Showing papers on "Switching time published in 2019"

Performance Evaluation of High-Power SiC MOSFET Modules in Comparison to Si IGBT Modules

Abstract: The higher voltage blocking capability and faster switching speed of silicon-carbide (SiC) mosfet s have the potential to replace Si insulated gate bipolar transistors (IGBTs) in medium-/low-voltage and high-power applications. In this paper, a state-of-the-art commercially available 325 A, 1700 V SiC mosfet module has been fully characterized under various load currents, bus voltages, and gate resistors to reveal their switching capability. Meanwhile, Si IGBT modules with similar power ratings are also tested under the same conditions. From the test results, several interesting points have been obtained: different to the Si IGBT module, the over-shoot current of the SiC mosfet module increases linearly with the increase of the load current and it has been explained by a model of the over-shoot current proposed in this paper; the induced negative gate voltage due to the complementary device turn- off (crosstalk effect) is more harmful to the SiC mosfet module than the induced positive gate voltage during turn- on when the gate off-voltage is –6 V; the maximum dv / dt and di / dt (electromagnetic interference) during switching transients of the SiC mosfet module are close to those of the Si IGBT module when the gate resistance is larger than 8 Ω but the switching loss of the SiC mosfet module is much smaller; the switching losses of the Si IGBT module are greater than those of the SiC mosfet module even when the gate resistance of the former is reduced to zero. An accurate power loss model, which is suitable for a three-phase two-level converter based on SiC mosfet modules considering the power loss of the parasitic capacitance, has been presented and verified in this paper. From the model, a 96.2% efficiency can be achieved at the switching frequency of 80 kHz and the power of 100 kW.

A room-temperature organic polariton transistor

Abstract: Active optical elements with ever smaller footprint and lower energy consumption are central to modern photonics. The drive for miniaturization, speed and efficiency, with the concomitant volume reduction of the optically active area, has led to the development of devices that harness strong light–matter interactions. By managing the strength of light–matter coupling to exceed losses, quasiparticles, called exciton-polaritons, are formed that combine the properties of the optical fields with the electronic excitations of the active material. By making use of polaritons in inorganic semiconductor microcavities, all-optical transistor functionality was observed, albeit at cryogenic temperatures1. Here, we replace inorganic semiconductors with a ladder-type polymer in an optical microcavity and realize room-temperature operation of a polariton transistor through vibron-mediated stimulated polariton relaxation. We demonstrate net gain of ~10 dB μm−1, sub-picosecond switching time, cascaded amplification and all-optical logic operation at ambient conditions. Net gain of ~10 dB µm–1 and sub-picosecond switching time are shown at room temperature for optical transistors using polymers in a microcavity.

Active Gate-Driver With dv/dt Controller for Dynamic Voltage Balancing in Series-Connected SiC MOSFETs

Abstract: Series connection of individual semiconductors is an effective way to achieve higher voltage switches. However, the inherent unequal dynamic voltage sharing problem needs to be solved, even when well-matched gate drivers and semiconductors are used. A majority of the existing voltage balancing schemes are developed for slow-switching silicon (Si)-based semiconductors, and are also associated with a significant amount of additional losses in the control circuit or on the switches. In this paper, a novel method is proposed for balancing the dynamic voltages among series-connected silicon carbide (SiC) MOSFETs with high dv/dt rates. The method takes advantage of a small capacitor to provide additional current to the gate of the MOSFETs at turn- off , meaning the switching speed (and thus, the device voltage after turn- off ) is controlled. The proposed method generates negligible losses in the control circuit, and also does not significantly increase the switching losses of the semiconductors. Experimental results are provided to prove the effectiveness of the proposed voltage balancing scheme on two SiC MOSFETs inside a module connected in series. In order to do so, an active gate driver is designed embedding the active dv/dt control scheme as well as other essential functionalities needed for operation of SiC MOSFETs.

All-optical control of lead halide perovskite microlasers.

Abstract: Lead halide perovskites based microlasers have recently shown their potential in nanophotonics. However, up to now, all of the perovskite microlasers are static and cannot be dynamically tuned in use. Herein, we demonstrate a robust mechanism to realize the all-optical control of perovskite microlasers. In lead halide perovskite microrods, deterministic mode switching takes place as the external excitation is increased: the onset of a new lasing mode switches off the initial one via a negative power slope, while the main laser characteristics are well kept. This mode switching is reversible with the excitation and has been explained via cross-gain saturation. The modal interaction induced mode switching does not rely on sophisticated cavity designs and is generic in a series of microlasers. The switching time is faster than 70 ps, extending perovskite microlasers to previously inaccessible areas, e.g., optical memory, flip-flop, and ultrafast switches etc. Lead halide perovskite lasers have great potential as microscale organic light sources, but dynamic tuning has yet to be achieved. Here, Zhang, Fan et al. investigate how nonlinear modal interactions enable ultrafast mode switching with crossgain saturation.

