Reverse Bias Research Articles

Self-cooling in reverse biased p-InAsSbP/n-InAs0.9Sb0.1 heterostructures

2D thermal radiation distribution together with I–V and L–I characteristics has been measured and analyzed in forward and reverse biased p–n heterostructures based on InAs0.9Sb0.1 and grown onto n-InAs substrates. The measurements revealed a sufficient difference in the temperature distribution onto the sample surface at forward and reverse bias, which is explained by an impact of heat pump operation initiated by an electron–phonon interaction at the p–n junction and diode contacts at U < 0.

Using Layer-by-layer Assembled Clay Composite Junctions to Enhance the Water Dissociation in Bipolar Membranes.

Bipolar membranes (BPMs) with a layer-by-layer (LbL) assembled montmorillonite (K30 MMT) clay-polyelectrolyte (PE) composite junction coated onto a sulfonated poly(ether ether ketone (SPEEK)) electrospun support are prepared, characterized and their water dissociation performance is analyzed. In particular, the focus is on the effect of the presence of the K30 MMT clay as a catalyst for water dissociation, the bilayer number (three, six, and nine), and the PE strength (poly(ethylenimine) (PEI) as a weak PE and poly(diallyl dimethylammonium chloride) (PDADMAC) as a strong PE) on the BPM performance. The BPMs are prepared by electrospinning and hot pressing SPEEK and the Fumion FAA-3 polymer. Adding the composite multilayers in the BPM junction decreases the membrane area resistance in reverse bias from 560 to 21 Ohms cm2 for the best-performing modified BPM. The bilayer number has limited influence on the overall membrane resistance, while the PDADMAC BPMs outperform the PEI BPMs due to the higher and more stable PE and clay adsorptions. Electrochemical impedance spectroscopy shows that the depletion layer thickness decreases exponentially with the number of bilayers as the water dissociation reaction becomes less dependent on the junction electric field. Furthermore, the higher Donnan exclusion at the modified junctions improves the BPM permselectivity 3-fold compared to the BPM containing no catalyst. Altogether, these improvements lead to 6.7 times less energy being used in BPM electrodialysis for the production of acid and base when a BPM with composite LBL junction is used compared to a BPM without catalyst. Thus, adding MMT clay composite LbL catalyst to BPM junctions is a promising method to improve the efficiency and reduce the energy consumption of electrochemical processes that rely on BPMs.

Suppressing the Dark Current Under Forward Bias for Dual‐Mode Organic Photodiodes

AbstractTremendous research efforts are developed to suppress the reverse dark current (Jd) and enhance the responsivity of organic photodiodes (OPDs). The functional layers of traditional OPDs usually follow the principle of energy level alignment to make unobstructed photo‐carriers transport under reverse bias, but this inevitably leads to a large forward Jd. Herein, a universal strategy is proposed to manipulate the carrier dynamics and effectively suppress the forward Jd of OPDs, that is, tuning the energy level and electron traps of the anode interface layers (AILs). The bandgap and electron traps of typical organometallic chelate AIL (PEIE‐Co) can be well controlled by adjusting the component ratio of PEIE and metal ions. The wide bandgap increases the carrier injection barrier under reverse and forward bias, endowing OPD with a much lower Jd; the electron traps induce hole tunneling injection by capturing photo‐generated electrons under forward bias, thereby enabling the photomultiplication effect. The obtained OPD exhibits photoconductive/photomultiplication working mode at reverse/forward bias and the specific detectivity approaches ≈1013/1012 Jones, showing promise for adaptively detecting faint and strong light. This study presents an intelligent strategy to achieve dual‐mode OPDs, paving the way for the multifunctional development of photodetectors.

Neurolinguistic Priming and Gender Stereotype Effects in the Ratings of Justice vs. Authority Moral Violations: Republicans and Democrats

ABSTRACT An experimental method for assessing gender biases was used to compare Republicans’ and Democrats’ ratings of moral violations in the domains of justice vs. respect for authority. Four experimental conditions of a text-based survey instrument manipulated the gender of the protagonist and the location of the first instance of gender information in single-sentence moral violation vignettes. Results were consistent with the theoretical time course of neurolinguistic gender priming and the hypothesized influence of implicit stereotypes on moral judgments. Republicans demonstrated a gender bias in ratings of authority violations by rating violations committed by girls and women as worse when compared to a pronoun only condition. Democrats demonstrated the opposite bias by rating authority violations committed by boys and men as worse when compared to violations committed by girls and women. No significant bias was found for any of the justice violation conditions for either Republicans or Democrats.

