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Electrothermal performance of Resistive Random Access Memory (RRAM) composed of five different resistive switching oxides is studied numerically in this paper. Finite element method-based parallel computing simulator is employed to conduct the electrothermal simulation of both RRAM cell and array. Simulation results indicate that NiO and ZrO x RRAMs generate higher heat than HfO x , TiO x and ZnO x RRAMs, as their electric conductivity are higher in the same voltage. During the reset, ZnO x RRAM requires lower voltage to be transferred into high-resistance state due to its higher oxygen vacancy drift rate. The heat crosstalk problem in RRAM array is also investigated, which can decrease reliability during the reset of RRAM. Inactive cells can be transferred into high-resistance state unintentionally with stored information lost. In the same voltage, both HfO x and TiO x RRAMs are less affected by heat crosstalk due to their lower oxygen vacancy drift rate.

Techniques for “smart” 3D EM modeling are briefly recollected and described. By applying these techniques to a 3-layer printed dipole antenna, which is coaxially fed through finite sized reflector, the number of unknowns in MoM/SIE approach is reduced for an order of magnitude with negligible loss of accuracy. Such minimalistic model enabled full wave simulation of array of 28 by 28 elements at PC computer.

Computational study of atomically thin monolayer MoS2/WSe2 heterojunction with focus on carrier dynamics and thermal transport is performed by using finite-difference method to solve carrier transport equations and heat conduction equation. Carrier transport in the horizontal direction is in the micrometer scale, while in the vertical direction it is on the subnanometer scale. Carrier transport is modeled as diffusive transport in the horizontal direction with tunneling-assisted carrier recombination between two monolayers in the vertical direction as in the previous study. Band profile, quasi-Fermi level splitting, carrier distribution, and heat generation are investigated in detail. The heterojunction with high-doping concentration has larger current compared to that with low-doping concentration. Heat generation has two components which are due to the Joule heating and inelastic carrier recombination, respectively. The former is provided by the applied voltage, while the latter is from surrounding environment which acts as thermal reservoir. Since the heterojunction works very differently from the conventional p-n diode, it is compared to typical field-effect transistors due to similar device structures. The heat generation of the heterojunction is eight orders lower than that of typical nanoscale field-effect transistors because of its low-current density. Temperature increase in the heterojunction is also several orders of magnitude lower compared to typical nanoscale field-effect transistors.

This study demonstrates comparisons of power to failure for SiGe-based low-noise amplifiers by injecting high-power microwave pulses. A general equation was derived to calculate power to failure, which depends on pulse width and its duty cycle. Two types of silicon–germanium (SiGe) transistors were modeled, and their temperature distributions were simulated. The pulse thermal resistance, thermal capacitance, and breakdown temperature were calculated and determined. Results show that the power to failure of the two transistors depend on the number of slots, pulse thermal resistance, thermal capacitance, and breakdown temperature, although these transistors exhibit nearly similar structures. In addition, calculated and measured results show close correlations. A summary for calculating the power to failure of a type of SiGe transistor is provided.

The ancient paper craft of kirigami has recently emerged as a potential tool for the design of functional materials. Inspired by the kirigami concept, we propose a class of kirigami-based metamaterials whose electromagnetic functionalities can be switched between nonchiral and chiral states by stretching the predesigned split-ring resonator array. Single-band, dual-band, and broadband circular polarizers with reconfigurable performance are experimentally demonstrated with maximum circular dichroism of 0.88, 0.94, and 0.92, respectively. The underlying mechanism is explained and calculated via detailed analysis of the excited multipoles, including the electric, magnetic, and toroidal dipoles and quadrupole. Our approach enables tailoring the electromagnetic functionalities in kirigami patterns and provides an alternate avenue for reconfigurable optical metadevices with exceptional mechanical properties. A new twist on the Japanese art of origami has helped researchers achieve dynamic optical polarization switching for applications including lasers and biosensors. Metamaterials, substances engineered to manipulate radiation in non-natural ways—bending light around objects to make them appear invisible, for example—are normally impossible to re-configure after being fabricated. Liqiao Jing from Zhejiang University in Hangzhou, China, and colleagues have overcome this limitation by depositing periodic arrays of copper rings onto thin, foldable polymer sheets. By introducing small cuts and then stretching the sheets, the team created buckled, 3D surfaces with different symmetries to the original flat film. The rearranged atoms in the new structures enabled filtering of circularly polarized light, an effect which could be expanded to broadband frequencies by stacking two folded films on top of one another. An approach towards kirigami metamaterials with reconfigurable toroidal circular dichroism is presented. Inspired by the kirigami concept, kirigami-based chiral metamaterials are proposed to switch the electromagnetic performance between non-chiral and chiral states. When transforming the 2D metasurface to 3D kirigami patterns, the resonant modes exhibit gradually enhanced chiroptical response, from single-band, dual-band to broad-band functionalities.

