Search Results (932)

Molybdenum oxide (MoO_X) has been widely utilized as a hole transport layer (HTL) in crystalline silicon (c-Si) solar cells, owing to characteristics such as a wide bandgap and high work function. However, the relatively low conductivity of MoO_X films and their poor contact performance at the MoO_X-based hole-selective contact severely degrade device performance, particularly because they limit the fill factor (FF). Oxygen vacancies are of paramount importance in governing the conductivity of MoO_X films. In this work, MoO_X films were modified through ultraviolet irradiation (UV-MoO_X), resulting in MoO_X films with tunable oxygen vacancies. Compared to untreated MoO_X films, UV-MoO_X films contain a higher density of oxygen vacancies, leading to an enhancement in conductivity (2.124 × 10⁻³ S/m). In addition, the UV-MoO_X rear contact exhibits excellent contact performance, with a contact resistance of 20.61 mΩ·cm², which is significantly lower than that of the untreated device. Consequently, the application of UV-MoO_X enables outstanding hole selectivity. The power conversion efficiency (PCE) of the solar cell with an n-Si/i-a-Si:H/UV-MoO_X/Ag rear contact reaches 24.15%, with an excellent FF of 84.82%. Full article

This review examines recent advances in Gallium Nitride (GaN) power semiconductor devices and their growing impact on the development of high-efficiency power conversion systems. It explores innovations in device design, packaging methods, and gate-driving strategies that have improved both performance and reliability. Key metrics such as switching speed, conduction losses, thermal management, and device robustness are analyzed, supported by reliability assessment techniques including Double-Pulse Testing (DPT). The discussion extends to current market dynamics and strategic industry initiatives that have catalyzed widespread GaN adoption. These combined insights highlight GaN’s role as a transformative material offering compact, efficient, and durable power solutions while identifying challenges that remain for broader implementation across diverse industries. Full article

Aluminum nitride (AlN), diamond, and β-phase gallium oxide (β-Ga₂O₃) belong to the family of ultra-wide bandgap (UWBG) semiconductors and exhibit remarkable properties for future power and optoelectronic applications. Compared to conventional wide bandgap (WBG) materials such as silicon carbide (SiC) and gallium nitride (GaN), they demonstrate clear advantages in terms of high-voltage, high-temperature, and high-frequency operation, as well as extremely high breakdown fields. In this work, numerical simulations are performed to evaluate and compare the radiative responses of AlN, diamond, and β-Ga₂O₃ when exposed to neutron irradiation covering the full atmospheric spectrum at sea level, from 1 meV to 10 GeV. The Geant4 simulation framework is used to model neutron interactions with the three materials, focusing on single-particle events that may be triggered. A detailed comparison is conducted, particularly concerning the generation of secondary charged particles and their distributions in energy, linear energy transfer (LET), and range given by SRIM. The contribution of the ¹⁴N(n,p)¹⁴C reaction in AlN is also specifically investigated. In addition, the study examines the consequences of these interactions in terms of electron-hole pair generation and charge deposition, and discusses the implications for the radiation sensitivity of these materials when exposed to atmospheric neutrons. Full article

Traditional zero-compensation techniques employed to improve sub-sampling phase-locked loop (SSPLL) stability often exacerbate spur degradation or incur excessive area overhead, rendering them unsuitable for high-resolution image sensor applications. This paper proposes a novel SSPLL based on capacitor multiplication technology. This capacitor multiplication technology employs dual charge pumps (CP1 and CP2) in a coordinated operational scheme where their charge/discharge states are inversely synchronized. The effective capacitance of the loop filter is thereby amplified without expanding the physical layout area dedicated to capacitive components. Meanwhile, the continued use of zero-compensation technology ensures the stability of the SSPLL. The proposed SSPLL is designed and verified in a 55 nm CMOS process. At a 1.2 GHz output frequency, simulation results show a spot phase noise of −131.5 dBc/Hz at 1 MHz offset, accompanied by an integrated RMS jitter of 549 fs across the 10 kHz to 40 MHz spectrum, spurs suppressed to −51.3 dB, while maintaining a power efficiency of 3.81 mW and a compact layout area of 0.064 mm². All the above results show that by introducing the novel dual-CP charge multiplication technology, the SSPLL can achieve low jitter and low power consumption performance while reducing the layout area, providing a new technical approach for its application in high-resolution image sensors. Full article