Ultrafast and energy-efficient all-optical switching with graphene-loaded deep-subwavelength plasmonic waveguides

Abstract: All-optical switches have attracted attention because they can potentially overcome the speed limitation of electric switches. However, ultrafast, energy-efficient all-optical switches have been challenging to realize due to the intrinsically small optical nonlinearity in existing materials. As a solution, we propose graphene-loaded deep-subwavelength plasmonic waveguides (30 nm x 20 nm). Thanks to extreme light confinement, we have significantly enhanced optical nonlinear absorption in graphene, and achieved ultrafast all-optical switching with a switching energy of 35 fJ and a switching time of 260 fs. The switching energy is four orders of magnitudes smaller than that in previous graphene-based devices and is the smallest value ever reported for any all-optical switch operating at a few picoseconds or less. This device can be efficiently connected to conventional Si waveguides and employed in Si photonic integrated circuits. We believe that this graphene-based device will pave the way towards on-chip ultrafast and energy-efficient photonic processing.

A Novel Active Gate Driver for Improving Switching Performance of High-Power SiC MOSFET Modules

Abstract: Featuring higher switching speed and lower losses, the silicon carbide mosfet s (SiC mosfet s) are widely used in higher power density and higher efficiency power electronic applications as a new solution. However, the increase of the switching speed induces oscillations, overshoots, electromagnetic interference (EMI), and even additional losses. In this paper, a novel active gate driver (AGD) for high-power SiC mosfet s is presented to fully utilize its potential of high-speed characteristic under different operation temperatures and load currents. The principle of the AGD is based on drive voltage decrement during the voltage and current slopes since high dV/dt and dI/dt are the source of the overshoots, oscillations, and EMI problems. In addition, the optimal drive voltage switching delay time has been analyzed and calculated considering a tradeoff between switching losses and switching stresses. Compared to conventional gate driver with fixed drive voltage, the proposed AGD has the capability of suppressing the overshoots, oscillations, and reducing losses without compromising the EMI. Finally, the switching performance of the AGD was experimentally verified on 1.2 kV/300 A and 1.7 kV/300 A SiC mosfet s in double pulse test under different operation temperatures and load currents. In addition, an EMI discussion and cost analysis were realized for AGD.

Spin-Orbit Torque Switching of a Nearly Compensated Ferrimagnet by Topological Surface States.

Abstract: charge-spin conversion and ii) the speed of SOT switching. Generally, SOT in a magnetic layer originates from the spin current injection from the adjacent layer with strong spin-orbit coupling (SOC). The charge-spin conversion efficiency is vital and can be quantified as the θ = / SHE s 3D e 3D J J (dimensionless) or q J J t θ = = / / ICS s 3D e 2D SHE s , where s 3D J represents the 3D spin current density; e 3D J and e 2D J represent the 3D and 2D electric (charge) current density, respectively; and t s represents the effective SOC thickness. In the conventional SOC materials such as HMs, in principle, the θ SHE should be much less than 1, which limits their potential applications in the ultralow power magnetization manipulation. [4] In topological insulators (TIs), SOC from topologically protected surface states, where the spin and orbital angular momenta are locked (spin-momentum locking [5-7]), gives rise to a very large θ SHE [8-12] (or q ICS) and the resulting ultralow switching current density [13-15] at low temperature. Recently, several works have reported the room-temperature SOT switching by TIs, [16-19] which opens the door for the applications of topological insulators. However, there are fundamental limitations of FMs: the low switching speed (≈ns) and the stray-field interaction, which limit the operation speed and the density of magnetic memory, respectively. Antiferromagnets (AFMs) can afford the THz ultrafast spin dynamics; [20] however, AFMs produce zero stray field and zero spin polarization because of the opposite coupled spin lattices from the same element, which makes it difficult to detect the antiferromagnetic order efficiently. [21] Ferrimagnets have two antiferromagnetically coupled spin sublattices, and the contribution of each spin sublattice to their properties can be tuned by the composition or temperature. At the magnetic compensation point, ferrimagnets show similar properties of AFMs, such as ultrafast spin dynamics, [22,23] while the detection is still feasible because of the different responses to the optical or electrical excitations from two spin sublattices. [23-25] Here, we combine TIs [Bi 2 Se 3 and (BiSb) 2 Te 3 ] with nearly compensated ferrimagnets [Gd x (FeCo) 1−x ], and investigate the room-temperature SOT in TI/Gd x (FeCo) 1−x systems. By changing the composition of Gd x (FeCo) 1−x , we can tune the net magnetic moment and the dominated spin sublattice (CoFe-rich and Gd-rich). The robust room-temperature SOT switching Utilizing spin-orbit torque (SOT) to switch a magnetic moment provides a promising route for low-power-dissipation spintronic devices. Here, the SOT switching of a nearly compensated ferrimagnet Gd x (FeCo) 1−x by the topological insulator [Bi 2 Se 3 and (BiSb) 2 Te 3 ] is investigated at room temperature. The switching current density of (BiSb) 2 Te 3 (1.20 × 10 5 A cm −2) is more than one order of magnitude smaller than that in conventional heavy-metal-based structures, which indicates the ultrahigh efficiency of charge-spin conversion (>1) in topological surface states. By tuning the net magnetic moment of Gd x (FeCo) 1−x via changing the composition, the SOT efficiency has a significant enhancement (6.5 times) near the magnetic compensation point, and at the same time the switching speed can be as fast as several picoseconds. Combining the topological surface states and the nearly compensated ferrimagnets provides a promising route for practical energy-efficient and high-speed spintronic devices. Topological Spintronics Spintronic devices have been considered as one of the promising candidates for the next-generation memory and logic devices, and spin-orbit torque (SOT) provides an efficient way to manipulate the magnetic moment by electrical method with ultralow power dissipation and ultrafast operating speed. [1-3] Beyond previous studies of SOT switching based on conventional heavy metal/ferromagnet (HM/FM) heterostructures, two crucial issues need to be resolved: improving: i) the efficiency of