In this paper, multilayer stepped impedance resonators (SIR) are proposed to design a dual frequency band filter. The center frequency of the proposed filter is 76 GHz and 94 GHz respectively. The design methodology has been investigated, demonstrated and verified. The filter has its compact size and fabricated by using our in-house multilayer BCB based MEMs fabrication technology with the minimum insertion loss 1.98 dB and 1.87 dB, respectively. The fractional bandwidth of 3 dB is 8.5 %and 6.7%, and the return loss of the two passbands is below 15dB. Simulated and measured results show close agreements. This filter offers advantages of easy integration with other active devices. It is suitable for three-dimensional integration of millimeter-wave and sub-Terahertz transceiver systems.

The frequency band ratio of dual-band microstrip grid array antennas (MGAA) is analyzed in this paper. Three dual-band MGAAs with different long side numbers are simulated to obtain the relationship between high and low operation frequency. Based on simulated results of the three antennas, high and low operation frequency ratio has a linear relationship with the low and high frequency resonant length ratio. By using the relationship, it is easy to estimate high and low band operation frequencies of dual-bandMGAAs.

This paper is devoted to characterizing the specific absorption rate (SAR) distribution of a human body model in a vehicle-based shelter in the presence of high-power intentional electromagnetic pulse (IEMP) radiation using a modified finite-difference time-domain (FDTD) method. The proposed method combines the FDTD(2, 4) method along with dielectric conformal techniques, where the updating equations of FDTD(2, 4) method are modified by introducing an effective dielectric constant and a new conductivity derived by area average of different dielectric regions including coating layer in nine spatial discrete cells. Numerical results show that our method even with coarse meshes has good agreements and efficiency comparing with the traditional FDTD method and CST simulation tool. Furthermore, the proposed method is applied to predict the SAR distribution of human body in a vehicle-based metallic shelter, where the peak SAR and average SAR are captured and compared in the presence of an IEMP with different polarizations and incident angles.

Adaptive process of finite-element method always needs to solve a set of linear systems repeatedly. This communication proposes an accurate and efficient domain decomposition method (DDM) based on a multilevel algorithm and a coarse-level correction strategy. Our developed algorithm facilitates the adaptive refinement process utilizing dynamic coarse-level correction, exploits the hierarchical feature of the refined systems through p-type multigrid method in subdomains, then solves the lowest order system through algebraic multigrid method in auxiliary and node-based spaces. The numerical results show that with this effective coarse-level correction, the residual errors introduced by adaptive refined systems can be eliminated quickly by the DDM. Besides, optimal performance in terms of simulation time is achieved, regardless of workload imbalances during the adaptive steps. Several large-scale electromagnetic problems are analyzed for accuracy as well as performance evaluation of the proposed method.

This paper presents a comprehensive investigation of the impedance characteristics of power distribution networks (PDNs) made of carbon nanotube through-silicon vias (CNT-TSVs). The equivalent circuit model of the CNT-TSV array is presented and validated through three-dimensional full-wave electromagnetic simulator up to 100 GHz. By virtue of the circuit model, the inductive properties of CNT-TSVs are characterized and compared for various physical parameters. Then, the PDN impedance characteristics of multiple stacked chip-PDNs with CNT-TSVs are captured and evaluated. It is found that the large CNT kinetic inductance may limit the PDN frequency range. Therefore, the fabrication of CNT-TSVs should be improved to increase the CNT density and reduce the contact resistance.

Electro-thermo-stress (ETS) failure of bonding wire array in a laterally diffused metal oxide semiconductor (LDMOS) field-effect transistor (FET)-based power amplifier during its high power’s ruggedness experiment is investigated in this paper. A special measurement system is at first set up to get reliability of the bonding wire array, where a microscope is used to capture its fractures. The temperature distribution of the LDMOSFET die surface and bonding wire array is also captured by a thermal infrared scanner to investigate the principle underlying the failure of ETS fractures. Simulation studies are also performed. The temperature distribution is closely related to the profiles of the bonding wire array. Numerical methods are employed to calculate the bonding wire array, and the temperature distributions are demonstrated by using our finite-element method code. It also works well in solving the transient temperature of the bond wire array with the stationary current and the heat source from the silicon region. The simulated thermal results agree well with the testing results. Finally, an improved LDMOS design in optimizing the bonding wire profile is proposed. This research can serve as a guide for the design of an LDMOS PA with enhanced reliability.

