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Effects of n-butyl amine incorporation on the performance of perovskite light emitting diodes
摘要： The efficiency of perovskite light emitting diodes (PeLEDs) is crucially limited by leakage current and nonradiative recombination. Here we introduce n-butyl amine (BA) to modulate the growth of perovskite films as well as improve the performance of PeLEDs, and investigate in details the effects of BA incorporation on the structural, optical, and electrical characteristics of perovskite films. The results indicate that BA would terminate the grain surface and inhibit crystal growth, leading to increased radiative recombination. However, BA overload would make the films loose and recreate shunt paths. The electrical detriment of BA overload outweighs its optical benefit. As a result, optimal PeLEDs can be obtained only with moderate BA incorporation.
关键词： optical and electrical characteristics,butyl amine,crystal growth,bulky organic cations,perovskite light emitting diodes
更新于2025-09-04 15:30:14
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[IEEE 48th European Solid-State Device Research Conference (ESSDERC 2018) - Dresden (2018.9.3-2018.9.6)] 2018 48th European Solid-State Device Research Conference (ESSDERC) - First and Second Order Piezoresistive Characteristics of CMOS FETs: Weak through Strong Inversion
摘要： Experimental results validate a continuous model describing the stress dependencies of CMOS FETs from weak through strong inversion. The model incorporates the significant impact of threshold voltage changes (through ni2) on the stress responses in all regions of operation and describes both first- and second-order longitudinal and traverse piezoresistive coefficients for PMOS and NMOS devices. Orthogonal differential pairs of MOSFETs can be utilized to directly measure the mobility component of the overall stress response.
关键词： threshold voltage,piezoresistive characteristics,CMOS FETs,stress dependencies,mobility variations
更新于2025-09-04 15:30:14
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CHARACTERISTICS OF MULTILAYERED METAMATERIAL STRUCTURES EMBEDDED IN FRACTIONAL SPACE FOR TERAHERTZ APPLICATION
摘要： This paper discusses the electromagnetic characteristics of a stratified metamaterial structure placed in fractional dimension space. Reflection and transmission coefficients for plane wave incident on multilayered structure in D-dimensional space are computed. Transfer matrix method is used to study the behaviour of different planer multilayered periodic metamaterial structures. The results are compared for integer and fractal dimensional spaces for both the cases of normal and oblique incidences. Classical results are recovered for integer dimensions. This work provides solution for examining the electromagnetic fields and waves in multilayered structures at fractal interfaces.
关键词： multilayered metamaterial structures,transfer matrix method,electromagnetic characteristics,fractional space,terahertz applications
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE Energy Conversion Congress and Exposition (ECCE) - Portland, OR, USA (2018.9.23-2018.9.27)] 2018 IEEE Energy Conversion Congress and Exposition (ECCE) - Novel monolithically integrated bidirectional GaN HEMT
摘要： Lateral chip architecture of GaN power semiconductors enables design of a monolithically integrated GaN HEMT featuring bidirectional blocking capability. The proposed bidirectional GaN HEMT allows for substantially reduced conduction losses in applications such as the multilevel T-type inverter which benefit from power semiconductors with bidirectional voltage blocking capability. In static and dynamic characterizations, the monolithically integrated bidirectional GaN HEMT exhibits similar switching and on-state behavior like conventional unidirectional GaN HEMTs.
关键词： bidirectional,T-type inverter,power semiconductor device,multilevel inverter,switching characteristics,Gallium Nitride,dynamic on-state resistance,HEMTs,integration,semiconductor
更新于2025-09-04 15:30:14
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NONLINEAR CHARACTERISTICS OF P-I-N DIODE CIRCUITS ANALYZED BY A PHYSICALLY BASED SIMULATION METHOD
摘要： Nonlinear characteristics of semiconductor devices play a key role in the performances of circuits, but their modelling is still a big challenge in circuit simulations nowadays. This paper explores modelling nonlinear characteristics of circuits containing semiconductor devices by presenting a modified physically based simulation method. A p-i-n diode microstrip circuit is taken as a sample, and its nonlinear characteristics, such as the power limiting, bistability, and forward recovery characteristics, are simulated and analysed. The applied method demonstrates its good capability and accuracy of modelling the nonlinear characteristics in the simulation, and moreover clarifies the underlying physical mechanisms. In contrast, the Advanced Design System (ADS) software, a popular circuit simulation program based on the equivalent circuit model, fails to reveal some of those nonlinear characteristics.
关键词： Nonlinear characteristics,microstrip circuit,p-i-n diode,semiconductor devices,physically based simulation method
更新于2025-09-04 15:30:14
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Study on the Physical and Leakage Current Characteristics of an Optimized High-k/InAlAs MOS Capacitor with a HfO2–Al2O3 Laminated Dielectric
摘要： High-k/n-InAlAs MOS capacitors are popular for the isolated gate of InAs/AlSb and InAlAs/InGaAs high-electron mobility transistors. In this study, a new kind of high-k/n-InAlAs MOS-capacitor with a HfO2–Al2O3 laminated dielectric was successfully fabricated using an optimized process. Compared with the traditional HfO2/n-InAlAs MOS capacitor, the new device has a larger equivalent oxide thickness. Two devices, with a HfO2 (8 nm)–Al2O3 (4 nm) laminated dielectric and a HfO2 (4 nm)–Al2O3 (8 nm) laminated dielectric, respectively, were studied in comparison to analyze the effect of the thickness ratios of HfO2 and Al2O3 on the performance of the devices. It was found that the device with a HfO2 (4 nm)–Al2O3 (8 nm) laminated dielectric showed a lower effective density of oxide charges, and an evidently higher conduction band offset, making its leakage current achieve a signi?cantly low value below 10?7 A/cm2 under a bias voltage from ?3 to 2 V. It was demonstrated that the HfO2–Al2O3 laminated dielectric with a HfO2 thickness of 4 nm and an Al2O3 thickness of 8 nm improves the performance of the high-k dielectric on InAlAs, which is advantageous for further applications.