Ultrafast measurements of polarization switching dynamics on ferroelectric and anti-ferroelectric hafnium zirconium oxide

Abstract: The ultrafast measurements of polarization switching dynamics on ferroelectric (FE) and antiferroelectric (AFE) hafnium zirconium oxide (HZO) are studied. The transient current during the polarization switching process is probed directly on the nanosecond scale. The switching time is determined to be as fast as 10 ns to reach fully switched polarization with characteristic switching times of 5.4 ns for FE HZO and 4.5 ns for AFE HZO by the nucleation limited switching model. The limitation by the parasitic effect on capacitor charging is found to be critical in the correct and accurate measurements of intrinsic polarization switching speed of HZO.

First Direct Measurement of Sub-Nanosecond Polarization Switching in Ferroelectric Hafnium Zirconium Oxide

Abstract: In this work, we report on an ultrafast direct measurement on the transient ferroelectric polarization switching in hafnium zirconium oxide with a crossbar metal-insulator-metal (MIM) structure. A record low sub-nanosecond characteristic switching time of 925 ps was achieved, supported by the nucleation limited switching model. The impact of electric field, film thickness and device area on the polarization switching speed is systematically studied.

State of the Art and Perspectives on Silicon Photonic Switches.

Abstract: In the last decade, silicon photonic switches are increasingly believed to be potential candidates for replacing the electrical switches in the applications of telecommunication networks, data center and high-throughput computing, due to their low power consumption (Picojoules per bit), large bandwidth (Terabits per second) and high-level integration (Square millimeters per port). This review paper focuses on the state of the art and our perspectives on silicon photonic switching technologies. It starts with a review of three types of fundamental switch engines, i.e., Mach-Zehnder interferometer, micro-ring resonator and micro-electro-mechanical-system actuated waveguide coupler. The working mechanisms are introduced and the key specifications such as insertion loss, crosstalk, switching time, footprint and power consumption are evaluated. Then it is followed by the discussion on the prototype of large-scale silicon photonic fabrics, which are based on the configuration of above-mentioned switch engines. In addition, the key technologies, such as topological architecture, passive components and optoelectronic packaging, to improve the overall performance are summarized. Finally, the critical challenges that might hamper the silicon photonic switching technologies transferring from proof-of-concept in lab to commercialization are also discussed.