A novel electromagnetic bandgap (EBG) power plane etched with multiring complementary split ring resonators (CSRRs) is proposed for effectively suppressing simultaneous switching noise. Its equivalent circuit model is derived for predicting its bandwidth numerically. The measured insertion losses, i.e., S21-parameters of the two fabricated samples agree well with the simulated ones obtained by using the commercial software HFSS, respectively. It is shown that –40 dB suppression is achieved over an ultrawideband from 600 MHz to 13.26 GHz, when the two-ring CSRRs EBG power plane is used. While for four-ring CSRRs EBG case, the suppression level can be extended to –60 dB. Comparative studies are also performed on the signal integrity of a pair of differential transmission lines over L-bridge EBG with and without CSRRs, respectively, and similar performance is achieved.

A discontinuous Galerkin time-domain electric field integral equation method based on a marching-on-in-degree (MOD) scheme for simulating transient responses of perfect electric conductor objects is proposed in this letter. With the help of half-Rao–Wilton–Glisson spatial basis functions, we can simulate transient scattering responses of three-dimensional structures with either conformal or nonconformal meshes. The weighted Laguerre polynomials are chosen as temporal basis functions and implemented for the MOD scheme. Under such circumstances, the developed algorithm eliminates late-time instabilities and the limitation of Courant–Friedrichs–Lewy criteria. In addition, we adopt a fast-Fourier-transform-based blocking scheme to accelerate the temporal convolution of the MOD procedure. Some numerical examples are given to validate its stability and accuracy.

Computational study of nanopillar Si/poly (3,4-ethylene dioxythiophene):poly (styrenesulfonate) (PEDOT:PSS) heterojunction solar cell is performed by using finite element method to solve Poisson equation, drift-diffusion equations, and current continuity equations. The depletion width around the edge of the Si nanopillar is almost the same as that of planar junction, while the depletion width around the middle of the Si nanopillar is much wider than that of planar junction. As a result, besides the enhanced light absorption due to light trapping induced by nanopillar array as in previous studies, larger depletion region, which leads to higher electron-hole separation efficiency under light illumination, is another reason for short-circuit current increase of nanopillar solar cell. The reason for less open-circuit voltage of nanopillar solar cell is also clarified by explaining the reason for large dark current of the nanopillar solar cell compared to its planar structure counterpart as follows. The kink of the potential profile along the lines around the edge nanopillar leads to much sharper potential drop in the following depletion region, and results in greater hole density slope when the solar cells are forwarded biased. Since the Si/PEDOT:PSS behaves like a pn junction rather than a Schottky junction as clarified in the previous study and the PEDOT:PSS is much highly doped, nanopillar heterojunction has larger dark current than planar junction due to the larger hole diffusion current around Si nanopillar edge.

This paper presents an improved ultrawideband open-short de-embedding methodology. In contrast to the conventional measurement-based open-short de-embedding method, the presented method is a measurement-calculation hybrid method. First, the open and short de-embedding structures are measured, and the corresponding scattering parameters are obtained. Based on this, lumped-parameter models of the open and short de-embedding structures are established. Then, the established models are modified to solve the over de-embedding problem. Finally, the modified de-embedding structure models are implemented in the scattering parameters of device test structures to achieve ultrawideband de-embedding. To verify the proposed de-embedding method, the method is applied to active devices. The results before and after de-embedding are compared under multiple bias conditions. Furthermore, the results after de-embedding based on the conventional open-short method and the proposed method are compared up to 220 GHz. These results show that using the proposed method can achieve accurate ultrawideband de-embedding up to the terahertz frequency band.

In this paper, a compact passive equalizer for differential transmission channel is designed in TSV-based three-dimensional integrated circuits (3-D ICs). The compact size of the equalizer is achieved by a square shunt metal line. Three simplified odd-mode half circuit models are proposed for ground-signal-signal-ground (G-S-S-G) type TSVs, differential on-interposer interconnects, and differential channels, respectively. Those simplified models merely consist of frequency-independent elements and can accurately predict the differential insertion losses up to 20 GHz. Moreover, the electrical parameters of the proposed serial resistance-inductance (RL) type equalizers are derived from the system transfer functions and optimized by virtue of the time-domain inter-symbol interference cancellation technique. Further, the geometrical parameters of the RL equalizers are calculated by using a genetic algorithm based multi-objective optimization method. Finally, the performance of the designed RL equalizer is validated by both frequency- and time-domain simulations for 20 Gb/s high-speed differential signaling.

