Design Of Diodes Research Articles

Design of a large-radius high impedance intense current diode based on gradient magnetic field

In order to reduce the size of high impedance diodes and magnetic energy consumptions, a high impedance intense current diode is designed in this paper. By reducing the center radius of the cathode and utilizing the gradient magnetic field, the electron beam is emitted in the cathode with a small radius and transmitted in the drift tube with a large radius. The influence of magnetic field distribution on the electron beam transmission is analyzed by particle-in-cell simulation. When the diode voltage is 680 kV, the impedance is 77 Ω, and the cathode radius is 60 mm, the anode radius of the traditional diode is 116 mm and the cathode–anode axial gap is 57 mm. At the same voltage and impedance, the cathode radius of the novel diode is 38 mm, the anode radius is reduced to 80 mm, and the cathode–anode axial gap is shortened to 36 mm. Further application of the novel diode to a relativistic triaxial klystron amplifier device shows that the output power of the novel diode is the same as that of the traditional diode. Through simple quantitative analysis, it is found that the magnetic energy consumption of the novel diode is less than that of the traditional diode. To sum up, the novel diode can achieve good performances in a smaller volume than the traditional diodes.

Highly efficient yellow organic light-emitting diodes with slow efficiency roll-off by mixing red and green emissions

In this work, we report the design and optimization of yellow organic light-emitting diodes (OLEDs) with tris [2-(p-tolyl)pyridine]iridium (III) (Ir (mppy)3) doped 4,4′,4′-tris(N-carbazolyl)triphenylamine (TCTA) and bis(2-phenylquinoline) (2,2,6,6-tetramethylheptane-3,5-dionate)iridium (III) (PQ2Ir (dpm)) doped 2,6-bis(3-(9H-carbazol-9-yl)phenyl)phyridine (26DCzPPy) films as green and red light-emitting layers (EMLs). Experimental results demonstrated that the designed double EMLs system is beneficial in carriers' distribution, exciton confinement and reducing triplet exciton quenching because of the matched energy levels and triplet energies of hosts and dopants. Finally, the optimal device showed a very maximal current efficiency of 65.51 cd/A, slow roll-off of efficiency with a very high current efficiency of 63.54 cd/A at 5000 cd/m2, and excellent yellow emission with CIE coordinates of (0.468, 0.493) at 10 mA/cm2.

Electromagnetic diode action in an asymmetric side-coupled cavity-resonator system

A novel compact electromagnetic diode based on Fano resonance is reported, realized by combining a ­defective photonic crystal with a varactor-loaded split ring resonator. One-way response is achieved in a microwave waveguide system, attributed to the sharp asymmetric Fano lineshape, the strong nonlinearity enhancement, and the pronounced nonreciprocal field localization. A low threshold intensity of −1.6 dBm, a high transmission contrast up to 17.1 dB, and a maximal transmission over −16 dB are achieved within a subwavelength volume. Compared with conventional electromagnetic diode designs based on ­defective photonic crystals, the presence of interaction between cavity and resonator provides more flexibility in tuning the transmission properties. The findings may be beneficial for designing nonreciprocal integrated photonic devices in practical application.

Influence of Natural Convection on Design of Thermal Diodes

Thermal diode, analogous to the electrical diode, is an emerging field of interest due to its potential application in thermal management, thermal shielding, and thermal circuits. Application of Phase Change Material (PCM) is among the different approaches proposed and analyzed to achieve high thermal rectification. However, these studies often limit the analysis to conduction heat transfer and neglect advection. In the present study, the influence of natural convection on conventional single PCM-based thermal diodes' thermal rectification has been analyzed. Natural convection enhances heat transfer in the inverse direction of gravity, augmenting thermal rectification of diodes with preferential flow in the opposite direction of gravity, whereas adversely affecting the performance of thermal diodes with preferential heat flow in the direction of gravity. Therefore, the design of thermal diode with preferential flow in gravity direction is modified to limit natural convection via the use of metal foam and baffles. The non-phase change material in a thermal diode with preferential flow in the direction inverse to the gravity is replaced with phase change material augmenting the natural convection because of the increase in length. The modified designs led to a mean thermal rectification enhancement of approximately 85% and 1275% in thermal diodes with preferential towards gravity and inverse to the gravity directions, respectively. A thermal rectification of more than 50 is achieved in a modified thermal rectifier for preferential flow in the direction inverse to the gravity.

