential (∼100 mV amplitude at ∼100 kHz frequency) to the Platinum ultramicroelectrode (Pt UME), during AC-SECM in acidic, neutral chloride, tap water, and alkaline electrolytes was found to cause surface modification on the scanned region of Al. An increase in the local pH of the electrolyte between the UME and the Al substrate, irrespective of the electrolyte pH (3–11) and UME biasing conditions, led to the local surface modification. The reason for the enhancement of local pH is attributed to the occurrence of higher rates of cathodic reduction reactions than that of anodic oxidation reactions. The reduction of dissolved oxygen/protons/water in the electrolytes led to the generation or consumption of OH−/H+ ions, respectively, and thus increased the pH, whereas the oxidation of Pt UME/Al surfaces decreased the pH with the generation of H+ or consumption of OH− ions. These results contribute significantly to accurately analyzing Al and its alloys using the AC-SECM technique.

The Impact of Gamma Irradiation on 4H-SiC Bipolar Junction Inverters under Various Biasing Conditions

In this study, we introduce the impact of gamma irradiation on 4H-SiC based transistor-transistor logic (TTL) inverters. These monolithic bipolar inverters have been successfully demonstrated in a broad spectrum of temperature and supply voltage conditions. In this iteration of experiments, attempts made to the processing to increase beta values. The gamma radiation tests from a 60Co source were conducted under various operation conditions and measured in-situ under different biasing conditions. The Silicon Carbide Integrated circuits ( SiC ICs) show excellent tolerance properties to gamma radiation up to doses of nearly 1 MRad. Comparable Si BJT-based TTL inverters show considerable degradation already at one order of magnitude lower doses, clearly demonstrating the superior radiation hardness of 4H-SiC ICs.

A Unique Failure Mode of SiC MOSFETs under Accelerated HTRB

Device lifetime under reverse bias conditions is an important reliability concern for SiC devices. Provided that the termination structure is well designed, device failure in the active cell is driven by gate oxide breakdown due to the high field in the semiconductor and gate dielectric. For planar MOSFETs, the largest field occurs in the JFET region [1,2]. Standard HTRB testing is insufficient to estimate failure rates under operating conditions and hence testing under accelerated off-state conditions (ALT-HTRB) is required. This paper provides data, statistical analysis, failure analysis and finally a Weibull statistics-based temperature, Vd and stress time dependent model.

Single Event Effects in 3.3 kV 4H-SiC MOSFETs due to MeV Ion Impact

In this work, MeV alpha particles generated from an accelerator are used to study single event breakdown (SEB) in 4H-SiC MOSFET samples, rated at 3.3 kV. The samples are exposed to bursts of alpha particles under reverse bias conditions to investigate the SEB sensitivity to ion energy and reverse bias. The energies of alpha particles are chosen to reach different depths in the drift region of the MOSFET devices, and also to penetrate the whole drift region. Forward and reverse characteristics are measured after each exposure, as long as no failures occur, to ensure that the device performance is maintained. The measurements show that no significant effects are observed on the drain-source leakage current, while minor effects on gate behavior can be seen as a function of accumulated fluence. Furthermore, SEB can only be triggered with a reverse bias larger than, or equal to 3 kV. A standard MOSFET cell with a similar rated voltage is also simulated in Sentaurus TCAD to study these effects, using two different models for the incident ion-induced ionization: the Alpha Particle and the Heavy Ion model. Simulations show that the Alpha Particle model cannot induce any device failures even with a 3.5 kV reverse bias, while it is possible to trigger a failure by the Heavy Ion model, where the ionization can be selected. Carrier plasma and internal electric field distributions of the two models are plotted and compared, showing that device failures triggered by a heavy ion are related to the hole injection at epi-substrate interface, in which linear energy transfer (LET) of the particle plays an important role.

Bolometric detection of Josephson radiation.