A differential probe-fed liquid crystal (LC)-based frequency tunable circular-ring patch antenna is presented. Besides, cavity model is extended to analyze the LC-based antenna for the differential operation. According to the cavity model, the permittivity and loss tangent of the LC are extracted from the measured differential reflection coefficients. Acceptable agreements among the measurement, simulation, and calculation for differential impedances, reflection coefficients, and radiation patterns are obtained and also validate the extraction method and model. More importantly, the extended cavity model can provide a deep physical insight into the LC-based antenna.

This paper presents a selection of research topics related to nano-electromagnetic compatibility (nano-EMC) issues in emerging carbon nanoelectronics. Carbon-based nano-interconnect modeling and analysis are first introduced. Then, the key techniques of carbon nanotube-filled through-silicon vias and carbon- based passive devices are discussed.

Three lossy filters with flat passband are proposed with substrate integrated waveguide (SIW) and microstrip resonators, designed with the non-uniform- Q method. By properly selecting the lower- Q -to-higher- Q ratio, the 0.2 dB bandwidth of the first filter is obtained to be 215 MHz (17% improvement), which is equivalent to a uniform unloaded Q -factor of 820 at the cost of additional in-band insertion loss (IL) of 0.5 dB, when compared with the full-SIW filters. Further, two techniques are utilised to adjust the Q -factor ratio. One method is implemented by mounting a resistor on each microstrip resonator to reduce its unloaded Q -factor. Then, the 0.2 dB passband of 243 MHz is achieved for the second filter, equivalent to a uniform unloaded Q -factor of 1420. The other method is realised by adjusting the Q -factor due to radiation loss of microstrip resonators. By changing the input/output feeding structures, the 0.2 dB bandwidth of the third filter is enhanced by 32%, at the cost of minimum IL increased by 0.9 dB. The occupied area of the proposed planar hybrid filters is reduced by 15-21% and the passband flatness is much better than that of the uniform- Q filter counterparts, as demonstrated by the simulated and measured results.

In this letter, a tunable multiband THz frequency-selective surface (FSS) is developed based on hybrid metal–graphene structures. The tunability characteristics are realized by inserting graphene strips between metal patches. The proposed FSS is studied based on the equivalent circuit model, which is validated against the simulation results using numerical methods. It is shown that the proposed hybrid structure has good performance in terms of bandwidth, gain, and tunability, and it is easy to be built as a potential competitor for THz applications.

Multiple-gate (MG) MOSFETs are promising candidates for next-generation integrated circuits technology. This paper presents the electrothermal characterization of three-type nanoscale MG MOSFETs, i.e., Π-gate, quadruple-gate (QG), and Ω-gate MOSFETs. Meanwhile, the temperature distribution of a real Ω-gate MOSFET with gradual channel width is also studied. Finite difference method (FDM) is adopted to solve the 3-D time-dependent heat conduction equations. The simulation results of the steady-state temperature distribution are validated against the commercial software COMSOL. Moreover, the transient temperature response of MG MOSFETs to different waveforms are also captured and compared.

This paper presents an L-2L de-embedding method for characterizing the electromagnetic properties of through-silicon-vias (TSVs) in 3-D ICs. To the best of our knowledge, this is the first paper that discusses the use of de-embedding method for multiport TSVs. The L-2L de-embedding structure and the analysis algorithm are first introduced. Then, the techniques for meeting two crucial requirements in accurately applying the method on multiport TSVs are proposed. To meet these two requirements, the de-embedding structure is designed to enhance the symmetry and the shielding TSVs are used to decrease the mutual admittance. The simulation results show that with the appropriate design, the shielding TSVs are able to greatly reduce the mutual admittance with little impact on TSVs and RDLs. Finally, the performance of the designed structures with and without shielding TSVs is examined via both full-wave simulation and the measurements. With the full-wave simulation results of TSVs as reference, it turns out that the de-embedding accuracy is significantly improved with the shielding TSVs. Moreover, the de-embedding results based on the measurements show good agreements with those of the simulation ones.