Flexible PCB-Based 3-D Integrated SiC Half-Bridge Power Module With Three-Sided Cooling Using Ultralow Inductive Hybrid Packaging Structure

Abstract: Silicon carbide (SiC) devices are capable of high switching speeds and also enable high switching frequency in power electronic converters. However, this feature poses substantial challenges to packaging, especially limiting the loop inductance. The traditional wire-bonding packaged power module has large parasitic inductance, which will cause voltage overshoot, oscillation, parasitic turn-on, and EMI issues. In order to reduce the parasitic inductance, this paper proposes a flexible printed circuit board (FPCB) based full SiC half-bridge power module with a novel low inductive hybrid packaging structure and three-dimensional (3-D) integration method. This hybrid packaging structure has an ultrathin FPCB substrate stacked on a direct bonding copper (DBC) substrate, which forms a multilayer 3-D power loop. The SiC chips are soldered on the DBC substrate for good thermal dissipation through a cavity in the FPCB substrate. After power loop optimization, the power loop inductance of a 1200-V/120-A SiC power module is only 0.79 nH. The power module consists of three submodules, which are connected by the bendable FPCB substrate. The bendable power module enables maximum utilization of 3-D space. The gate drive, decoupling capacitors, and dc-link capacitors are also integrated and 3D-structured using rigid-flexible PCBs. Moreover, the cooling system is a high-efficiency three-sided cooling structure for the bendable power module. The simulation results show that the three-sided cooling structure reduces the heatsink volume by 50%. Applying this method, the converter can be designed as a system-in-package and a 3D-structured compact system. The power density of a 20-kW three-phase inverter will reach 19.3 kW/L based on this power module. In this paper, the 1200-V/120-A power module fabrication and assembly processes are given. Finally, the static and dynamic experimental comparisons are done for a commercial power module and the proposed power module. The experiment results show that the voltage overshoot of the proposed module reduces about 5.8 times and are consistent with the simulation results. Meanwhile, the proposed power module switching speed is 1.8 times faster than the commercial module under zero external gate resistors and the switching loss can reduce by about 60%.

Evaluation of Switching Loss Contributed by Parasitic Ringing for Fast Switching Wide Band-Gap Devices

Abstract: Parasitic ringing is commonly observed during the high-speed switching of wide band-gap (WBG) devices. Additional loss contributed by parasitic ringing becomes a concern especially for high switching frequency applications. This paper investigates the effects of parasitic ringing on the switching loss of WBG devices in a phase-leg configuration. An analytical switching loss model considering parasitics in power devices and application circuit is derived. Two switching commutation modes, gate drive dominated mode and power loop dominated mode, are investigated, respectively, and the switching loss induced by damping ringing is identified. It is found that this portion of the loss is at most the energy stored in parasitics, which always exists regardless of the switching speed and parasitic ringing. Therefore, with the given WBG device in the specific application circuit, damping more severe parasitic ringing during faster switching transient would not introduce higher switching loss. Additionally, the extra switching loss induced by resonance among parasitics and crosstalk is investigated. It is observed that severe resonance and its resultant over-voltage during the turn- on transient worsen the crosstalk, causing large shoot-through current and excessive switching loss. The theoretical analysis has been verified by the double pulse test with a 1200-V/50-A SiC-based phase-leg power module.

A Low Gate Turn-OFF Impedance Driver for Suppressing Crosstalk of SiC MOSFET Based on Different Discrete Packages

Abstract: Because of higher switching speed of silicon carbide MOSFET, the crosstalk in a phase-leg configuration will be more serious, which hinders the increase of switching frequency and lowers the reliability of the power electronic equipment. The displacement current of the gate–drain capacitor and the voltage drop on the common-source inductors can induce the crosstalk. In order to suppress the crosstalk, this paper proposes a novel gate driver, in which two additional capacitors are added to create the low turn-off gate impedance. With this proposed driver, the common-source parasitic inductor can be decoupled from the gate loop and the displacement current of the gate–drain capacitor can be bypassed. In addition, the operating principle and the parameters design are also analyzed. Finally, the crosstalk in the non-Kelvin package and the Kelvin package are tested by experiments, the validity of the analysis and the effectiveness for suppression the crosstalk are proved as well.

The ultimate switching speed limit of redox-based resistive switching devices.

Abstract: In contrast to classical charge-based memories, the binary information in redox-based resistive switching devices is decoded by a change of the atomic configuration rather than changing the amount of stored electrons. This offers in principle a higher scaling potential as ions are not prone to tunneling and the information is not lost by tunneling. The switching speed, however, is potentially smaller since the ionic mass is much higher than the electron mass. In this work, the ultimate switching speed limit of redox-based resistive switching devices is discussed. Based on a theoretical analysis of the underlying physical processes, it is derived that the switching speed is limited by the phonon frequency. This limit is identical when considering the acceleration of the underlying processes by local Joule heating or by high electric fields. Electro-thermal simulations show that a small filamentary volume can be heated up in picoseconds. Likewise, the characteristic charging time of a nanocrossbar device can be even below ps. In principle, temperature and voltage can be brought fast enough to the device to reach the ultimate switching limit. In addition, the experimental route and the challenges towards reaching the ultimate switching speed limit are discussed. So far, the experimental switching speed is limited by the measurement setup.