One of the most promising approaches towards large-scale quantum computation uses devices based on many Josephson junctions. Yet, even today, open questions regarding the single junction remain unsolved, such as the detailed understanding of the quantum phase transitions, the coupling of the Josephson junction to the environment or how to improve the coherence of a superconducting qubit. Here we design and build an engineered on-chip reservoir connected to a Josephson junction that acts as an efficient bolometer for detecting the Josephson radiation under non-equilibrium, that is, biased conditions. The bolometer converts the a.c. Josephson current at microwave frequencies up to about 100 GHz into a temperature rise measured by d.c. thermometry. A circuit model based on realistic parameter values captures both the current-voltage characteristics and the measured power quantitatively. The present experiment demonstrates an efficient, wide-band, thermal detection scheme of microwave photons and provides a sensitive detector of Josephson dynamics beyond the standard conductance measurements.

A computational analysis of the impact of thin undoped channels in surface-related current collapse of AlGaN/GaN HEMTs

Abstract This study provides an insight into the impact of thin purely undoped GaN channel thickness (t ch) on surface-related trapping effects in AlGaN/GaN high electron mobility transistors. Our TCAD study suggests that in cases where parasitic gate leakage is the driving trapping mechanism that promotes the injection of electrons from the Schottky gate contact into surface states, this effect can be alleviated by reducing t ch of the undoped GaN channel. We show that by decreasing t ch from 130 to 10 nm, devices exhibit a reduction in gate-related current collapse under the specific class-B RF operating bias conditions as a consequence of a substantial decrease in the off-state gate leakage with reducing t ch. Large-signal simulations revealed an increase by 3 W mm−1 and about 12% output power and power-added efficiency due to the decrease of gate-related collapse. This work, for the first time, highlights the role of a proper purely undoped GaN t ch selection to alleviate gate-related surface trapping in the design of GaN-based microwave power amplifiers.

Study on the properties of solar cell under bias condition by using impedance spectroscopy

Study on the properties of solar cell under bias condition by using impedance spectroscopy

Revealing Enhanced Optoelectronic Performance of Sb2Se3‐Based Self‐Sustaining Heterostructures with Bi2Se3 and ZnSe: A Dual Polarity Photo Response

AbstractThrough precise band engineering, Van der Waals heterostructures integration holds great promise for advancing high‐performance optoelectronic devices, especially photodetectors. This study presents self‐sustaining, dual‐polarity, high photo‐responsive heterostrutures (HS) photodetectors based on Sb2Se3, specifically Bi2Se3/Sb2Se3 and ZnSe/Sb2Se3. The Bi2Se3 (ZnSe) layer functions as a channel in a reconfigurable HS phototransistor configuration. These HS devices demonstrate a negative photoconductive response with bias‐modulated polarity switching of the photocurrent. The Bi2Se3/Sb2Se3 device exhibits a responsivity switch from −4 mA W−1 to 0.14 A W−1, while the ZnSe/Sb2Se3 device shows a substantially enhanced responsivity switch from ‐400 mA W−1 to 12 A W−1. This negative photo response results from a photoinduced carrier trapping mechanism at the interface of the channel layer and photosensitizer material. The bias modulation enables the switching from negative to positive responsivity. A comprehensive investigation of photoconductivity modulation provides a deeper understanding of the impact of the photogating effect and trap states under applied bias conditions. Ultrafast transient spectroscopy supports these findings, offering insights into the dynamics of charge carrier relaxation mechanisms and the trapping of photoexcited carriers in defect states, crucial for explaining the dual polarity photo response. These devices present significant advantages for switchable light imaging, optical communication, memory devices, convolution processing, and logic circuits.

Intensity noise reduction in quantum dot comb laser by lower external carrier fluctuations.

This work investigates the impact of carrier noise induced by an external current source on the linewidth enhancement factor (LEF) and relative intensity noise (RIN) of a 100 GHz quantum dot fourth-order colliding-pulse mode-locked laser (MLL), driven by a normal pump with Gaussian-distributed carrier sequences and a quiet pump with sub-Poissonian-distributed carrier sequences. The results indicate that under a normal pump, the LEFs are approximately zero for reverse saturable absorber (SA) bias voltages ranging from 0 to 2.5 V, and the laser achieves a RIN as low as -156 dB/Hz. When using a quiet pump, both the LEF and RIN are reduced across all SA bias conditions, particularly at low reverse SA bias voltages. Specifically, the LEF decreases by up to 0.58 at 0 V, and the average RIN spectrum is reduced by more than 3 dB at the same voltage. This work provides a straightforward approach for the development and optimization of multi-channel light sources for dense wavelength division multiplexing (DWDM) technologies with low optical noise.

