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Thermal management and characterization of high-power wide-bandgap semiconductor electronic and photonic devices in automotive applications
摘要： GaN-based high-power wide-bandgap semiconductor electronics and photonics have been considered as promising candidates to replace conventional devices for automotive applications due to high energy conversion efficiency, ruggedness, and superior transient performance. However, performance and reliability are detrimentally impacted by significant heat generation in the device active area. Therefore, thermal management plays a critical role in the development of GaN-based high-power electronic and photonic devices. This paper presents a comprehensive review of the thermal management strategies for GaN-based lateral power/RF transistors and light-emitting diodes (LEDs) reported by researchers in both industry and academia. The review is divided into three parts: (1) a survey of thermal metrology techniques, including infrared thermography, Raman thermometry, and thermoreflectance thermal imaging, that have been applied to study GaN electronics and photonics, (2) practical thermal management solutions for GaN power electronics, and (3) packaging techniques and cooling systems for GaN LEDs used in automotive lighting applications.
关键词： semiconductor,Raman thermometry,infrared thermography,high-power,automotive applications,LEDs,thermoreflectance thermal imaging,GaN,thermal management,wide-bandgap
更新于2025-09-04 15:30:14
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Implementing All-Optical New Reversible Gate using SOA-MZI Architecture
摘要： Reversible circuits have gained a lot of attention lately because of its remarkable property of dissipating lesser power as compared to irreversible circuits due to the fact that they do not lose information. Because of continuing revolution in VLSI technology transistor count and thus power dissipation has increased to such an extent that it has put a limit on packing density and performance of the circuits. To overcome these limits reversible logic has came into picture and various reversible logic gates such as Feynman gate, Fredkin gate, Toffoli gate, Peres gate etc has already been designed in optical domain. Semiconductor optical amplifier (SOA) based mach-Zehnder interferometer (MZI) plays a promising role in this field of ultra fast all-optical information processing because of its advantages like high speed, low power, easy of fabrication and fast switching time. Thus various circuits designed by these basic gates has been analysed in terms of cost parameters and it was seen that optical cost and delay of digital circuits is more than desired, as a result performance of system is rendered. Thus new gates are designed by various researchers that focus on improving cost and thus performance of the system. Studying all these modified gates and the digital circuits implemented in literature, an idea of New All-optical universal reversible gate has been proposed which will further improve the performance of digital circuits. Applications of this gate include the design of full adder, half adder, multiplexer and various other combinational circuits and also 13 standard Boolean expressions can be implemented with improved cost. Simulation of this new gate is done using VPI Photonics software.
关键词： Reversible Gates,Mach Zehnder Interferometer,All-Optical Communication,Semiconductor Optical Amplifiers
更新于2025-09-04 15:30:14
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Heat-Resistant Microporous Ag Die-Attach Structure for Wide Band-Gap Power Semiconductors
摘要： In this work, efforts were made to prepare a thermostable die-attach structure which includes stable sintered microporous Ag and multi-layer surface metallization. Silicon carbide particles (SiCp) were added into the Ag sinter joining paste to improve the high-temperature reliability of the sintered Ag joints. The use of SiCp in the bonding structures prevented the morphological evolution of the microporous structure and maintained a stable structure after high temperature storage (HTS) tests, which reduces the risk of void formation and metallization dewetting. In addition to the Ag paste, on the side of direct bonded copper (DBC) substrates, the thermal reliability of various surface metallizations such as Ni, Ti, and Pt were also evaluated by cross-section morphology and on-resistance tests. The results indicated that Ti and Pt diffusion barrier layers played a key role in preventing interfacial degradations between sintered Ag and Cu at high temperatures. At the same time, a Ni barrier layer showed a relatively weak barrier effect due to the generation of a thin Ni oxide layer at the interface with a Ag plating layer. The changes of on-resistance indicated that Pt metallization has relatively better electrical properties compared to that of Ti and Ni. Ag metallization, which lacks barrier capability, showed severe growth in an oxide layer between Ag and Cu, however, the on-resistance showed fewer changes.
关键词： wide band-gap semiconductor,die attachment,sinter joining
更新于2025-09-04 15:30:14
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Unidirectional absorption properties in a defective semiconductor-dielectric asymmetric triadic Cantor photonic crystal
摘要： It is well known that the defective asymmetric bilayer photonic crystal (PC), air/(DB)NA(BD)M/air, where A and B are dielectrics, D is lossy material, and N, M are stack numbers with N≠M, exhibits unidirectional absorption phenomena. In this work we theoretically study whether the defective asymmetric Cantor PC also exhibit the unidirectional optical property. The considered PC is the defective asymmetric Cantor PC, air/TCSN/A/TCSM/air, where TCSN is the N stage triadic Cantor structure composed of B and D; the semiconductor, n-InSb, is chosen as D. Our results show that their absorption spectra also exhibit unidirectional properties. Besides, the absorption peaks has defect mode depending on the defect layers just similar to the defect modes in the transmittance spectra of the usual symmetry photonic crystals.