A Low-Power and High-Speed Voltage Level Shifter Based on a Regulated Cross-Coupled Pull-Up Network

Abstract: In this brief, a fast and very low power voltage level shifter (LS) is presented. By using a new regulated cross-coupled (RCC) pull-up network, the switching speed is boosted and the dynamic power consumption is highly reduced. The proposed LS has the ability to convert input signals with voltage levels much lower than the threshold voltage of an MOS device to higher nominal supply voltage levels. The presented LS occupies a small silicon area owing to its very low number of elements and is ultra-low-power, making it suitable for low-power applications such as implantable medical devices and wireless sensor networks. Results of the post-layout simulation in a standard 0.18- ${\mu }\text{m}$ CMOS technology show that the proposed circuit can convert up input voltage levels as low as 80 mV. The power dissipation and propagation delay of the proposed LS for a low/high supply voltages of 0.4/1.8 V and input frequency of 1 MHz are 123.1 nW and 23.7 ns, respectively.

Switching dynamics of ferroelectric HfO2-ZrO2 with various ZrO2 contents

Abstract: To explore the effect of the ZrO2 content on the switching speed of ferroelectric HfO2-ZrO2 (FE-HZO), we demonstrate 10 nm FE-HZO capacitors fabricated with 5:5, 6:4, and 7:3 HfO2 and ZrO2 atomic-layer-deposition-cycling ratios. The FE-HZO devices show high remanent polarization (Pr) of 26, 20, and 11 μC/cm2 for the 5:5, 6:4, and 7:3 samples, respectively. The FE-HZO capacitors with lower ZrO2 contents show increasing coercive fields, which intuitively seem to increase switching difficulty. However, the FE-HZO devices with 50 mol. %, 40 mol. %, and 30 mol. % ZrO2 contents show decreasing switching times for 80% polarization, namely, 1.2, 0.9, and 0.7 μs, respectively. Because of the polycrystalline nature of FE-HZO, the distribution of local fields in the film is analyzed based on the inhomogeneous field mechanism model. The results show that the FE-HZO devices with lower ZrO2 contents have higher active fields and less uniform distribution of local fields. However, time constants for the 5:5, 6:4, and 7:3 samples decrease dramatically, being 137, 98, and 14 ps, respectively. These results unveil the distribution of the local fields in FE-HZO with varying ZrO2 contents and are helpful for understanding and optimizing the switching dynamics of FE-HZO for non-volatile memory applications.

Ultrafast All-Optical Light Control with Tamm Plasmons in Photonic Nanostructures

Abstract: Ultrafast all-optical modulators are crucial parts of prospective photonic devices. A number of plasmonic and dielectric nanostructures were nominated as candidates for integrated all-optical circuits. The key principle in the design of such devices is to engineer artificial optical resonances to increase the magnitude of modulation or to change the characteristic switching time. The major drawback is that the manufacturing becomes rather sophisticated. Here, we propose a method to tailor the ultrafast response of photonic crystal–metal nanostructures by employing a spectral shift of the Tamm-plasmon resonance. We show that for the absorbed pump fluence of 6 pJ reflectance of the sample at the near-infrared probe wavelength in the vicinity of the Tamm-plasmon resonance changes 25× stronger as compared with a bare metal film. Additionally, we show that by choosing a proper wavelength around the resonance a background-free reflectance modulation can be achieved. The characteristic pulse-limited switching ti...

Designer photonic dynamics by using non-uniform electron temperature distribution for on-demand all-optical switching times

Abstract: While free electrons in metals respond to ultrafast excitation with refractive index changes on femtosecond time scales, typical relaxation mechanisms occur over several picoseconds, governed by electron-phonon energy exchange rates. Here, we propose tailoring these intrinsic rates by engineering a non-uniform electron temperature distribution through nanostructuring, thus, introducing an additional electron temperature relaxation channel. We experimentally demonstrate a sub-300 fs switching time due to the wavelength dependence of the induced hot electron distribution in the nanostructure. The speed of switching is determined by the rate of redistribution of the inhomogeneous electron temperature and not just the rate of heat exchange between electrons and phonons. This effect depends on both the spatial overlap between control and signal fields in the metamaterial and hot-electron diffusion effects. Thus, switching rates can be controlled in nanostructured systems by designing geometrical parameters and selecting wavelengths, which determine the control and signal mode distributions. Here, the authors engineer a non-uniform electron temperature distribution through nanostructuring and demonstrate a sub-300 fs switching time. This can assist in the design of nanostructures for nonlinear optics, hot carrier extraction and photocatalysis