(Invited) Analysis of Hysteresis in OTFTs Using a Physically-Based Compact Model

Organic TFTs (OTFs) have the potential to become essential devices for flexible, wearable and printed electronics. However, several issues related to their behavior still needs to be studied in detail and completely understood. One of these issues is hysteresis. In this abstract we analyze the hysteresis behavior in OTFT by applying a previously developed physically-based model to the direct (forward) and reverse (backward) dc sweeps of the transfer characteristics at different drain voltages. The identification of the model parameters which change provides more information about the hysteresis mechanism.The so-called UMEM (unified model and extraction method) model [1,2] developed for OTFT has been demonstrated to accurately reproduce the I-V characteristics for a wide range of geometries, bias and temperature conditions [3], as well as to extract physical values of most parameters. In this work we will show that it can reproduce the post-hysteresis I-V-characteristics of OTFT and that only a few parameters need to be changed.In the above threshold regime, where Variable Range Hopping dominates, the current is proportional to a field-effect mobility μFET= μ0(VGS-VT)γ/VAA γ , being VT the threshold voltage. The γ parameter depends on the DOS characteristic temperature T0 as = 2(T0/T-1).In the subthreshold regime diffusion dominates and the current is exponentially dependent on VGS:IDS=IDS0 exp (2.3(VGS-VT)/S) (1-exp(-VDS/Vth))where S is the subthreshold swing and Vth the thermal voltage.Aunified model of the drain current, valid and continuous from subthreshold to the above threshold regime, is finally obtained by means of a hyperbolic tangent function [1,2].In order to analyze the hysteresis behavior, this model was applied to both direct and reverse dc sweeps of the I-V characteristics of OTFT samples fabricated at CEA-Liten (Grenoble). Figs. 1 and 2 shows very good agreement from subthreshold toabove threshold. The parameter values extracted for the direct and reverse dc sweeps are shown in Table I. It is observed that the threshold voltage is shifted. The increase of γ indicates a higher degree of disorder in the reverse dc sweep characteristics. However, we can see that although IDS0 is higher, the extracted subthreshold swing value, S, does not change. The saturation parameter α is lower in the reverse sweep, but the rest of model parameters are not affected. Only γ and α show a variation with VDS, although rather small.[1] B. Iñiguez, et al., "New Compact Modeling Solutions for Organic and Amorphous Oxide TFTs," IEEE Journal of the Electron Devices Society, vol. 9, pp. 911-932, September 2021[2] C. H. Kim, et al., , “A Compact Model for Organic Field-Effect Transistors With Improved Output Asymptotic Behaviors,”IEEE Trans. on Electron Devices, vol. 60, no. 3, pp. 1136-1141, March 2013.[3] H. Cortés-Ordóñez, et al., “Parameter extraction and compact modeling of OTFT from 150 to 350K,”, Trans. on Electron Devices, vol. 67, no. 12, pp.5695-5692, Dec 2020.Acknowledgements:This work was funded by the Spanish Ministry of Science (PRX21/00726), and the EU EIC-PATHFINDER (BAYFLEX, no 101099555 Figure 1

Phase‐Pure Iron Pyrite Nanocrystals as Air‐Stable Hole‐Transport Materials for Low‐Cost Perovskite Solar Cells