Zr-Doping Strategy of High-Quality Cu2O/β-Ga2O3 Heterojunction for Ultrahigh-Performance Solar-Blind Ultraviolet Photodetection.

β-Ga2O3, as an ultrawide band gap semiconductor, has emerged as the most promising candidate in solar-blind photodetectors. The practical application of β-Ga2O3, however, suffers from intrinsic defects and suboptimal crystal quality within the devices. In this work, high-quality β-Ga2O3 was successfully synthesized by employing the Zr-doping strategy, which has facilitated the development of ultrahigh-performance solar-blind photodetectors based on Cu2O/β-Ga2O3 heterostructures. Structural analyses indicate that the strong Zr-O covalent bond effectively stabilizes the material, thereby eliminating oxygen vacancy defects. The Cu2O/β-Ga2O3 heterostructure photodetector demonstrates an ultrahigh responsivity and detectivity coupled with an external quantum efficiency. Furthermore, the device exhibits a photocurrent-to-dark current ratio of 3 × 105, showcasing its superior capability in detecting low-intensity deep ultraviolet signals, markedly surpassing previous heterostructure ultraviolet photodetectors. These exceptional performances are attributed to the effective elimination of oxygen vacancy defects in β-Ga2O3 and the variation of band alignment at the interface, which facilitate rapid separation of photogenerated electron-hole pairs under reverse bias. This study not only provides an enhanced and easy route to mitigate oxygen vacancy defects in oxide materials but also propels further exploration into the next generation of flexible, high-performance, solar-blind ultraviolet photodetectors.

Bipolar Membranes With Controlled, Microscale 3D Junctions Enhance the Rates of Water Dissociation and Formation

AbstractA soft lithographic method is developed for making bipolar membranes (BPMs) with catalytic junctions formed from arrays of vertically oriented microscale cylinders. The membranes are cast from reusable polydimethylsiloxane (PDMS) molds made from silicon masters, which are fabricated on 2″ to 4″ wafer scales by nanosphere lithography. High‐aspect‐ratio junctions are made on a length scale similar to the thickness of optimized catalyst layers for water dissociation, creating a platform for probing the dual effects of catalysis and local electric field at the microscale BPM junction. Optimized polymer materials and nanoscale metal oxide catalysts are used in this study. 3D BPMs are tested under reverse and forward bias conditions, exhibiting superior performance relative to their 2D counterparts. Under forward bias in H2‐O2 fuel cells, 3D BPMs achieve a current density of 1500 mA cm−2, ≈7 times higher than 2D membranes made from the same materials.

III–V heterostructure tunnel field-effect transistor operation at different temperature regimes

Tunnel field-effect transistors (TFETs) are a potential alternative to MOSFETs for low-temperature electronics. We provide an in-depth experimental characterization of TFETs analyzing the fundamental physical behavior at different temperature regimes. TFET characteristics from 13 to 300 K both in forward and reverse bias are discussed by employing a variation in InAs/InGaAsSb/GaSb heterojunction vertical nanowire devices. Evaluation of the TFET Negative Differential Resistance (NDR) characteristics at different temperatures is established as a technique to probe the dopant incorporation. It is observed that the temperature dependence of the Fermi degeneracy and Fermi-Dirac distribution largely influences the transistor performance at each operating temperature. Our investigation reveals that the TFETs demonstrate lower subthreshold swing than the physical limit of MOSFETs above 125 K. For low-temperature applications, the devices can be operated down to a low operating bias of 0.1 V, while for high temperature, a larger bias of 0.3 V is preferred.

Features of current flow in the n-CoFe2O4/n-CdTe heterojunction

n-CoFe2O4/n-CdTe heterojunctions with a current rectification ratio of 3·105 at voltages |V| = 1.5 V were made by spray pyrolysis of aqueous solutions of cobalt and iron salts on n-CdTe substrates. Based on the analysis of the temperature dependence of I-V-characteristics in the forward voltage range, a change in the mechanisms of current flow in n-CoFe2O4/n-CdTe heterojunctions was established from overbarrier at voltages of 3kT/q < V < 0.3 V to tunneling at voltages of 0.4 V < V < 1 V. The role of surface states in the formation of the energy profile of the heterojunction and the participation of energy levels in the band gap of n-CdTe in the formation of the tunnel current have been clarified. The reasons for the occurrence of negative differential resistance at the forward biases of the structure have been clarified. The current at reverse biases in the range −3 V < V < -3kT/q was analyzed. According to the analysis of the C-V-characteristics, an inversion layer was found in the heterojunction and its behavior from voltage was explained.