Ultracompact ultrafast-switching-speed all-optical 4 × 2 encoder based on photonic crystal

Abstract: A novel two-dimensional photonic-crystal-based all-optical encoder was designed, tested, and optimized. The structure is built on a linear square-lattice photonic crystal platform. An ultracompact, simple design occupying an area of only 128.52 μm2 is constructed, 50 % smaller than the smallest design known to date. Ultrafast switching speed with the lowest known delay time is achieved. The proposed design consists of one ring resonator with cylindrical silicon rods suspended in air. No auxiliary or bias input is required for its operation. The proposed platform is not sensitive to the applied input phase shift. Finite-difference time-domain and plane-wave expansion methods were used to analyze the structure and optimize the radius of the rods at 1.525 µm, with radius of the inner rods of 0.19a, for successful operation, resulting in ultrafast switching speed of 10 THz and shorter delay time reaching 0.1 ps. This maximum switching speed is two times faster than recent literature reports. The contrast ratio is calculated to reach an acceptable record of 7.1138 dB. The trade-off between the switching speed and contrast ratio was also examined.

An Improved Active Crosstalk Suppression Method for High-Speed SiC MOSFETs

Abstract: Silicon carbide (SiC) power electronic devices feature the advantages of fast switching speed, low conduction loss, and reliable operation in high temperature environment, etc. Due to the differences of parasitic parameters and threshold voltage between SiC mosfet s and Si mosfet s, crosstalk problem is easy to be triggered when SiC mosfet s are applied to bridge topologies. In this paper, the crosstalk effect with different parasitic parameters of SiC mosfet s is firstly analyzed, and then an improved active crosstalk suppression method for high-speed SiC mosfet s is proposed. By using the proposed method, when the crosstalk occurs, the crosstalk voltage will be decreased by reducing the equivalent gate resistance and increasing the equivalent gate-source capacitance in an active way. Consequently, the crosstalk problem can be suppressed without affecting the switching speed. To verify the effectiveness of the proposed method, a prototype of a buck–boost converter is built and the proposed modified gate driver is applied to the half-bridge topology. Comparative experimental study is conducted and the crosstalk voltage is analyzed. The experimental results verify that effective crosstalk suppression is achieved.

Sub-nanosecond spin-torque switching of perpendicular magnetic tunnel junction nanopillars at cryogenic temperatures

Abstract: Spin-transfer magnetic random access memory devices are of significant interest for cryogenic computing systems where a persistent, fast, low-energy consuming, and nanometer scale device operating at low temperature is needed. Here, we report the low-temperature nanosecond duration spin-transfer switching characteristics of perpendicular magnetic tunnel junction (pMTJ) nanopillar devices (40–60 nm in diameter) and contrast them to their room temperature properties. Interestingly, the characteristic switching time decreases with temperature, with the largest reduction occurring between room temperature and 150 K. The switching energy increases with decreasing temperature, but still compares very favorably with other types of spin-transfer devices at 4 K, with <300 fJ required per switch. Write error rate (WER) measurements show highly reliable switching with WER ≤ 5 × 10–5 with 4 ns pulses at 4 K. Our results demonstrate the promise of pMTJ devices for cryogenic applications and show routes to further device optimization.

Polarization switching kinetics of the ferroelectric Al-doped HfO2 thin films prepared by atomic layer deposition with different ozone doses

Abstract: Ferroelectric switching kinetics of the Al-doped HfO2 (Al:HfO2) thin films prepared by the atomic layer deposition process were investigated by varying the dose time of oxygen precursor (O3). When the O3 dose time was reduced to 3 s, the Al:HfO2 films exhibited an enhanced remnant polarization (2Pr) of 10.2 μC/cm2 due to the suppression of the monoclinic phase and the increase in the ratio of oxygen vacancy. Double-pulse switching and the Kolmogorov–Avrami–Ishibashi model were used to obtain detailed quantitative information on the switching kinetics of the Al:HfO2 films. The estimated values of switching time and activation energy showed the strong dependence of O3 dose. This suggests that the O3 dose condition can be a key control parameter to modulate the ferroelectric polarization switching dynamics of the Al:HfO2 thin films.

