Leakage Current Research Articles

Unveiling microstructural damage for leakage current degradation in SiC Schottky diode after heavy ions irradiation under 200 V

Single-event burnout and single-event leakage current (SELC) in silicon carbide (SiC) power devices induced by heavy ions severely limit their space application, and the underlying mechanism is still unclear. One fundamental problem is lack of high-resolution characterization of radiation damage in the irradiated SiC power devices, which is a crucial indicator of the related mechanism. In this Letter, high-resolution transmission electron microscopy (TEM) was used to characterize the radiation damage in the 1437.6 MeV 181Ta-irradiated SiC junction barrier Schottky diode under 200 V. The amorphous radiation damage with about 52 nm in diameter and 121 nm in length at the Schottky metal (Ti)–semiconductor (SiC) interface was observed. More importantly, in the damage site the atomic mixing of Ti, Si, and C was identified by electron energy loss spectroscopy and high-angle annular dark-field scanning TEM. It indicates that the melting of the Ti–SiC interface induced by localized Joule's heating is responsible for the amorphization and the possible formation of titanium silicide, titanium carbide, or ternary phases. The mushroom-like hillock in the Ti layer can be attributed to Rayleigh–Taylor instability, as another evidence for ever-happened localized melting near the Schottky interface. These modifications at nanoscale in turn cause localized degradation of the Schottky contact, resulting in permanent increase in leakage current. This experimental study provides very valuable clues for a thorough understanding of the SELC mechanism in SiC diodes.

Photoelectric property degradation of graded barrier InAs/GaSb type II superlattice long-wave infrared detectors under 1 MeV electron irradiation

Amid rapid advancements in aerospace science and technology, studying the effects of space radiation on an infrared detector is crucial for enhancing their reliability in radiation environments, particularly against electrons—one of the most damaging charged particles. Barrier structures significantly reduce dark current without any substantial degradation in the optical performance of the devices. Consequently, they are being investigated for use in extreme environments. This paper presents a study on the performance degradation of InAs/GaSb type II superlattice (T2SLs) long-wave infrared (LWIR) detectors with a graded barrier structure under 1 MeV electron irradiation and analyzes potential damage mechanisms. The findings indicate that 1 MeV electron irradiation causes both ionization and displacement damage to the graded barrier InAs/GaSb T2SL LWIR detectors. After irradiation with a fluence of 2 × 1015 e/cm2, the device’s dark current density has increased by approximately two orders of magnitude, while the quantum efficiency has decreased by approximately one order of magnitude. As the device mesa shrinks, the sensitivity of dark current to radiation exposure increases. Electron irradiation notably exacerbates surface leakage and bulk dark current, with a pronounced increase in surface leakage current. The study also reveals that electron irradiation primarily enhances the dark current by introducing defect states, thereby leading to device performance degradation.

Reduced trap state density in AlGaN/GaN HEMTs with low-temperature CVD-grown BN gate dielectric

In this Letter, low-temperature (400 °C) chemical vapor deposition-grown boron nitride (BN) was investigated as the gate dielectric for AlGaN/GaN metal–insulator–semiconductor high electron mobility transistors (MISHEMTs) on a Si substrate. Comprehensive characterizations using x-ray photoelectron spectroscopy, reflection electron energy loss spectroscopy, atomic force microscope, high-resolution transmission electron microscopy, and time-of-flight secondary ion mass spectrometry were conducted to analyze the deposited BN dielectric. Compared with conventional Schottky-gate HEMTs, the MISHEMTs exhibited significantly enhanced performance with 3 orders of magnitude lower reverse gate leakage current, a lower off-state current of 1 × 10−7 mA/mm, a higher on/off current ratio of 108, and lower on-resistance of 5.40 Ω mm. The frequency-dependent conductance measurement was performed to analyze the BN/HEMT interface, unveiling a low interface trap state density (Dit) on the order of 5 × 1011–6 × 1011 cm−2 eV−1. This work shows the effectiveness of low-temperature BN dielectrics and their potential for advancing GaN MISHEMTs toward high-performance power and RF electronics applications.