Chemical and structural features of spin-coated magnesium oxide (MgO) and its impact on the barrier parameters and current conduction process of Au/undoped-InP Schottky contact as an interfacial layer

This work examines the structural and chemical characteristics of spin-coated magnesium oxide (MgO) on undoped InP (un-InP) and its effects on the barrier parameters and current transport phenomena in the Au/un-InP Schottky contact (SC). Using XRD and XPS, the structural and chemical features of MgO are assessed, confirming that the MgO was deposited on un-InP. The current-voltage (log(I)-V) features were measured for the SC and Au/MgO/un-InP metal/insulator/semiconductor (MIS)-type Schottky contact. The MIS contact revealed an excellent rectification behavior as compared to the SC. The calculated barrier height (Φb) was higher for the MIS contact (0.61 eV) than the SC (0.52 eV), which implies that the MgO interlayer influences the Φb of the SC. The Φb was also estimated using the Cheung’s, Mikhelashvili and Norde procedures, the values are similar, indicating their stability and reliability. The acquired interface state density (NSS) of the MIS contact was less than the SC, proving that the MgO interlayer reduced the NSS. The ohmic behavior was observed in the lower bias region for the SC and MIS contacts, while the trap-free space-charge-limited current (SCLC) was noted in the moderate and upper bias regions of the MIS contact under forward bias. Poole-Frenkel emission (PFE) governs at a lower bias, while Schottky emission (SE) dominates at the upper bias of SC and MIS contacts under reverse bias. These findings demonstrate the potential application of MgO interlayer in advancing electronic devices.

Investigation of the leakage mechanism in solar-blind AlGaN p-i-n photodetector at high reverse bias

The leakage mechanism of solar-blind AlGaN p-i-n photodetectors has been investigated. By studying the temperature-dependent I–V curves, we determined that Poole–Frenkel emission is the main source of the leakage current, and the corresponding trap energy level is 0.61 eV. Cathodoluminescence measurement demonstrates that the leakage current of the device may be related to the deep-level traps in the p-AlGaN layer. An analysis of deep-level transient spectroscopy testing results for p-AlGaN suggests that nitrogen vacancies formed during the epitaxial growth of high Al-content p-AlGaN act as electron traps. The trap potential energy decreases at high reverse bias voltage, making trapped electrons easier to escape, which increases the leakage current.

Organic Bulk-Heterojunction Blends with Vertical Phase Separation for Enhanced Organic Photodetector Performance.

The ternary blending strategy is a fundamental approach that is widely recognized in the field of organic optoelectronics. In our investigation, leveraging the inherent advantages of the ternary component blending methodology, we introduced an innovative design for organic photodetectors (OPDs) aimed at reducing the dark current density (Jd) under reverse bias. This pioneering effort involved combining two distinct conjugated molecules (IT-4F and IEICO-4F) with a conjugated polymer (PM7), resulting in a composite material characterized by a well-defined vertical phase separation. To thoroughly explore device performance variations, we utilized a comprehensive array of analytical techniques, including atomic force microscopy (AFM) cross-section methodologies and Kelvin probe force microscopy (KPFM). Through the optimization of the blend ratio (PM7:IT-4F: IEICO-4F at 1:0.8:0.2), we achieved significant advancements. The resulting OPD demonstrated an exceptional reduction in JD, reaching a remarkably low value of 4.95 × 10-10 A cm-2, coupled with an ultra-high detectivity of 4.95 × 1013 Jones and an outstanding linear dynamic range exceeding 100 dB at 780 nm under a bias of -1V. Furthermore, the attained cutoff frequency reached an impressive 220 kHz, highlighting substantial improvements in device performance metrics. Of particular significance is the successful translation of this technological breakthrough into real-world applications, such as in heart rate sensing, underscoring its tangible utility and expanding its potential across various fields. This demonstrates its practical relevance and underscores its versatility in diverse settings.

How Does Politics Affect Quality of Public Transport Infrastructure?

While prior studies have investigated the impacts of political factors such as the ideological stance on quality of public infrastructure, there is a paucity of research on the political effects of re-election success, party fragmentation (political power), and the formation of new electoral consistency on quality of public transport infrastructure, which is represented in this paper by road maintenance efficiency. We employ an instrumental variable approach to mitigate a potential reverse causality bias inherent in literature. Our empirical results show that local governments whose political representatives were re-elected give rise to lower road maintenance efficiency. Local governments with new electoral constituencies report a higher road maintenance efficiency.