关键词： photonic crystal,semiconductor,unidirectional absorption,defect mode
更新于2025-09-04 15:30:14
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Tuning the Crystal Packing and Semiconductor Electronic Properties of 7,7’-Diazaisoindigo by Side-Chain Length and Halogenation
摘要： In the last years, the 7,7’-diazaisoindigo has emerged as a promising building block for semiconductor materials. In this work, we have studied different electronic properties which can be related to the semiconducting character of a family of 7,7’-diazaisoindigo derivatives. Concretely, we have analyzed the role of halogen substituents and different-length side chains on these properties calculated by means of the Density Functional Theory. In total, sixteen halogenated and non-halogenated diazaisoindigo derivatives were investigated. Four of these compounds were also synthetized and their X-ray structures were employed as starting points for the calculation of crystal structure of the rest of the novel compounds. In general, high electron transfer rate constants and electron mobilites were calculated for the studied 7,7’-diazaisoindigo derivatives, especially for bromine derivatives and compounds with long-side chains. The origin of these high rate constants mainly resides in the strong electronic couplings found for diazaisoindigo crystals in the π-stacking direction.
关键词： 7,7’-diazaisoindigo,side chains,electron mobilities,halogen substituents,Density Functional Theory,semiconductor materials,electron transfer rate constants,π-stacking direction
更新于2025-09-04 15:30:14
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The Quantum Efficiency of Charge Transfer Competing Against Non-Exponential Processes: The Case of Electron Transfer from CdS Nanorods to Hydrogenase
摘要： Photoexcited charge transfer from semiconductor nanocrystals to charge acceptors is a key step for photon energy conversion in semiconductor nanocrystal-based light-harvesting systems. Charge transfer competes against relaxation processes within the nanocrystals, and this competition determines the quantum efficiency of charge transfer. The quantum efficiency is a critical design element in photochemistry, but in nanocrystal–acceptor systems its extraction from experimental data is complicated by sample heterogeneity and intrinsically non-exponential excited-state decay pathways. In this manuscript, we systematically explore these complexities using TA spectroscopy over a broad range of timescales to probe electron transfer from CdS nanorods to the redox enzyme hydrogenase. To analyze the experimental data, we build a model that quantifies the quantum efficiency of charge transfer in the face of competing, potentially non-exponential, relaxation processes. Our approach can be applied to calculate the efficiency of charge or energy transfer in any donor–acceptor system that exhibits non-exponential donor decay and any ensemble distribution in the number of acceptors provided that donor relaxation and charge transfer can be described as independent, parallel decay pathways. We apply this analysis to our experimental system and unveil the connections between particle morphology and quantum efficiency. Our model predicts a finite quantum efficiency even when the mean recombination time diverges, as it does in CdS nanostructures with spatially separated electron–hole pairs that recombine with power-law dynamics. We contrast our approach to the widely-used expressions for the quantum efficiency based on average lifetimes, which for our system overestimate the quantum efficiency. The approach developed here is straightforward to implement and should be applicable to a wide range of systems.
关键词： electron transfer,quantum efficiency,semiconductor nanocrystals,non-exponential processes,charge transfer,hydrogenase,CdS nanorods
更新于2025-09-04 15:30:14
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The Effects of Thermal Neutron Irradiation on Current-Voltage and Capacitance-Voltage Characteristics of Au/n-Si/Ag Schottky Barrier Diodes
摘要： To observe the neutron transmutation and displacement damage effects, Au/n-Si/Ag Schottky barrier diodes were exposed to thermal neutron irradiation. Irradiation induced changes in Schottky barrier height, saturation current, and donor concentration were investigated by using current-voltage (I-V) and capacitance-voltage (C-V) characteristics of the diodes. The irradiation for 10 s caused a little change in the Schottky diode parameters which were obtained from I-Vand C-V measurements. Observable changes in the parameters occurred after the second irradiation of 30 s duration. After the total dose, an increase in saturation current and barrier height inhomogeneties took into place and a decrease in carrier concentration was observed due to the carrier removal effect of thermal neutron-induced damages. Whereas the values of zero bias barrier height have little change after irradiations, the values of ideality factor increased after irradiations. The values of zero-bias barrier height for all diodes was also calculated from reverse bias current characteristics. After second dose, the values of zero-bias barrier height decreased for all diodes. The values of series resistance were determined by Cheung functions before and after irradiations. Before irradiations, the values were found between 2.10 kΩ and 2.76 kΩ. After second dose, the values of series resistance of all diodes decreased and were found between 1.59 kΩ and 2.20 kΩ. Furthermore, the proof of thermal neutron transmu- tation of elements in the devices was given via energy dispersive spectroscopy (EDS) mapping.