In this paper, a wideband model for on-chip interconnects with different shielding structures is proposed. In order to improve the performance of interconnects, solid ground, floating shields, and parallel ground shields are often employed in real applications. Based on the transmission line theory and electromagnetic wave theory, these three different shielding structures are analyzed and discussed. Also, many parasitic effects such as eddy current, skin effect, proximity effect, and substrate loss have been taken into consideration to improve the precision of the proposed model. It is shown that the simulated results of the model are in good agreement with the measured ones up to 110 GHz. The validity of the proposed model has been proven.

This letter proposes a novel hybrid finite-difference time domain (FDTD) method, which combines the full-wave FDTD (2, 4) method with a thin-wire model, a transmission-line equation, the Kirchhoff's law, and a two-port equivalent-circuit FDTD model, where antenna–cable coupling model and modified nodal analysis method are also implemented through a set of proper boundary conditions. In our method, both coaxial cable and thin-wire antenna are treated together without geometric meshing for full-wave simulation, and all the coupling processes among fields, transmission line equations, and circuit loads are carried out at the same time step. Such hybrid method is verified by comparing with both PSPICE and traditional FDTD method, and good agreements are obtained. Further, the proposed method is successfully applied to predict the transient electromagnetic responses of some complex transmission line networks in a vehicle-based metallic shelter.

Massively parallel simulation of large-scale electromagnetic problems is performed on a supercomputer using an in-house developed high-performance computing scheme together with a domain decomposition method, where parallel adaptive unstructured mesh generation is at first performed for modeling an arbitrary multiscale structure. The accuracy, speedup, as well as scalability of such parallel scheme are numerically tested and validated during its implementation for simulating electromagnetic environmental effects (E3) on a ship platform using the TianHe-II supercomputer. It is demonstrated that this method can overcome the convergence deficiency of conventional iterative solver. In addition, numerical experiments are also carried out to show its adaptability to the number of subdomains and object electrical size. It is believed that our developed solver can be further used for solving various E3 or electromagnetic compatibility problems for the design of many large-scale platforms.

Electrothermal study of the n-type SOI Fin-FETs at 50-nm node is performed by analytical method and numerical algorithm. The self-heating effects (SHE) are investigated and validated by commercial software and other published analytical solutions. Further, the time-dependent thermal conduction equation is solved to get the temperature response under different signal stresses, including step pulse, AC signal, and circuit-speed random stress which is mimicked by the pseudorandom binary sequence (PRBS) signal. It is found that the PRBS signal leads to a lower transient temperature peak in the n-type FinFET of an inverter than the AC signal due to the less logic transitions in the PRBS, and signal with higher frequency induces worse SHE. According to the temperature response, hot-carrier injection (HCI)-induced threshold voltage shift (TVS) in the n-type FinFET of an inverter is further captured. It is shown that TVS under PRBS stress is much lower than that the AC case with the same frequency due to less logic transitions in PRBS signal, and the TVS becomes more severe with the increase of signal frequency. Although the gradual-width structure for n-type FinFET leads to a much lower static temperature, it does not help a lot to improve dynamic temperature and TVS when the inverter is biased by AC or PRBS signals.

A versatile multiphysics simulation packet for investigating different resistive random acces memories (RRAMs) is developed in this paper. Heat transfer, electrical conduction, and ion migration in such heterogeneous structure are all taken into consideration. Three fully coupled partial differential equations are solved using our self-developed finite-difference algorithm, where Scharfetter–Gummel method is adopted to simulate ion migration with fast convergence achieved. This packet is validated in comparison with the commercial software based on the finite-element method. With its implementation, complete and clear pictures for crosstalk effect in vertically integrated RRAM are captured and compared, where the effects of key physical and geometrical factors are characterized and understood. Some useful suggestions to mitigate its unfavorable influences are given.

This study aims at studying thermal and stress breakdown of gallium nitride (GaN) high-electron-mobility transistors (HEMTs) with a high-power microwave (HPM) pulse injected. A thermal breakdown model, depending on its pulse width and duty cycle, is proposed at first, and an equation is derived for calculating power threshold when both geometrical and material parameters of transistor are known. A series of GaN HEMT-based power amplifiers is designed and measured by using one special HPM system for characterizing their power-to-failure values, and the calculated ones are then fitted for further determining failure temperature of GaN HEMT. Further, electrothermal simulation is performed for capturing temperature and stress distributions over the structure, where a few correlations are observed between the simulated and calculated results. Finally, the crack area in the field plate of GaN HEMT is also characterized experimentally.