High-performance deep-ultraviolet photodetector based on a single-crystalline ϵ-Ga2O3/Sn-doped In2O3 heterojunction

Abstract Metastable ϵ-Ga2O3, with its superior physical properties and high substrate compatibility, demonstrates considerable potential in developing heterojunction deep-ultraviolet photodetectors (DUV PDs). Herein, we fabricate a high-performance DUV PD utilizing a single crystalline ϵ-Ga2O3/ Sn-doped In2O3 (ITO) heterojunction. Under a reverse bias of 15 V, the device exhibits a high responsivity of 506 A/W, an excellent UV/visible rejection ratio of 6.74 × 104, and a fast fall time of 40 ms while maintaining good performance across a broad illumination range of 90–4100 μW cm−2. Moreover, the device can operate in a self-powered mode at zero bias, further verifying the presence of a depletion region within the ϵ-Ga2O3/ITO heterojunction. Our results demonstrate that ϵ-Ga2O3 is promising for high-quality integration on ITO and application in DUV detection, offering new strategic directions for developing high-performance Ga2O3-based DUV PDs.

Association between dried fruit intake and kidney function: research from univariate and multivariate Mendelian randomized studies.

Observational studies have identified an association between dried fruit intake and kidney function. However, these studies have limitations such as vulnerability to confounders and reverse causality bias. Therefore, this study aimed to explore the potential causal relationship between dried fruit intake and kidney function. A two-sample Mendelian randomization (MR) study was conducted using a large-scale genome-wide association study dataset to investigate the causal relationship between dried fruit intake and kidney function markers (blood urea nitrogen (BUN), creatinine (CR), uric acid (UA), cystatin C (CyC), hematuria, microalbuminuria). The main analytical method was inverse variance weighting. In addition, we applied the MR Egger and weighted median to assess the robustness of the results. Finally, Multivariate Mendelian randomization (MVMR) was used to estimate the direct effect of dried fruit intake on kidney function markers. The univariate MR analysis showed that increased dried fruit intake was associated with lower kidney function markers, including BUN (β: -0.171, 95% confidence interval (CI): -0.239 to -0.102, p = 1.063 × 10-6), CR (β: -0.205, 95% CI: -0.311 to -0.099, p = 1.455 × 10-4), UA (β = -0.317, 95% CI: -0.384 to -0.249, p = 4.439 × 10-20), and CysC (β = -0.323, 95% CI: -0.384 to -0.249, p = 1.074 × 10-11); however, it was unrelated to hematuria and microalbuminuria. Causality persisted after performing MVMR analysis; however, with the addition of alcohol consumption and smoking as exposure factors, the causality for UA (β = -0.296, 95% CI: -0.523 to -0.068, p = 1.094 × 10-2) and CysC (β = -0.238, 95% CI: -0.465 to -0.011, p = 4.024× 10-2) weakened, while the causality for BUN (β = -0.038, 95% CI: -0.215 to 0.138, p = 6.698 × 10-1) and CR (β = -0.038, 95% CI: -0.431 to 0.046, p = 1.347 × 10-1) disappeared. Increased dried fruit intake was associated with lower kidney function markers (BUN, CR, UA, and CysC) in the absence of smoking and alcohol consumption; however, the causal relationship between dried fruit intake and BUN and CR disappeared in the presence of smoking and alcohol consumption. These results provide a promising avenue for delaying the course of chronic kidney disease.

A highly efficient adaptive body bias CMOS rectifier with double-side feedback at a tone of 2.4 GHz

ABSTRACT In this paper, a highly efficient adaptive body bias CMOS rectifier employed with double side feedback, operating with 2.4 GHz frequency, is proposed for radio frequency energy harvesting. The proposed circuit is built with 45 nm TSMC CMOS technology. In the suggested architecture, the double side feedback along with body bias is used to regulate threshold voltage. The use of PMOS transistors as a diode in reverse bias configuration has restricted the reverse current without compromising the forward current. This design has gained a maximum PCE of 82.25% and 77.29% at an input power of −23.90dBm and −23.74dBm and 500K and 100K load, respectively. The circuit has maintained a wide dynamic range of 30dbm at PCE >30% and registered an input sensitivity of −10.07dBm for attaining a DC output voltage of 1 V as compared to the previous works.