Compressed Sensing Method for IGBT High-Speed Switching Time On-Line Monitoring

Abstract: Condition monitoring (CM) has been considered as a promising technique to improve the reliability of insulated gate bipolar transistors (IGBTs). Among various condition parameters, switching time is a good health status indicator to detect IGBT failures. However, on-line monitoring of the IGBT high-speed switching time is still difficult in practice due to the requirement of the extremely high sampling rate for signal acquisition. To overcome the technical difficulty, this paper provides an innovative compressed sensing (CS) method to achieve equivalent sampling performance for high-speed IGBT switching time monitoring with a lower sampling rate. By utilizing the sparse characteristics of an IGBT switching signal, the sampling rate in the CS method could be far less than the traditional Nyquist sampling rate. To clarify the method, the CM mechanism using IGBT switching time is first analyzed. Then, three key points in the CS method are studied, i.e., the selection of sparsifying basis, the design of a measurement matrix, and the implementation of a reconstruction algorithm. Finally, experiments are carried out to investigate the performance of the CS method for on-line CM. Experimental results show that the IGBT turn- off time at different temperatures can be accurately monitored with a highly compressed sampling rate, which validates the feasibility and effectiveness of the proposed method.

CMOS-compatible, piezo-optomechanically tunable photonics for visible wavelengths and cryogenic temperatures.

Abstract: We demonstrate a platform for phase and amplitude modulation in silicon nitride photonic integrated circuits via piezo-optomechanical coupling using tightly mechanically coupled aluminum nitride actuators. The platform, fabricated in a CMOS foundry, enables scalable active photonic integrated circuits for visible wavelengths, and the piezoelectric actuation functions without performance degradation down to cryogenic temperatures. As an example of the potential of the platform, we demonstrate a compact (∼40 µm diameter) silicon nitride ring resonator modulator operating at 780 nm with intrinsic quality factors in excess of 1.5 million, >10 dB change in extinction ratio with 2 V applied, a switching time less than 4 ns, and a switching energy of 0.5 pJ/bit. We characterize the exemplary device at room temperature and 7 K. At 7 K, the device obtains a resistance of approximately 20 teraohms, allowing it to operate with sub-picowatt electrical power dissipation. We further demonstrate a Mach-Zehnder modulator constructed in the same platform with piezoelectrically tunable phase shifting arms, with 750 ns switching time constant and 20 nW steady-state power dissipation at room temperature.

CMOS-compatible, piezo-optomechanically tunable photonics for visible wavelengths and cryogenic temperatures

Abstract: We demonstrate a platform for phase and amplitude modulation in silicon nitride photonic integrated circuits via piezo-optomechanical coupling using tightly mechanically coupled aluminum nitride actuators. The platform, fabricated in a CMOS foundry, enables scalable active photonic integrated circuits for visible wavelengths, and the piezoelectric actuation functions without performance degradation down to cryogenic temperatures. As an example of the potential of the platform, we demonstrate a compact (~40 {\mu}m diameter) silicon nitride ring resonator modulator operating at 780 nm with intrinsic quality factors in excess of 1.5 million, >10 dB change in extinction ratio with 2 V applied, a switching time less than 4 ns, and a switching energy of 0.5 pJ/bit. We characterize the exemplary device at room temperature and 7 K. At 7 K, the device obtains a resistance of approximately 20 Teraohms, allowing it to operate with sub-picowatt electrical power dissipation. We further demonstrate a Mach-Zehnder modulator constructed in the same platform with piezoelectrically tunable phase shifting arms, with 750 ns switching time constant and 20 nW steady-state power dissipation at room temperature.

Design of a novel structure capacitive RF MEMS switch to improve performance parameters

Abstract: This study reports the design and analysis of novel step structure RF micro-electromechanical system (MEMS) switch for low pull-in voltage, low insertion loss and high isolation by using uniform single meander. The central beam of the membrane is designed with 0.5 µm lower than the side beams to form a step-down structure which reduces the pull-in voltage. Stress analysis, electromechancial, switching time, quality factor and RF analysis have done to understand the behavioural characteristics of the proposed step-down switch. The analysis has been carried out for different beam and dielectric materials among them switch with gold material exhibits low pull-in voltage of 4.7 V, low insertion loss <1 dB and high isolation of −38.3 dB at 28.2 GHz for silicon nitride. The switch also shows good quality factor of 0.95 for gold material along with high capacitance ratio of 132. The upstate capacitance of 56.8 pF contributes low return loss and made the switch to transmit the signal up to 26.2 GHz and provides 7.2 pF of downstate capacitance to produce high isolation at 26.2 GHz which is efficiently used for K-band satellite applications.