Thermal stability of TiN gate electrode for 4H-SiC MOSFETs and integrated circuits

Abstract In this research, the thermal stability of single stage amplifier based on 4H-SiC MOSFET with a TiN gate electrode was investigated. The results show that, after 100-hour aging at 400℃ in N2 ambient, the amplifier maintained good performance with stable voltage gain. The thermal stability of the amplifier results from the stability of Ni/Nb/4H-SiC source/drain ohmic contact, implanted load resistor, and MOS structure with the TiN gate electrode. The results obtained from the 4H-SiC MOS structure show that the interface trap density at the SiO2/SiC decreases during the aging process. While the gate leakage current of the capacitor based on Al gate electrode increases, it remains stable in structures with TiN gate electrodes after 100-hour aging. The results obtained in this study indicate that TiN is promising for the gate electrode of 4H-SiC MOSFETs for high-temperature applications.

A full-head model to investigate intra and extracochlear electric fields in cochlear implant stimulation

Objective. Despite the widespread use and technical improvement of cochlear implant (CI) devices over past decades, further research into the bioelectric bases of CI stimulation is still needed. Various stimulation modes implemented by different CI manufacturers coexist, but their true clinical benefit remains unclear, probably due to the high inter-subject variability reported, which makes the prediction of CI outcomes and the optimal fitting of stimulation parameters challenging. A highly detailed full-head model that includes a cochlea and an electrode array is developed in this study to emulate intracochlear voltages and extracochlear current pathways through the head in CI stimulation. Approach. Simulations based on the finite element method were conducted under monopolar, bipolar, tripolar (TP), and partial TP modes, as well as for apical, medial, and basal electrodes. Variables simulated included: intracochlear voltages, electric field (EF) decay, electric potentials at the scalp and extracochlear currents through the head. To better understand CI side effects such as facial nerve stimulation, caused by spurious current leakage out from the cochlea, special emphasis is given to the analysis of the EF over the facial nerve. Main results. The model reasonably predicts EF magnitudes and trends previously reported in CI users. New relevant extracochlear current pathways through the head and brain tissues have been identified. Simulated results also show differences in the magnitude and distribution of the EF through different segments of the facial nerve upon different stimulation modes and electrodes, dependent on nerve and bone tissue conductivities. Significance. Full-head models prove useful tools to model intra and extracochlear EFs in CI stimulation. Our findings could prove useful in the design of future experimental studies to contrast FNS mechanisms upon stimulation of different electrodes and CI modes. The full-head model developed is freely available for the CI community for further research and use.

Optimizing TCAD Model and Temperature-Dependent Analysis of Pt/AlN Schottky Barrier Diodes for High-Power and High-Temperature Applications

This research presents a comprehensive investigation and optimization of the Pt/AlN Schottky Barrier diode (SBD) using technology computer-aided design (TCAD) modeling. The study explores the electrical characteristics of AlN SBDs with various metal contacts, including Aluminum (Al), Silver (Ag), Tungsten (W), Gold (Au), Nickel (Ni), and Platinum (Pt). Through the comparative analyses of different metal/AlN Schottky contacts, the Pt/AlN structure emerges as the most promising due to its superior barrier height and lower leakage current. At [Formula: see text]K, the diode demonstrates a barrier height of 2.72[Formula: see text]V, a nearly ideal leakage current of 0.046[Formula: see text]pA, and a breakdown voltage of 363[Formula: see text]V. The research extends to examining the temperature-dependent electrical behavior of Pt/AlN Schottky diodes, particularly for high-power and high-temperature applications. Analysis carried out across temperatures ranging from [Formula: see text]K to [Formula: see text]K reveals a trend of increasing ON resistance and consistently lower leakage current with rising temperature. Importantly, the study indicates that the impact of temperature on the barrier height and breakdown voltage of the diode is negligible, thus rendering it suitable for high-temperature operation. Leveraging the unique properties of AlN as an ultra-wide bandgap material within the III-V compound semiconductor family, this research provides valuable insights into the potential applications of Pt/AlN Schottky contact. The study highlights that the Pt/AlN Schottky contact is effective not only for high-power, high-temperature SBDs but also as superior metal/semiconductor gate contacts for field-effect transistors (FETs). Their suitability is attributed to their ability to handle high voltages, minimize reverse leakage current, and demonstrate improved thermal stability.