This paper characterizes the frequency domain near-field coupling effects from complicated three-dimensional transmission lines, monopole/dipole radiators, and printed circuit boards (PCBs) located in a metallic rectangular cavity with an efficient iterative fast Fourier transform-accelerated integral-equation method. The simulation method combines the rectangular-cavity Green's functions with the frequency-domain electric field integral equation, which is further accelerated by the extension of adaptive integral method for rectangular cavities. By using this method, the near-field coupling effects and internal field distributions are captured and compared with independent references for various structures, including transmission lines, monopole/dipole radiators, and PCBs in rectangular cavities. Numerical results show that strong couplings do appear at multiple resonant frequencies of the structures. In addition, this method can be further employed to mitigate and suppress near-field coupling effects in the optimization of electromagnetic compatibility/interference designs.

A hybrid one-step leapfrog alternating-direction-implicit finite-difference time-domain (ADI-FDTD) method integrated with a thin wire algorithm is developed for simulating the near-field mutual coupling effects among multiple wire antennas on an electrically large warship platform, where induced surface current and electric field distributions are also captured. Its stability analysis, based on von Neumann method, is performed in a semi-analytical way and verified numerically. In order to demonstrate its accuracy and efficiency, the near-field mutual coupling effect between two thin wire antennas is at first investigated. Then, it is applied to accurately characterize complex electromagnetic environment effects on a warship with multiple thin wire antennas, and the results are compared with those obtained by the other commercial simulators.

A low-profile broadband bandpass frequency selective surface (FSS) with two rapid band edges is proposed in this paper for 5G near-field applications. The overall structure consists of three metallic layers, separated by two thin substrates with a thickness of 0.07λ. In addition, some centro-symmetric miniaturized slots are introduced in the middle metallic layer to further improve its stability and reduce its physical dimensions. A corresponding equivalent circuit model (ECM) is also proposed to better analyze the principles of the proposed FSS. Finally, an FSS prototype working at the center frequency of 27.5 GHz with a relative -3 dB bandwidth of 20.5% is fabricated and measured. More than 25 dB shielding effectiveness can be obtained out of the passband for a bandwidth of 1.46 GHz in this experiment. Both 3-D full-wave simulations and ECM results are in good agreement with the experimental results, having a maximum deviation of only 2.257% in the transmission zeros and poles. These results demonstrate that the proposed FSS is a good candidate for 5G near-field EMI shielding.

An active absorber with nearly zero static power consumption is proposed based on nonvolatile floating-gate graphene structure. Such absorber has almost no static power consumption benefited from the nonvolatile design. In such design, the central graphene can capture the tunneled electrons under the positive applied voltage, but cannot release these electrons after removing the voltage since it is electrically isolated from the external electrodes. Therefore, no extra power is needed to sustain the conductivity of graphene. Moreover, our proposed absorber exhibits an extremely strong absorption capacity. Even taking the strict condition for the bandwidth where all the absorptivity inside the bandwidth are larger than 90% as criterion, the proposed absorber provides more than 60 GHz absorption bandwidth which is twice larger than previous results. Furthermore, the proposed absorber shows high tolerance against large incidence angle ( $60^\circ $ ), different polarizations and nonideal factors of graphene. The results may promote various future nonvolatile absorber designs.

Heterojunction solar cells (HSCs) featuring half and full contact of poly(3,4-ethylenedioxythiophene):polystyrene (PEDOT:PSS) with pyramid-textured silicon (Si) were thoroughly compared via simulations and experiments, and the following conclusions have been reached: (1) The insufficient electrical passivation inherent to the half contact results in enormous decline in short-circuit current density (Jsc) and open-circuit voltage (Voc). (2) For the full-contact HSCs, Jsc is mainly dependent on the recombination at the rear interface. With tuning of the contact properties from both sides, calculated (experimental) efficiencies of 14.46%/16.89% (13.94%/16.21%) for the half-/full-contact HSCs were finally obtained. A superior power conversion efficiency (PCE) over 21% is further predicted by considering more optimal contact resistance as well as doping concentration of Si. Our findings clarify why textured-Si/PEDOT:PSS HSCs show Voc and PCE that are inferior to those of planar counterparts in previous reports...