关键词： C–V characteristics,high-k/InAlAs MOS-capacitor,HfO2–Al2O3 laminated dielectric,leakage current
更新于2025-09-04 15:30:14
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Simulation and comparative analysis of the DC characteristics of submicron GaN HEMTs for use in CAD software
摘要： Bearing in mind the requirements of design engineers, a nonlinear model is developed to simulate the temperature-dependent I–V characteristics of submicron high-electron-mobility transistors (HEMTs). Self- and ambient heating effects are incorporated into the model expression to cater for both the negative and positive conductance of the device, after the onset of the saturation current. It is shown that the accuracy of numerical models previously developed for metal–semiconductor field-effect transistors (MESFETs) deteriorates when simulating the I–V characteristics of gallium nitride (GaN) HEMTs, primarily due to the self-heating effects. The validity of the proposed model is checked for GaN HEMTs with gate length ( Lg ) ranging from 0.12 to 0.7 μm in the temperature range of T = 298 to T = 773 K. It is demonstrated that the proposed model simulates, with a good degree of accuracy, the output characteristics of such devices exhibiting negative conductance in the saturation region of operation. It is observed that, for devices exhibiting negative conductance in the saturation region, the peak transconductance ( gm ) occurs at a relatively higher negative gate bias while the peak value reduces with increasing ambient temperature. The root-mean-square errors reveal that the proposed model is better than other similar models reported in the literature, with an improvement varying from 17 to 50 % depending on the device characteristics.
关键词： Nonlinear model,Submicron HEMTs,Optimization,DC characteristics
更新于2025-09-04 15:30:14
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Pipeline leakage identification and localization based on the fiber Bragg grating hoop strain measurements and particle swarm optimization and support vector machine
摘要： A pipeline's safe usage is of critical concern. In our previous work, a fiber Bragg grating hoop strain sensor was developed to measure the hoop strain variation in a pressurized pipeline. In this paper, a support vector machine (SVM) learning method is applied to identify pipeline leakage accidents from different hoop strain signals and then further locate the leakage points along a pipeline. For leakage identification, time domain features and wavelet packet vectors are extracted as the input features for the SVM model. For leakage localization, a series of terminal hoop strain variations are extracted as the input variables for a support vector regression (SVR) analysis to locate the leakage point. The parameters of the SVM/SVR kernel function are optimized by means of a particle swarm optimization (PSO) algorithm to obtain the highest identification and localization accuracy. The results show that when the RBF kernel with optimized C and γ values is applied, the classification accuracy for leakage identification reaches 97.5% (117/120). The mean square error value for leakage localization can reach as low as 0.002 when the appropriate parameter combination is chosen for a noise‐free situation. The anti‐noise capability of the optimized SVR model for leakage localization is evaluated by superimposing Gaussian white noise at different levels. The simulation study shows that the average localization error is still acceptable (≈500 m) with 5% noise. The results demonstrate the feasibility and robustness of the PSO–SVM approach for pipeline leakage identification and localization.
关键词： pipeline leakage localization,method of characteristics (MOC),FBG hoop strain sensor,support vector regression (SVR),particle swarm optimization (PSO) algorithm,support vector machine (SVM)
更新于2025-09-04 15:30:14
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Dynamic Characteristics of Satellite Solar Arrays under the Deployment Shock in Orbit
摘要： Understanding the dynamic characteristics of solar arrays is important for satellite structural design and attitude control design. Considerable theoretical researches have been carried out towards this problem, but they have not been supported by actual orbit data from outer space yet. In this paper, the on-orbit vibration characteristic data of solar arrays under the deployment shock are measured by using vibration measurement apparatuses based on structural strain. With these valuable experimental data, more eigenfrequencies of the solar arrays in the microgravity environment are obtained, and the prediction that the vibration of solar arrays will have larger amplitude and longer decay time under vacuum conditions is veri?ed. Moreover, by comparing the eigenfrequency of main vibration under the space condition with that under the ground condition, the accurate value of the system damping ratio is gained, which has an important guideline signi?cant for the structural design of solar arrays.
关键词： solar arrays,deployment shock,on-orbit data,vibration measurement,dynamic characteristics
更新于2025-09-04 15:30:14
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Controlling shedding characteristics of condensate drops using electrowetting
摘要： We show here that ac electrowetting (ac-EW) with structured electrodes can be used to control the gravity-driven shedding of drops condensing onto ?at hydrophobic surfaces. Under ac-EW with straight interdigitated electrodes, the condensate drops shed with relatively small radii due to the ac-EW-induced reduction of contact angle hysteresis. The smaller shedding radius, coupled with the enhanced growth due to coalescence under EW, results in an increased shedding rate. We also show that the condensate droplet pattern under EW can be controlled, and the coalescence can be further enhanced, using interdigitated electrodes with zigzag edges. Such enhanced coalescence in conjunction with the electrically induced trapping effect due to the electrode geometry results in a larger shedding radius, but a lower shedding rate. However, the shedding characteristics can be further optimized by applying the electrical voltage intermittently. We ?nally provide an estimate of the condensate volume removed per unit time in order to highlight how it is enhanced using ac-EW-controlled dropwise condensation.
关键词： condensate drops,coalescence,shedding characteristics,hydrophobic surfaces,electrowetting
更新于2025-09-04 15:30:14