Evidence of Spin Reorientation from Γ4 to Γ2 and Sign Reversal Exchange Bias in CeCrO3 Nanoparticles

Herein, the temperature‐dependent magnetic structure and sign reversal exchange bias in CeCrO3 using magnetization data and time‐of‐flight neutron diffraction data which is given less attention among RCrO3 are investigated. While nuclear structural analysis using Rietveld refinement exhibits distorted orthorhombic structure within Pnma space group, temperature dependence of the magnetic structure using neutron diffraction reveals possible spin configurations, namely, Γ4, Γ2, and Γ1, within the temperature range of 6–300 K. Temperature‐dependent magnetization shows compensation temperature, Tcomp, at 58 K, spin reorientation temperature, TSR, at 15 K along with a Neel temperature, TN, at 260 K which is the outcome of the competition between canted antiferromagnetic ordering of Cr3+ ions and Ce3+ ions in CeCrO3. Furthermore, the magnetization versus magnetic field (M vs H) measurements indicate transition of the Γ4 spin structure to Γ2 spin structure around TSR which is further supported by reversible‐to‐irreversible changes observed in temperature‐dependent MFCC and MFCW. Moreover, a temperature‐driven sign reversal of exchange bias in CeCrO3 is observed, resulting from the competition between antiferromagnetic coupling between chromium moment (MCr) and cerium moment (MCe) in these nanoparticles. This intriguing behavior holds significant potential for the development of thermally assisted magnetic random access memory.

High‐Gain and Tunable Linear Photodetection in 2D Tunneling Heterostructures Through Potential Engineering

Abstract2D materials are extensively employed in the fabrication of high‐performance photodetectors owing to their exceptional physical properties. However, most 2D material photodetectors fail to sustain high gain under intense illumination due to the limited intrinsic trap states. Here, an n‐n type Bi2O2Se/SnSe2 van der Waals tunneling heterojunction photodetector with a detection range from visible to near‐infrared (VIS‐NIR) is presented. Under reverse bias, the heterojunction induces a significant electron barrier and hole potential well, ensuring low leakage current and ample hole defect states. Therefore, the photodetector demonstrated a responsivity of 1636.3 AW−1 and a detectivity of 1.39 × 1014 Jones under 660 nm illumination, maintaining a tunable linear dynamic range (LDR) of ≈74.7 dB. This performance is attributed to the hole potential well‐suppressing the recombination of photogenerated carriers, thereby enhancing the device's gain. Furthermore, the tunneling of photogenerated electrons within the heterojunction's space charge region under bias enables rapid response (75.1 and 15.6 µs). In summary, the study introduces a novel strategy to overcome the limited detection capabilities of 2D devices under intense illumination, characterized by outstanding linearity for rapid detection and high‐resolution imaging.

Design and experimental verification of a novel high-reliability variation of lateral doping (VLD) termination

Abstract A novel two-dimensional mesh-like variation of lateral doping (VLD) termination (M-VLD) is proposed, which modifies the conventional ring-shaped track VLD termination (R-VLD) mask into an interconnected mesh-like structure. The comparative simulations and experiments show that M-VLD can achieve better blocking capability and reliability than R-VLD. Vertical double diffusion MOSFET (VDMOS) with M-VLD achieves a maximum breakdown voltage ( B V max ) of 1588 V, which is 62 V higher than that of VDMOS with R-VLD. Furthermore, the devices with M-VLD exhibit lower leakage currents in 150 °C reverse-biased I − V test and successfully pass 1000 h-125 °C-1200 V high-temperature reverse bias (HTRB) test, while the devices with R-VLD fail to pass both tests.

Performance improvement of microLED‐to‐microLED visible light communication using reverse bias

AbstractLED‐to‐LED visible light communication (VLC), which uses LEDs not only for the transmitter but also for the receiver, is being studied as an efficient optical wireless communication technology that uses LED lighting infrastructure. In this paper, we investigate microLED‐to‐LED VLC, which uses microLEDs as both the transmitter and receiver. In particular, we conducted a study to improve the performance of microLED‐to‐microLED VLC. For this, we measured the performance depending on the transmitter and receiver LED color combination. In addition, the effects of zero bias and reverse bias at the receiver LED were investigated. We also investigated the improvement in the reverse bias when applying a transimpedance amplifier to the receiver LED. Finally, we experimentally demonstrated a data rate of 360 kbps in the microLED‐to‐microLED VLC.

Demonstration of high-frequency self-pulsing oscillations in an active silicon micro-ring cavity

We experimentally investigated the self-pulsing (SP) oscillations induced by the thermo-optic, free carrier, and Kerr nonlinear effects in integrated active silicon microring resonators. We demonstrate high frequency self-pulsing oscillations (up to 30 MHz) by applying a few millivolts of reverse bias voltage to the PIN junction of the active cavity. We illustrate that the shape of those oscillations (i.e., frequency and duty cycle) can be controlled by adjusting the CW input power and applying a reverse bias voltage to the PIN junction for carrier removal. This controlling is important for synchronizing the cavity which is crucial for neural network applications. Furthermore, we utilize a mathematical model for visualizing the stability regions by numerically studying coupled mode theory in silicon microcavity under different conditions.