In order to achieve tunable polarization rotation of the transmitted wave and controllable bandpass response simultaneously, a new graphene frequency selective surface (GFSS) is proposed for terahertz applications. The GFSS is built up by sandwiching a high-resistivity Si-substrate with a graphene patch array and a graphene sheet, both of which are electromagnetically biased. The configuration is analyzed by using an equivalent tensorial surface conductivity and transmission matrices of graphene structures, which is validated by full-wave simulations. The transmission coefficient, axial ratio, and polarization rotation angle of the bandpass GFSS are captured. An observable polarization rotation angle is obtained with a relatively large transmittance, which is superior to the graphene sheet and bandstop patch-type structures. The passband frequency is found to be not sensitive to the incident angle for either TE- or TM-polarized incidence, while it can be shifted from 1.6 to 2.2 THz with the polarization rotation angle varying from 24° to 16° by changing the chemical potential from 0.6 to 1 eV. When the applied magnetic field is set up to 3 T, the maximum rotation angle of polarization reaches up to 30° for TM incidence and 45° for TE incidence while the passband remains around 2 THz.

This paper deals with the fabrication of an inductorless wideband low-noise amplifier (LNA). The LNA includes two branches in parallel: a common-source (CS) path and a common-gate (CG) path. The CS path is responsible for providing enough power gain, while the CG path is used to achieve the input impedance matching. To eliminate the noise contribution of the CG path, the noise cancellation technique is applied. Therefore, the overall noise figure (NF) is improved. The phase mismatch between the two paths is also quantitatively analyzed to investigate its effect on gain and NF. The analytical results agree well with the simulation results. The LNA has been fabricated by a commercial 0.18- $\mu \text{m}$ CMOS process. The measurement results show that the LNA has achieved a maximum gain of 14.5 dB with 1.7-GHz 3-dB gain bandwidth and a minimum NF of 3 dB. The tested input 1-dB gain compression point (IP $_{{\text {1 dB}}}$ ) is −10.4 dBm at 1 GHz and the input third-order intercept point is 0.25 dBm. With 1.8-V supply, the LNA draws only 6-mA dc current.

Resistive random access memory (RRAM) is a promising candidate for next generation nonvolatile memory technology. In this paper, electrothermal simulation in 3-D RRAM arrays is performed by using our in-house developed finite difference algorithm, which is validated by comparing the simulated temperature distribution with its counterpart obtained by commercial software. Both crossbar RRAM array and vertical RRAM array are studied comprehensively with careful consideration of the temperature-dependent constitute parameters. Simulations show that the temperature and thermal crosstalk are sensitive to the size and shape of conductive filament, which can further limit the scaling potential of RRAM array through affecting its reliability, such as retention time, current leakage, and so on. Scaling behavior of 3-D RRAM array is studied, and optimization guidance for reducing thermal crosstalk is proposed. The fabrication inaccuracy resulted cell offset has also been examined for investigation of thermal crosstalk.

A lossy filter with flat passband and asymmetric response is proposed by using complex couplings. The complex coupling coefficients with positive and negative imaginary parts are realized with transmission lines loaded with series and shunt resistors, respectively. Design formulas are derived for the critical parameters. A filter prototype is developed at 4.97 GHz and substrate integrated waveguide resonators with unloaded $Q$ -factor of 450 are used. One transmission zero is located in its upper stopband. The 0.2-dB bandwidth of 279 MHz is achieved and the equivalent $Q$ -factor is about 1900. Good agreement is obtained among the synthesized, simulated, and measured results.

An RF CMOS model incorporating an improved substrate coupling network is developed. The proposed model focuses on characterizing the nonlinear phase of S12 when a transistor is under zero-bias condition. In addition, a corresponding parameter extraction technique of the model is proposed. To validate this model, a set of transistors fabricated in a commercial 90-nm CMOS process is investigated under multibias conditions. Comparison between measurement and calculation results shows that good agreement has been achieved, which indicates that the proposed model can accurately characterize the performance of transistors up to 66 GHz.

The harmonic spur characteristics of AlGaN/GaN power amplifiers (PA) at different temperatures are studied in this paper. Load-pull method is at first applied for the design of a C-band PA, which offers a peak output power of 48dBm (80W) with drain efficiency (DE) higher than 30%, and adjacent channel power ratio (ACPR) performance is less than −38 dBc. A temperature test chamber is used to provide desired temperature environment for measuring both power output and ACPR performance of the PA sample form low to high temperatures. Further, harmonic spur characteristics of the designed PA are measured, and it is shown that the harmonic spur power of PA increases with temperature in an approximately linear way.

Efficient evaluation of the scattered field radiated by transmission line cables is proposed in this paper. The common-mode (CM) equivalent circuit is applied to the transmission line cables for circuit simplification, then the transmission line model is implemented to obtain the CM current generated along the cables due to the plane wave excitation. Therefore, the scattered field is calculated from the obtained CM current and it is found that it is identical to the one obtained by the MoM method for the original transmission line circuit.