Spiro‐OMeTAD is a commonly used organic hole‐transport material (HTM) in MAPbI3‐based perovskite solar cells (PSCs) for achieving high efficiency. However, its hydrophilic nature compromises device stability and performance reproducibility, especially under ambient conditions. In this study, PSCs are fabricated under ambient conditions, and phase‐pure iron pyrite nanocrystals (FeS2 NCs) are synthesized and utilized as HTM. Using iron pyrite as the HTM leads to a 22% increase in device short‐circuit current density (JSC) compared to Spiro‐OMeTAD, resulting in enhanced PSC performance. This confirms FeS2 NCs as a promising HTM for PSCs. Iron pyrite improves the extraction of photogenerated charge carriers compared to Spiro‐OMeTAD, indicating a superior extraction layer. Furthermore, the longer stability of the iron pyrite layer under humid conditions is compared to the Spiro‐OMeTAD layer, as demonstrated by contact angle measurements. This improvement helps prevent humidity‐induced degradation of the perovskite layer. Transient photocurrent studies under reverse bias conditions reveal fewer defects at the perovskite/iron pyrite interface, suggesting a defect passivation effect of FeS2 NCs. This study demonstrates that iron pyrite can serve as an effective HTM to enhance the performance and stability of low‐cost PSCs fabricated under ambient conditions.

Non-equilibrium excited-state fractionally quantized Hall effects observed via current bias spectroscopy

Studies of fractional quantum Hall effects (FQHE) across various two-dimensional electronic systems (2DES) have helped to establish the equilibrium FQHE many-body ground states with fractionally charged excitations and composite particles in condensed matter. Then, the question arises whether an FQHE system driven to non-equilibrium can approach a different stationary state from the known equilibrium FQHE states. To investigate this question, we examine FQHE over filling factors, ν, 2 ≥ ν ≥ 1 under non-equilibrium finite bias conditions realized with a supplementary dc-current bias, IDC, in high mobility GaAs/AlGaAs devices. Here, we show that all observable canonical equilibrium FQHE resistance minima at ∣IDC∣ = 0 undergo bimodal splitting vs. IDC, yielding branch-pairs and diamond shapes in color plots of the diagonal resistance, as canonical FQHE are replaced, with increasing IDC, by excited-state fractionally quantized Hall effects at branch intersections. A tunneling model serves to interpret the results.

Impedance dynamics in tandem solar cells based on c-Si with upper layers of CsPbBr3 (CsPbI3) perovskite nanocrystals

The application of an additional nanoparticle layer is a common practice for enhancing the optical and electrical properties of third-generation solar cells. In this study, we present the results of impedance spectroscopy (IS) for modified solar cells using Nyquist and Bode diagrams. The structure investigated consists of a conventional double junction based on crystalline silicon (c-Si) coated with thin films of inorganic perovskite nanocrystals (NC) of lead halides CsPbI3 and CsPbBr3. The latter are characterized by a significant phonon disorder, which leads to unique electron-phonon interactions and dielectric responses. The IS results indicate that, under the same conditions, the measured Nyquist plots align well with the simulated ones. An equivalent circuit model is proposed, featuring ohmic resistance, recombination resistance, and geometric capacitance. These elements arise due to charge accumulation, charge transfer resistance, and/or additional interfacial electronic states. The study finds that the introduction of a CsPbI3 layer enhances the photoresponse under bias conditions, but this photoresponse leads to a decrease in DC conductivity. In contrast, the addition of a CsPbBr3 layer obstructs the photoresponse under bias while slightly improving the photoresponse in the absence of an applied voltage. The results obtained contribute to the improvement of tandem solar cell characteristics featuring top layers of perovskite nanocrystals.

Coupling dynamics of locally active memristor based neurons.

Brain-like dynamics require third-order or higher-order complexity. In order to investigate the coupling neuromorphic behaviors of identical third-order memristive neurons, this paper begins with the aim of exploring two identical neuron based dynamics under distinct operating regimes and coupling strengths. Without coupling, the single neuron can exhibit resting states, periodic spikes, or chaos depending on the bias condition. The uncoupled resting neurons can be activated by resistive coupling, inducing inhomogeneous resting states (static Smale paradox) and inhomogeneous spikes (dynamic Smale paradox) due to the edge of chaos regime. Considering the single neuron at the periodic spikes or chaotic states, the coupled neurons can mimic shocking oscillation death, non-periodic asynchronization, and periodic synchronization via the Hopf bifurcation theory. From the above analyses, an artificial ring neural network is constructed using 100 memristive neurons and resistive synapses to further study the coupled mechanism, generating exotic spatiotemporal patterns such as chimera death, amplitude chimera, solitary states, and asynchronization because of symmetry breaking. This sheds new light on exploring exotic spatiotemporal patterns of networks based on memristive neurons from the perspective of the nonlinear circuit theory.