Materials Impact on the Performance Analysis and Optimization of RF MEMS Switch for 5G Reconfigurable Antenna

Abstract: In this paper, we have enhanced the performance of the existing switch operating at 35 GHz by using a novel optimization process and these results are compared with the existing experimental results. The same optimization process is utilized to design the switch at 5G mobile communication frequencies (38 GHz) and its performance is analyzed. The switch is designed on the coplanar waveguide having 50 Ω impedance matching and is optimized based on the wireless application system for Ka-band (27–40 GHz) at a resonance frequency of 38 GHz. The proposed switch at 38 GHz exhibits low input reflection coefficient (S11) of 13.86 dB (> 10 dB), low insertion loss (S12) of 0.44 dB (< 1 dB) and high isolation (S21) of 33 dB at Ka-band frequencies. The proposed structure is designed to have less spring constant of 2.38 N/m and actuation voltage of 11.97 V. During UP state position switch develops an ON-state capacitance of 31 fF and OFF state capacitance of 0.152 pF during downstate with a capacitance ratio of 4.90. The switch requires low switching time of 0.19 ms and it can withstand up to the force of 12.97 × 10−4 N which is generated during actuation. Thus, the proposed switch can be effectively optimized for good performance and can be used for high-frequency 5G communication applications.

Compact thermo-optic MZI switch in silicon-on-insulator using direct carrier injection.

Abstract: In this paper we present a compact direct current injection thermo-optic switch based on a Mach-Zehnder Interferometer configuration that is suitable for autonomous vehicle applications as it has a low heating resistance value of 97 Ω, a rapid 2.16 μs switching time constant, and a Pπ of 28 mW. The device relies on multimode interference to achieve low optical insertion losses of less than 1.1 dB per device, while allowing direct current injection to heat the waveguide and achieve fast operation speeds. Furthermore, the total resistive value can be tailored as the heating elements are placed in parallel.

Reconfigurable and Scalable Multimode Silicon Photonics Switch for Energy-Efficient Mode-Division-Multiplexing Systems

Abstract: A novel integrated scalable multimode switch (SMS) is experimentally demonstrated using tapered multimode-interference-based couplers and Ti/W metal heater phase shifters for mode-division-multiplexing (MDM) silicon photonics switching. The SMS allows path-reconfigurable switching of the first two (TE0 and TE1) or the first three (TE0, TE1, and TE2) transverse electric (TE) modes using the same device achieving footprint efficiency for higher bandwidth density. A proof-of-concept realization of the two-mode switch demonstrates the (de)multiplexing and switching of broadband optical signals over the TE0 and TE1 modes exhibiting $-$ 6.5 dB insertion loss (IL) in the bar state and $-$ 7.3 dB IL in the cross state at 1550 nm with less than $-$ 14 dB crosstalk. Simultaneous switching of two parallel TE modes (TE0+TE1) exhibits less than $-$ 7.0 dB IL and $-$ 11.9 dB crosstalk at 1550 nm. An aggregated bandwidth of 2 × 10 Gb/s is experimentally achieved while switching between two non-return-to-zero PRBS31 data signals with <9.8 $\mu$ s switching time and >17.7 dB switching extinction ratio (ER) for individual-mode transmission, and <7.6 $\mu$ s switching time and >12.0 dB switching ER for dual-mode transmission. The SMS is scalable to switch higher order TE modes with lower energy consumption (up to 63% less) than the single-mode switches indicating its potential application in energy-efficient MDM photonic networks.

High Frequency Conducted EMI Investigation on Packaging and Modulation for a SiC-Based High Frequency Converter

Abstract: Silicon carbide (SiC) devices have the advantages of high switching speed and high switching frequency, which can increase the power density, but electromagnetic interference (EMI) will increase along with higher switching frequency thus it can become a challenge for high-frequency converters. In order to clarify the influence factors of EMI noise in SiC converters and find the suppressing method, this paper investigated the conducted EMI in SiC-based high power density electronic systems from two aspects: packaging structures and modulation methods. For packaging investigation, this paper introduced parasitic parameters of power module into EMI analytical model, then defined transfer functions of EMI noise to analyze the influence of parasitic parameters on noise propagation path and further studied the impact of parasitic parameters on noise source by analyzing switching transient and frequency spectrum. Analysis and simulation are carried out based on a hybrid structure SiC power module and discrete SiC devices to verify the analysis. The influence of modulation on EMI is studied by analyzing and comparing two modulations: continuous current modulation (CCM) and triangle current modulation (TCM). To certify the analysis study, two 1.6-kW, 300-kHz switching-frequency synchronous buck converters are designed and tested. One is based on the hybrid packaging power module and the other is based on TO-247 packaged SiC devices, respectively. The result shows that the hybrid packaging module can suppress the common mode (CM) EMI by 10 dB, and has a suppression on differential mode (DM) EMI between 10 and 20 MHz. Moreover, TCM can increase DM EMI in low-frequency range but suppress it in the high-frequency range.