Photo(electro)-catalysis has increasingly attracted attention from researchers due to its wide applications in green chemical transformation, including organic synthesis and environmental remediation. As a promising candidate, the n-type semiconductor WO₃ possesses a suitable bandgap (~2.6 eV), good visible-light response, high chemical stability, and multi-electron transfer capability, thus endowing it with enormous potential in heterogeneous photocatalysis (PC) and photoelectrocatalysis (PEC) to address environment and energy issues. In this review, the recent research progress of WO₃-based photo(electro)-catalysts is examined and systematically summarized with regard to construction strategies and various application scenarios. To start with, the research background, functionalization methods and possible reaction mechanisms for WO₃ are introduced in depth. Key influencing factors, including light absorption capacity, charge carrier separation, and reusability, are also analyzed. Then, diverse applications of WO₃ for the elimination of organic pollutants (e.g., persistent organic pollutants and polymeric wastes) and green organic synthesis (i.e., oxidation, reduction, and other reactions) are intentionally discussed to underscore their vast potential in photo(electro)-catalytic performance. Finally, future challenges and insightful perspectives are proposed to explore effective WO₃-based materials. This comprehensive review aims to offer profound insights into innovative exploration of high-performance WO₃ semiconductor catalysts and guide new researchers in this field to better understand their vital roles in green organic synthesis and hazardous pollutants removal. Full article

Aluminum nitride (AlN) is a wide-bandgap semiconductor (6.2 eV) with a broad transparency window spanning from the ultraviolet (UV) to the mid-infrared (MIR) wavelength region, making it a promising material for integrated photonics. In this work, AlN thin films using reactive RF sputtering are deposited, followed by annealing at 600 °C in a nitrogen atmosphere to reduce slab waveguide propagation losses. After annealing, the measured loss is 0.84 dB/cm at 978 nm, determined using the prism coupling method. A complete microfabrication process flow is then developed for the realization of optical channel waveguides. A key challenge in the processing of AlN is its susceptibility to oxidation when exposed to water or oxygen plasma, which significantly impacts device performance. The process is validated through the fabrication of microring resonators (MRRs), used to characterize the propagation losses of the AlN channel waveguides. The fabricated MRRs exhibit a quality factor of 12,000, corresponding to a propagation loss of 4.4 dB/cm at 1510–1515 nm. The dominant loss mechanisms are identified, and strategies for further process optimization are proposed. Full article

The electrification of mobility sectors, including automotive, aerospace, and robotics, has accelerated the need for compact and high-efficiency power converters in electric motor drives. Wide-bandgap (WBG) semiconductor–based inverters offer significant advantages over conventional silicon IGBT inverters by enabling higher switching speeds, elevated switching frequencies, and improved power conversion efficiency. However, the adoption of high-frequency switching introduces several challenges, particularly increased motor neutral point voltage stress, originating from inverter common-mode (CM) voltage. The increased neutral point voltage directly elevates motor bearing voltage, the primary driver of motor bearing currents, among which electrostatic discharge machining (EDM) bearing current is the primary cause of bearing degradation in low-power motors. This paper experimentally investigates the root causes of the EDM phenomenon and identifies the key factors influencing its occurrence and severity in WBG-based drive systems. The conventional CM choke designs effectively attenuate motor CM currents and EMI; however, they are ineffective in suppressing EDM bearing currents. In this paper, an alternative CM choke design methodology is proposed to eliminate EDM bearing currents by optimizing the choke inductance to shift the motor CM antiresonance frequency below the inverter switching frequency, thereby ensuring that nearly all source CM voltage is absorbed by the choke. This design approach effectively minimizes the voltage appearing at the motor neutral point and across the bearings, thereby suppressing EDM bearing current spikes without affecting motor DM performance. The choke parameters are mathematically derived for optimal performance and validated through experimental testing on a 2.2 kW three-phase star-connected induction motor powered by a wide-bandgap two-level voltage-source inverter. Full article

In micro gas turbines, electrical power from the high-speed generator is delivered to the grid through a converter that influences overall efficiency and energy quality. This subsystem is often overlooked in efforts to improve turbine performance, which have traditionally focused on combustors and turbomachinery. This study investigates how replacing conventional silicon switching devices in the converter with silicon carbide technology can directly reduce greenhouse gas emissions from micro gas turbines. Although silicon carbide is widely used in electric vehicles and distributed energy systems, its emission reduction impact has not been assessed in micro gas turbines. A MATLAB-based model of a 100 kW Ansaldo Energia micro gas turbine was used to compare the performance of silicon and silicon carbide converters across the 20–100 kW operating range. Silicon carbide reduced total converter losses from 4.316 kW to 3.426 kW at full load, a decrease of 0.889 kW. This improvement lowered carbon dioxide emissions by 5.7 g/kWh and increased net electrical efficiency from 30.03% to 30.29%. Each turbine can therefore avoid about 1.53 tonnes of carbon dioxide annually, or 11.61 tonnes over a 50,000 h service life, without altering turbine design, combustor geometry, or fuel composition. This work establishes the first quantitative link between wide-bandgap semiconductor performance and direct greenhouse gas mitigation in micro gas turbines, demonstrating that upgrading converter technology from silicon to silicon carbide offers a deployable pathway to reduce emissions from micro gas turbines and, by extension, lower the carbon intensity of distributed generation systems. Full article