High-Dimensional Physical Reservoir with Back-End-of-Line-Compatible Tin Monoxide Thin-Film Transistor.

This work demonstrates a physical reservoir using a back-end-of-line compatible thin-film transistor (TFT) with tin monoxide (SnO) as the channel material for neuromorphic computing. The electron trapping and time-dependent detrapping at the channel interface induce the SnO·TFT to exhibit fading memory and nonlinearity characteristics, the critical assets for physical reservoir computing. The three-terminal configuration of the TFT allows the generation of higher-dimensional reservoir states by simultaneously adjusting the bias conditions of the gate and drain terminals, surpassing the performances of typical two-terminal-based reservoirs such as memristors. The high-dimensional SnO TFT reservoir performs exceptionally in two benchmark tests, achieving a 94.1% accuracy in Modified National Institute of Standards and Technology handwritten number recognition and a normalized root-mean-square error of 0.089 in Mackey-Glass time-series prediction. Furthermore, it is suitable for vertical integration because its fabrication temperature is <250 °C, providing the benefit of achieving a high integration density.

Charge Trapping and Emission during Bias Temperature Stressing of Schottky Gate GaN-on-Silicon HEMT Structures Targeting RF/mm Wave Power Amplifiers.

For operation as power amplifiers in RF applications, high electron mobility transistor (HEMT) structures are subjected to a range of bias conditions, applied at both the gate and drain terminals, as the device is biased from the OFF- to ON-state conditions. The stability of the device threshold voltage (Vt) condition is imperative from a circuit-design perspective and is the focus of this study, where stresses in both the ON and OFF states are explored. We see rapid positive threshold voltage increases under negative bias stress and subsequent recovery (i.e., Vt reduces), whereas conversely, we see a negative Vt shift under positive stress and Vt increase during the subsequent relaxation phase. These effects are correlated with the thickness of the GaN layer and ultimately result from the deep carbon-acceptor levels in the C-GaN back barrier incorporated to screen the buffer between the silicon substrate and the epitaxially grown GaN layer. Methods to mitigate this effect are explored, and the consequences are discussed.

Design and sensitivity analysis of a vertical TFET with dielectric pocket for its use as label free biosensor

A comprehensive analysis of a dielectrically modulated vertical tunnel field effect transistor (VTFET) as a label free biosensor is presented in this article. The proposed structure considers an n+ pocket at the source /channel interface and a dielectric pocket at channel/drain interface. The sensitivity of the VTFET biosensor has been investigated, introducing neutral and charged biomolecules of different dielectric constants at the nanogap cavity. The n+ doped pocket introduced at the source/channel junction improves the output characteristics of the proposed VTFET due to its conduction mechanism in both lateral and vertical directions, thereby improving the sensitivity of VTFET biosensor as well. The proposed VTFET biosensor gains the sensitivity in the order of 105 for a fully filled cavity. Moreover, the HfO2 dielectric pocket at the channel/drain interface suppresses the deteriorating ambipolar behaviour and also enhances the ambipolar current sensitivity compared to a VTFET biosensor without dielectric pocket. Thus, it is perceived that the main drawback of TFET, ambipolar nature, has evolved as an advantage for sensing applications. The VTFET biosensor has been analyzed with regards to variations in dielectric constant of cavity, density of charge, length and height of cavity, mole fraction and also operating temperature at a particular bias condition to judge its sensing capability. A status map has been presented where the proposed VTFET biosensor has been compared with some of the significant works reported in literature in terms of sensitivity and selectivity.