A novel MTCMOS based 8T2M NVSRAM design for low power applications with high temperature endurance

This research investigates, for the first time, a novel eight-transistor-two-memristor (8T2M) nonvolatile static random access memory (NVSRAM) with 7-nm technology. The key innovation in this design lies in the incorporation of multiple-threshold complementary metal oxide semiconductor (MTCMOS) technology with power gating technique, which enables efficient power management and enhanced performance with low leakage current. The implementation of multiple threshold voltage levels allows for dynamic control of transistor behavior, optimizing power consumption and read/write speeds. As compared to a traditional six-transistor (6T) static random access memory (SRAM) cell, it has been ascertained that there is a 33% enhancement in the read margin and an 18% improvement in the write margin. Moreover, the delay for read, write ‘0’ and write ‘1’ is also minimized by 63.89%, 37.99% and 42.77%. Furthermore, the power attenuation is also reduced for read and write by 63.02% and 81.6%, respectively with respect to a conventional SRAM.

Effect of hydrogen poisoning on p-gate AlGaN/GaN HEMTs

In this work, we investigate the degradation behavior and mechanism of p-gate AlGaN/GaN high-electron mobility transistors (HEMTs) for the first time under hydrogen (H2) atmosphere. The experimental results reveal significant decrease in drain-to-source current, negative drift in threshold voltage, increase in off-state gate leakage current, and deterioration of subthreshold swing in the p-gate AlGaN/GaN HEMT after H2 treatment. The degradation of the electrical parameters is considered to hydrogen poisoning phenomenon. Through secondary ion mass spectrometry and variable temperature photoluminescence spectroscopy, we observe the increase in hydrogen concentration in the p-GaN layer and the formation of electrically inactive Mg–H complexes after H2 treatment. As results, the effective hole concentration decreases and the trap density of the device increases, which are confirmed by Hall effect measurement and low-frequency noise analysis, respectively. The detrimental effect of hydrogen on p-gate AlGaN/GaN HEMTs can be attributed primarily to the compensation of Mg doping and the generation of defects.

A Self-Sovereign Identity Privacy-Preserving Scheme for Logistics Transportation Based on One-Time-Use Tokens

The advancement of the logistics industry has fostered the enhancement of operational efficacy within the socioeconomic domain. However, the current inevitable privacy leaks in the process of logistics transportation have seriously affected the development of the industry, which led to a crisis of consumer trust and even caused economic recession. This paper proposes a self-sovereign identity privacy protection scheme tailored specifically for logistics transportation contexts. First, the scheme entails furnishing users with one-time-use tokens while establishing decentralized identities capable of concealing identity information and ensuring the secure transmission of data. Furthermore, the scheme integrates fuzzy identity-based encryption to encrypt identity information, thereby guaranteeing the confidentiality and integrity of logistics user identities along with their associated data. Compared with other schemes, this scheme exhibits superior security in the realm of logistics transportation. Its targeted encryption technology and self-sovereignty strategies address the critical issue of privacy leakage, thereby safeguarding consumer privacy rights and interests while facilitating the sustainable development of the logistics industry.

Effect of tensile and compressive strain on the gate leakage current and inverse piezoelectric effect in AlGaN/GaN HEMT devices

The influence of external strain on the gate leakage current of AlGaN/GaN high-electron-mobility transistors was studied. The magnitude of the leakage current increased by 39% under 0.1% tensile strain but decreased by 23% under −0.1% compressive strain. The leakage current obeyed the Poole–Frenkel conduction mechanism, demonstrating a decrease/increase in the barrier height for electron emission from the trap state into the continuum dislocation state. Furthermore, the magnitude of critical reverse stressing voltage for the onset of degradation induced by the inverse piezoelectric effect became lower/higher under tensile/compressive strain compared with that of the initial state, which was attributed to the modification of the total stress in the film. In addition, using the transient current method, it was established that the detrapping time constant for the traps in the AlGaN barrier increased as a result of the tensile strain, which is ascribed to movement of the dislocation level away from the conduction band.