A finite element method (FEM)-based simulator with capability of parallel computing is developed for Multiphysics modeling and simulation of resistive random access memory (RRAM) array. The thermal crosstalk effects of a high density vertically integrated RRAM array are investigated. Simulation results show that severe reliability problem may occur during the reset process for RRAM cells even without applied voltage which can be transferred from low resistance state to high resistance state by mistake and hence lose their stored information.

In this paper, the electrothermal performance of large-scale resistive random access memory (RRAM) array is studied using an in-house developed parallel simulator. To realize the capability for parallel simulation, a high-performance computing scheme based on the mixed finite element method and finite volume method combining the domain decomposition method and J parallel adaptive unstructured mesh applications infrastructure is adopted. The performances, including accuracy and scalability of the in-house developed parallel simulator are accessed first. And then, the electrothermal characteristics of large-scale RRAM array are investigated using the simulator.

A generalized multi-conductor transmission (MTL) line model is developed for predicting electromagnetic wave coupling effects with multi-twisted bundle of twisted-wire pairs (MTB-TWP) above a ground with random non-uniform twisting. The twist pitches of the MTB-TWP are considered to be spatial stochastic functions. Then, the parametric equations of the non-uniform MTB-TWP are derived in their general form. In addition, the effect of non-synchronism during the twisting and incomplete terminal twist on the common mode (CM) and differential mode (DM) currents are investigated. Moreover, to imitate the real life disturbances, the twist pitches are assumed to follow Gaussian stochastic noises. After that, Monte Carlo simulations are carried out, hence, it is shown that the DM currents are very sensitive to the geometry of the twisting whereas the CM current is slightly effected. The MTL model is validated in comparison with MoM results and good agreements are obtained.

In this paper, a massively parallel multiphysics solver, based on an in-house massively parallel computing scheme for supercomputing, is developed for simulating large-scale antenna array and other 3-D structures, with domain decomposition method (DDM) also employed. During our simulation, frequency-domain electromagnetic fields are computed at first by solving the Helmholtz equation, and then the dissipated power is characterized, which is the heat source in the thermal co-simulation. New temperature profile can be obtained at the end of each iteration step, and they can be used to update all temperature-dependent parameters of the structure. This process is repeated until the temperature difference converge is achieved with a preset tolerance. The developed multiphysics solver is validated by comparing the results with that of commercial software. In particular, its speedup, scalability and efficiency are tested and examined.

Electromagnetic-thermal co-simulation of large antenna array on platform is performed using in-house enhanced finite element solver with massively parallel computing capability. It appropriately integrates both domain decomposition method (DDM) so as to solve very large complex matrix efficiently during the implementation of finite element procedure. Its massively parallel computing capability is examined on the supercomputer, where the antenna arrays of $16^{\ast}16$ operating at 2.5 GHz, together with their platform are simulated, respectively, and its accuracy is validated in comparison with the numerical result obtained by commercial software but just with small scale. The computational efficiency of such in-house developed solver can reach a speedup of 7.149 and strong scalability efficiency of 64.2% on 512 CPU cores of 32 computing nodes, and its speedup, scalability and efficiency are also examined. In particular, not only the radiation characteristics but also the surface temperature distribution of large antenna arrays are for the first time addressed in the high –power operating state, which directly support their reliability design.

This study presents the design of substrate-integrated slot antenna based on the TE20 mode. The conductance of a slot is calculated using a TE20 mode rectangular waveguide. A 94 GHz antenna is designed using benzocyclobutene for the package to validate the conductance calculations. Conductance is compared at different substrate-integrated waveguide thicknesses. The 94 GHz slot antenna has a gain of 7.2 dBi. Simulated and measured results have been compared. The antenna in package can be further interconnected and integrated with other active devices to demonstrate a three-dimensional integration.

A massively parallel electromagnetic field solver is developed for simulating large antenna array based on supercomputer using domain decomposition method (DDM) together with an in-house massively parallel computing scheme. The proposed solver is validated by comparing the simulated results with that obtained by commercial software. In particular, its speedup, scalability and efficiency are examined in the simulation of some typical large antenna arrays operating at different frequencies. It is numerically demonstrated that our parallel solver can reach a speedup of 7.149 and strong scalability efficiency of 89.36% on 512 CPU cores of 32 computing nodes. Further, a more challenging model is tested by using 1024 CPU cores of 64 computing nodes.