Metal–organic frameworks (MOFs) are novel porous crystalline materials formed through the self-assembly of metal ions and organic ligands. They have various advantages, including tunable chemical and electronic structures, high porosity, and large specific surface areas. Owing to their unique structural and physicochemical properties, MOFs have been widely applied in the fields of catalysis, supercapacitors, sensors, and drug recognition/delivery. However, the intrinsic poor stability and low electrical conductivity of conventional MOFs severely hinder their practical implementation. Graphdiyne (GDY), a unique carbon allotrope, features a new structure composed of both sp²- and sp-hybridized carbon atoms. Its distinct chemical and electronic configuration endow it with exceptional properties such as natural bandgap, uniform in-plane cavities, and excellent electronic conductivity. Integrating MOFs with GDY can effectively overcome the intrinsic limitations of MOFs and expand their potential applications. As emerging hybrid materials, MOF/GDY composites and their derivatives have attracted increasing attention in recent years. This article reviews recent advances in the synthesis strategies of MOF/GDY composites and their derivatives, along with their performance and applications in catalysis, energy storage, and biological sensors. It also discusses the future opportunities and challenges faced in the development of these promising composite materials, aiming to inspire interest and provide scientific guidance. Full article

Ultra-bandgap semiconductor material, β-gallium oxide (β-Ga₂O₃), has great potential for fabricating the next generation of high-temperature, high-voltage power devices due to its superior material properties and cost competitiveness. In addition, β-Ga₂O₃ has the advantages of high-quality, large-size, low-cost, and controllable doping, which can be realized by the melt method. It has a wide bandgap of 4.7–4.9 eV, a large breakdown field strength of 8 MV/cm, and a Baliga figure of merit (BFOM) as high as 3000, which is approximately 10 and 4 times that of SiC and GaN, respectively. These properties enable β-Ga₂O₃ to be strongly competitive in power diodes and metal-oxide-semiconductor field-effect transistor (MOSFET) applications. Most of the current research is focused on electrical characteristics of those devices, including breakdown voltage (V_BR), specific on-resistance (R_ON,SP), power figure of merit (PFOM), etc. Considering the rapid development of β-Ga₂O₃ diode technology, this review mainly introduces the research progress of different structures of β-Ga₂O₃ power diodes, including vertical and lateral structures with various advanced techniques. A detailed analysis of Ga₂O₃-based high-voltage power diodes is presented. This review will help our theoretical understanding of β-Ga₂O₃ power diodes as well as the development trends of β-Ga₂O₃ power application schemes. Full article

Silicon carbide (SiC) is a key material for electronics operating in harsh environments due to its wide bandgap, high thermal conductivity, and radiation hardness. In this work, we present a SPICE model for a 4H-SiC BJT and TTL inverter exposed to gamma radiation. The devices were fabricated using a dedicated SiC bipolar process at KTH (Sweden) and tested at the ⁶⁰Co Calliope (Italy) facility up to 800 krad _(Si). Experimental data, including Gummel plots and inverter transfer characteristics, were used to calibrate and refine a VBIC-based SPICE model. The adjusted model accounts for both bulk and surface degradation mechanisms by extracting parameters of forward current gain (βF), saturation current (IS), base resistance (RB), and forward transit time (TF). Results show a uniform degradation of BJTs, primarily manifested as reduced current gain and increased base resistance, while the inverter maintained functional operation up to 600 krad_(Si). Extrapolation of the SPICE model predicts a failure threshold near 16 Mrad_(Si), far exceeding the tolerance of conventional silicon circuits. By linking radiation-induced defects at the material and interface levels to circuit-level behavior, the proposed model enables realistic design and lifetime prediction of SiC integrated circuits for satellites, planetary missions, and other radiation-intensive applications. Full article