A Multiscale Simulation on Aluminum Ion Implantation-Induced Defects in 4H-SiC MOSFETs

Aluminum (Al) ion implantation is one of the most important technologies in SiC device manufacturing processes due to its ability to produce the p-type doping effect, which is essential to building p–n junctions and blocking high voltages. However, besides the doping effect, defects are also probably induced by the implantation. Here, the impacts of Al ion implantation-induced defects on 4H-SiC MOSFET channel transport behaviors are studied using a multiscale simulation flow, including the molecular dynamics (MD) simulation, density functional theory (DFT) calculation, and tight-binding (TB) model-based quantum transport simulation. The simulation results show that an Al ion can not only replace a Si lattice site to realize the p-doping effect, but it can also replace the C lattice site to induce mid-gap trap levels or become an interstitial to induce the n-doping effect. Moreover, the implantation tends to bring additional point defects to the 4H-SiC body region near the Al ions, which will lead to more complicated coupling effects between them, such as degrading the p-type doping effect by trapping free hole carriers and inducing new trap states at the 4H-SiC bandgap. The quantum transport simulations indicate that these coupling effects will impede local electron transports, compensating for the doping effect and increasing the leakage current of the 4H-SiC MOSFET. In this study, the complicated coupling effects between the implanted Al ions and the implantation-induced point defects are revealed, which provides new references for experiments to increase the accepter activation rate and restrain the defect effect in SiC devices.

Efficacy and safety of focal pulsed-field ablation for ventricular arrhythmias: two-centre experience.

A pulsed electric field(PF) energy source is a novel potential option for catheter ablation of ventricular arrhythmias(VA) as it can create deeper lesions, particularly in scarred tissue. However, very limited data exist on its efficacy and safety. This prospective observational study reports the initial experience with VA ablation using focal PF. The study population consisted of 44patients (16 women, aged 61±14years) with either frequent ventricular premature complexes (VPC) (48%) or scar-related ventricular tachycardia (VT) (52%). Ablation was performed using an irrigated 4-mm tip catheter and a commercially available PF generator. On average, 16±15PF applications (25A) were delivered per patient. Acute success was achieved in 84% of patients as assessed by elimination of VPC or reaching non-inducibility of VT. In 3 cases (7%), a transient conduction system block was observed during PF applications remotely from the septum. Root analysis revealed that this event was caused by current leakage from the proximal shaft electrodes in contact with the basal interventricular septum. Acute elimination of VPC was achieved in 81% patients and non-inducibility of VT in 83% patients. At the three-month follow-up, persistent suppression of the VPC was confirmed on Holter monitoring in 81% patients. In the VT group, the mean follow-up was 116±75days and a total of 52% patients remained free of any VA. PF catheter ablation of a broad spectrum of VA is feasible with acute high efficacy, however, the short-term follow-up is less satisfactory for patients with scar-related VT.

A novel MTCMOS based 8T2M NVSRAM design for low power applications with high temperature endurance

Abstract This research investigates, for the first time, a novel eight-transistor-two-memristor (8T2M) nonvolatile 
static random access memory (NVSRAM) with 7-nm technology. The key innovation in this design lies 
in the incorporation of multiple-threshold complementary metal oxide semiconductor (MTCMOS) 
technology with power gating technique, which enables efficient power management and enhanced 
performance with low leakage current. The implementation of multiple threshold voltage levels allows 
for dynamic control of transistor behavior, optimizing power consumption and read/write speeds. As 
compared to a traditional six-transistor (6T) static random access memory (SRAM) cell, it has been 
ascertained that there is a 33% enhancement in the read margin and an 18% improvement in the write 
margin. Moreover, the delay for read, write ‘0’ and write ‘1’ is also minimized by 63.89%, 37.99% and 
42.77%. Furthermore, the power attenuation is also reduced for read and write by 63.02% and 81.6%, 
respectively with respect to a conventional SRAM.