关键词： Semiconductor device radiation effects,Schottky diode,Electrical characterization,EDS mapping,Silicon,Thermal neutron irradiation
更新于2025-09-04 15:30:14
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Reference Module in Materials Science and Materials Engineering || SixGe1-x Bulk Crystals
摘要： Germanium–silicon (Ge1(cid:1)xSix) or silicon–germanium (SixGe1(cid:1)x) alloy, where x indicates the mole fraction of silicon, is a complete solid-solution semiconductor having the diamond cubic structure. The lattice parameters of the two elements differ by 4% and those of the solid solution closely follow Vegard's law from 0.564 (pure germanium) to 0.534 nm (pure silicon), while the bandgap changes from 0.72 (germanium) to 1.2 eV (silicon) according to composition. GeSi alloys are important for both microelectronic and optoelectronic devices and various functional materials because of the potential for bandgap and lattice parameter engineering they offer. The phase diagram of GeSi alloy is shown in Figure 1. The solidus and liquidus curves are widely separated. The equilibrium distribution coef?cient, k0 ? xs/xl (xs and xl being the solidus and liquidus concentration of silicon), is as large as 6 for germanium-rich solutions and about 2.2 at the average melting-point temperature of each element. Such a large gap between the liquidus and the solidus and the difference in the physical properties of the constituent elements, such as density, lattice parameter, and melting temperature, make the crystal growth of GeSi alloys very dif?cult. This article provides an outline of the applications and reviews the growth of bulk GeSi, discussing relevant problems, residual defects, impurities and dopants, and covers the structural properties of the alloys. The study of such alloys is also of interest from the fundamental view point of solidi?cation.
关键词： solid-solution semiconductor,crystal growth,microelectronic devices,optoelectronic devices,GeSi alloys
更新于2025-09-04 15:30:14
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In-doped As2Se3 thin films studied by Raman and X-ray photoelectron spectroscopies
摘要： Amorphous In-doped As2Se3 films with nominal indium contents x up to 7 at. % were prepared by thermal evaporation. Atomic force microscopy studies confirm the uniform film structure with a surface roughness near 5 nm, noticeably higher than for similarly prepared undoped As2Se3 film. X-ray photoelectron spectroscopy (XPS) studies enabled the chemical composition of the films to be examined. As follows from the XPS data, the In content in the film strongly decreases with the film depth. For films with x ≥ 2 at.%, Raman features attributed to transverse and longitudinal optical phonons of InAs are revealed in the Raman spectra as an evidence for the formation of InAs nanocrystallites in the As2Se3:In film under laser illumination.
关键词： X-ray photoelectron spectroscopy,amorphous,film,Raman scattering,atomic force microscopy,semiconductor nanocrystals
更新于2025-09-04 15:30:14
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Influence of Pb on structure, optical and electrical properties of Zn1-XPbXS semiconductor compounds at low temperatures
摘要： Zn1-XPbXS (x = 0–0.4 in steps of 0.1) ternary semiconductor samples have been prepared by co-precipitation method. The structural, optical and electrical studies have been carried out on all these samples to understand the influence of Lead on these properties. X-ray diffractograms showed that all Zn1-XPbXS samples have poly-crystalline nature with Hexagonal phase. The room temperature optical absorption studies revealed that energy gap decreases with increase of Pb in Zn1-XPbXS compounds. The temperature-dependent conductivity, measured in the range 300–4 K, led to understand that the conduction mechanisms at 60 K and 30 K are different. The activation energies evaluated at low (300–60 K) and very low temperature (60–30 K) regions are 38.03–32.58 meV and17.99–13.56 meV respectively. Activation energy and conductivity of Zn1-XPbXS samples increase with the increase of Pb. The samples exhibited low freezing temperature points indicating the possibility of their use in low temperature device applications.
关键词： Ternary semiconductor,Energy gap,Activation energy,Electrical conductivity
更新于2025-09-04 15:30:14