This work studies the impact of different physical and material parameters on the channel resistance, $R_{ch}$, and threshold voltage, $V_{th}$, of nanowire field-effect transistors (NWFETs). In particular, by means of detailed numerical simulations, we investigate the role of the channel length, nanowire diameter, gate oxide thickness, channel-doping concentration, energy bandgap, oxide thickness, and gate oxide permittivity in a wide range of temperatures (200–500 K). Our findings show that optimal values for both $R_{ch}$ and $V_{th}$ are achieved by reducing the nanowire channel length, as well as by increasing the nanowire diameter and doping concentration. Furthermore, NWFETs benefit from using wide-bandgap materials and thinner oxide layers with a higher permittivity. Notably, in short-channel NWFETs operating under ballistic transport, channel resistance remains nearly constant with temperature, governed by quantum conductance and injection statistics rather than temperature-sensitive scattering. These results underscore the complex interplay between material selection, doping levels, and device geometry in shaping the threshold voltage and the channel resistance of NWFETs. Also, they are useful for enhancing the device stability and advancing the design of NWFETs for the next-generation of nanoscale transistors. Full article

Cesium halide perovskite nanocrystals (PNCs) have emerged as promising materials for application in high-color-purity displays due to their exceptional optoelectronic properties, which include narrow emission linewidths, tunable bandgaps, and high photoluminescence quantum yields (PLQYs). However, preserving these characteristics during purification remains a major challenge as surface ligand detachment during the washing process can lead to increased defect states, reduced quantum efficiency, and spectral broadening. The choice of anti-solvent plays a crucial role in maintaining the structural and optical integrity of PNCs, as it directly influences ligand retention and material stability. In this study, we propose an optimized purification strategy for mixed-halide perovskite nanocrystals that incorporates post-synthetic ligand supplementation, in which controlled amounts of oleic acid (OA) and oleylamine (OAm) are sequentially introduced into the crude solution prior to anti-solvent treatment. This approach reinforces surface passivation, suppresses trap state formation, and minimizes halide loss. Consequently, a near-unity PLQY with narrow full-width-at-half-maximum emissions is achieved for both green- and red-emissive nanocrystals, markedly enhancing color purity and providing a promising route toward next-generation wide-color-gamut display technologies. Full article

To meet the requirements of integrated accelerometers for a high-precision reference voltage under wide supply voltage range, high current drive capability, and low power consumption, this paper presents a bandgap reference operational amplifier (op-amp) circuit implemented in CMOS/BiCMOS technology. The proposed design employs a folded-cascode input stage, a push–pull Class-AB output stage, an adaptive output switching mechanism, and a composite frequency compensation scheme. In addition, overcurrent protection and low-frequency noise suppression techniques are incorporated to balance low static power consumption with high load-driving capability. Simulation results show that, under the typical process corner (TT), with VDD = 3 V and T = 25 °C, the op-amp achieves an output swing of 0.2 V~2.8 V, a low-frequency gain of 102~118 dB, a PSRR of 90 dB at 60 Hz, overcurrent protection of ±25 mA, and a phase margin exceeding 48.8° with a 10 μF capacitive load. Across the entire supply voltage range, the static current remains below 150 μA, while maintaining a line regulation better than 150 μV/V and a load regulation better than 150 μV/mA. These results verify the feasibility of achieving both high drive capability and high stability under stringent power constraints, making the proposed design well-suited as a bandgap reference buffer stage for integrated accelerometers, with strong engineering practicality and potential for broad application. Full article

Wide-Bandgap (WBG) semiconductors—silicon carbide (SiC) and gallium nitride (GaN)— enable high-power-density conversion, but performance is limited by where heat is generated and how it is removed. This review links device-level loss mechanisms (conduction and switching, including output-capacitance hysteresis and dynamic on-resistance) to structure-driven hot spots within the ultra-thin (tens of nanometers) two-dimensional electron gas (2DEG) channel of GaN HEMTs and to thermal boundary resistance at layer interfaces. We compare wire-bondless package concepts—double-sided cooling, embedded packaging, and interleaved planar layouts—and survey system-level cooling that shortens the conduction path and raises heat-transfer coefficients. The impact on reliability is discussed using temperature-sensitive electrical parameters (e.g., on-state VDS, threshold voltage, drain leakage, di/dt, and gate current) for real-time junction-temperature estimation and compact electro-thermal RC models for remaining-useful-life prediction. Evidence from recent literature points to interface resistance in GaN-on-SiC as a primary bottleneck, while near-junction cooling and advanced packages are effective mitigations. We argue for integrated co-design—devices, packaging, electromagnetic interference (EMI)-aware layout, and cooling—together with interface engineering and health monitoring to deliver reliable, high-density WBG systems. Full article