Defects and oxygen impurities in ferroelectric wurtzite Al1−xScxN alloys

III-nitrides and related alloys are widely used for optoelectronics and as acoustic resonators. Ferroelectric wurtzite nitrides are of particular interest because of their potential for direct integration with Si and wide bandgap semiconductors and unique polarization switching characteristics; such interest has taken off since the first report of ferroelectric Al1−xScxN alloys. However, the coercive fields needed to switch polarization are on the order of MV/cm, which are 1–2 orders of magnitude larger than oxide perovskite ferroelectrics. Atomic-scale point defects are known to impact the dielectric properties, including breakdown fields and leakage currents, as well as ferroelectric switching. However, very little is known about the native defects and impurities in Al1−xScxN and their effect on the dielectric and ferroelectric properties. In this study, we use first-principles calculations to determine the formation energetics of native defects and unintentional oxygen incorporation and their effects on the polarization switching barriers in Al1−xScxN alloys. We find that nitrogen vacancies are the dominant native defects, and unintentional oxygen incorporation on the nitrogen site is present in high concentrations. They introduce multiple mid-gap states that can lead to premature dielectric breakdown and increased temperature-activated leakage currents in ferroelectrics. We also find that nitrogen vacancy and substitutional oxygen reduce the switching barrier in Al1−xScxN at low Sc compositions. The effect is minimal or even negative (increases barrier) at higher Sc compositions. Unintentional defects are generally considered to adversely affect ferroelectric properties, but our findings reveal that controlled introduction of point defects by tuning synthesis conditions can instead benefit polarization switching in ferroelectric Al1−xScxN at certain compositions.

PERFORMANCE OF ZINC OXIDE-VANADIUM PENTOXIDE VARISTORS IN MEDIUM VOLTAGE SURGE ARRESTERS

Metal oxide varistor (MOV) discs (Ø28 mm × 12 mm) made of 97.5 mol.% zinc oxide (ZnO), and 0.5 mol.% each of vanadium pentoxide (V2O5), tin (IV) oxide (SnO2), antimony(III) oxide (Sb2O3), cobalt(II, III) oxide (Co3O4), and chromium(III) oxide (Cr2O3) additives were produced using powder metallurgy. The obtained MOVs were polycrystalline with high density. This study focused on analyzing the microstructure and mechanical and electrical properties of the MOVs. The developed MOVs had a fine-grained microstructure with an average ZnO grain size of about 10 μm. The Ag-coated MOV discs tested in a range of 100 – 1300 V ac exhibited a leakage current of 0.033 – 1.420 mA and a minimum varistor voltage of 2.37 ± 0.15 kV. After conducting functional tests on Ag-coated MOVs installed in polymer-housed surge arresters, it was found that they are suitable for use in medium voltage arresters with a nominal voltage (Un) of 25 kV, a continuous operating voltage (Uc) of 12 kV and a leakage current (IL) of 1 mA.

Failure type and failure level detection of insulators according to monitored leakage current

Due to the ever-increasing growth of electric energy consumption, the production of high-quality, reliable and high-reliability electricity is very important. Therefore, it is essential to have distribution and sub-transmission networks with a good reliability factor. In power distribution and sub-transmission lines, it is necessary to somehow isolate the conductors under voltage from the towers, and insulators are used for this purpose. These insulators have two main tasks. One of the main tasks of insulators is to isolate (insulate) the line conductor from the body of the tower. The insulators must be able to isolate the high voltages of the lines from the body of the tower without having a leakage current, and on the other hand, the insulators must be able to withstand the mechanical forces resulting from the weight of the conductors and the applied forces caused by wind and ice. Also, leakage current is one of the important parameters for condition monitoring of insulators in power grid lines. Failure to inspect the insulation for contamination and health conditions will lead to insulator failure and will cause faults in the electrical system. Therefore, it is very important to monitor the condition of the insulator. Based on this, in this paper, according to the data related to leakage current and also according to the introduced wear out function, a procedure for measuring the condition of insulators has been obtained. Finally, the condition of each insulator will be determined according to the defined indicators. Also, the failure level of each monitored data will be obtained using sensitivity analysis.

Water-saving control system based on multiple intelligent algorithms

Water conservation has become a global problem as the population increases. In many densely populated cities in China, leaks from century-old pipe works have been widespread. However, entirely eradicating the issues involves replacing all water networks, which is costly and time-consuming. This paper proposed an AI-enabled water-saving control system with three control modes: time division control, flow regulation, and critical point control according to actual flow. Firstly, based on the current leaking situation of water supply networks in China and the capability level of China’s water management, a water-saving technology integrating PID control and a series of deep learning algorithms was proposed. Secondly, a multi-jet control valve was designed to control pressure and reduce water distribution network cavitation. This technology has been successfully applied in industrial settings in China and has achieved gratifying water-saving results.

Self-Balanced Switched-Capacitor Common-Grounding Boost Multilevel Inverter

Transformerless inverters have been extensively deployed in photovoltaic (PV) applications, owing to features such as high efficiency, high power quality, and low cost. However, the leakage current in such inverters due to the absence of galvanic isolation has resulted in several topological modifications. This paper introduces a single-input switched-capacitor (SC)-based multilevel inverter (MLI) that is capable of eliminating the leakage current due to its common-ground structure. Also, the proposed inverter has the capability of single-stage voltage boosting, which is essential in PV systems. The series–parallel switching facilitates the self-balancing of SCs, which, in turn, assists in voltage boosting. Moreover, the proposed MLI synthesizes a seven-level output using only eight switches. Following an in-depth analysis of the circuit operation, modulation scheme, and power losses, a detailed comparison among recently developed seven-level MLIs is carried out, which verifies the design's superiority. Extensive simulation and experimental results are presented to validate the prominent features of the seven-level MLI under dynamic operating conditions.

Thermally Oxidized Memristor and 1T1R Integration for Selector Function and Low-Power Memory.

Resistive switching memories have garnered significant attention due to their high-density integration and rapid in-memory computing beyond von Neumann's architecture. However, significant challenges are posed in practical applications with respect to their manufacturing process complexity, a leakage current of high resistance state (HRS), and the sneak-path current problem that limits their scalability. Here, a mild-temperature thermal oxidation technique for the fabrication of low-power and ultra-steep memristor based on Ag/TiOx/SnOx/SnSe2/Au architecture is developed. Benefiting from a self-assembled oxidation layer and the formation/rupture of oxygen vacancy conductive filaments, the device exhibits an exceptional threshold switching behavior with high switch ratio exceeding 106, low threshold voltage of ≈1V, long-term retention of >104s, an ultra-small subthreshold swing of 2.5mVdecade-1 and high air-stability surpassing 4 months. By decreasing temperature, the device undergoes a transition from unipolar volatile to bipolar nonvolatile characteristics, elucidating the role of oxygen vacancies migration on the resistive switching process. Further, the 1T1R structure is established between a memristor and a 2H-MoTe2 transistor by the van der Waals (vdW) stacking approach, achieving the functionality of selector and multi-value memory with lower power consumption. This work provides a mild-thermal oxidation technology for the low-cost production of high-performance memristors toward future in-memory computing applications.

Improvement in Performance and Stability of PbS QD/IGZO Phototransistors Through the Introduction of Ga2O3 Film for Broadband Sensor Applications.

The development of broadband photosensors has become crucial in various fields. Indium-gallium-zinc oxide (IGZO, In:Ga:Zn = 1:1:1) phototransistors with PbS quantum dots (QDs) have shown promising features for such sensors, such as reasonable mobility, low leakage current, good photosensitivity, and low-cost fabrication. However, the instability of PbS QD/IGZO phototransistors under an air atmosphere and prolonged storage remain serious concerns. In this article, two concepts to improve the reliability of PbS QD/IGZO phototransistors were implemented. P-type doping in the PbS QD layer through oxidation allows increasing the built-in potential between IGZO and PbS QDs, leading to enhancement in photoinduced electron-hole pair creation. Second, agglomeration and fusion of a PbS QDs layer were controlled via thermal annealing, which facilitated the transport of photocreated carriers. The p-type doping and interconnection of a PbS QD layer can be achieved by deposition and subsequent thermal annealing of gallium oxide (Ga2O3) on PbS QD/IGZO stacks. The resulting Ga2O3/PbS QD/IGZO phototransistors exhibited high-performance switching characteristics under dark conditions. Notably, they showed a remarkable photoresponsivity of 196.69 ± 4.05 A/W and a detectivity of (5.47 ± 1.4) × 1012 Jones even at a long-wavelength illumination of 1550 nm. While the unpassivated PbS/IGZO phototransistor suffered serious degradation in optical performance after 2 weeks of storage, the Ga2O3/PbS QD/IGZO phototransistor demonstrated enhanced stability, maintaining high performance for over 5 weeks. These findings suggest that Ga2O3/PbS QD/IGZO phototransistors offer a feasible approach for the fabrication of large-scale active matrix broadband photosensor arrays, potentially revolutionizing optical sensing in various cutting-edge applications.