Integrated nanophotonic optical diodes designed by genetic algorithms.

Integrable nanophotodiode devices have attracted much research interest in recent years because of their potential applications in all-optical computing and optical communication systems. We propose a new optical diode design scheme. We use genetic algorithms (GAs) to design an optical diode, which has a device footprint of only 2.5×2.5µm2. These devices designed by GA have the ability to achieve high-efficiency unidirectional transmission. Simulations show the forward transmission efficiency can reach higher than 65% for a Gaussian beam between the wavelengths of 1400 and 1600 nm, and the peak transmission efficiency reaches 75%. The transmission contrast at the design wavelength between 1500 and 1600 nm is higher than 90%, which meets the requirements of high unidirectionality, wide operational bandwidth, and small scale. The devices have more advantages for optical diodes compared with structures designed by photonic crystals and gratings. The application of this scheme provides a new idea for the design and research of all-optical diodes in the field of optical communication.

Design of New Over-Temperature Protection Light-Emitting Diode Driver Circuit and Improvement Method of Visual Design

The overall design of light-emitting diode (LED) display control system was completed at first. For the problems of LED driver chip such as low accuracy of constant current output, high power consumption, poor stability, and single over-temperature protection function, the double temperature hysteresis and over-temperature buffer protection function of circuit were designed. The low-power constant-current module of LED driver module included an operational amplifier, a MOS tube with negative feedback control, and the driving current required to achieve high-precision reference current conversion. The temperature control points were set in hysteretic and overtemperature buffer modules for the working temperature, and power MOS tube was turned off in time to reduce the driving current to a constant driving current, thus reducing the power consumption of circuit. In addition, to improve the image quality of LED display, a visual refresh logic circuit was designed. The display cycle was divided into 32 segments by logic circuit, with 128 gray clock cycles in each segment, and duty ratio was controlled by 12 bits of gray data. In test, the multi-value output bandgap reference voltage was simulated at first. In range of –30 °C–130 °C, the fluctuation of voltage in this temperature range met the requirements of circuit. During simulation of buffer circuit of the LED driver module, it was found that output terminal can perform good voltage following, so as to meet the needs of circuit. The design of visual refresh logic circuit can greatly improve the refresh rate of pulse width modulation (PWM).

Study of p-SiC/n-GaN Hetero-Structural Double-Drift Region IMPATT Diode.

Nowadays, the immature p-GaN processes cannot meet the manufacturing requirements of GaN impact ionization avalanche transit time (IMPATT) diodes. Against this backdrop, the performance of wide-bandgap p-SiC/n-GaN heterojunction double-drift region (DDR) IMPATT diode is investigated in this paper for the first time. The direct-current (DC) steady-state, small-signal and large-signal characteristics are numerically simulated. The results show that compared with the conventional GaN single-drift region (SDR) IMPATT diode, the performance of the p-SiC/n-GaN DDR IMPATT proposed in this design, such as breakdown voltage, negative conductance, voltage modulation factor, radio frequency (RF) power and DC-RF conversion efficiency have been significantly improved. At the same time, the structure proposed in this design has a larger frequency bandwidth. Due to its greater potential in the RF power density, which is 1.97 MW/cm2 in this study, indicates that the p-SiC/n-GaN heterojunction provides new possibilities for the design and manufacture of IMPATT diode.

Analysis of Electrical and Thermal Models for Pulsed IMPATT Diode Simulation

Some nonlinear models are presented for modeling and analyzing IMPATT high-power pulse diodes. These models are suitable for analyzing different operating modes of the oscillator. The first model is a precise one, which describes all important electrical phenomena on the basis of the continuity equations and Poisson´s equation, and it is correct until 300 GHz. The second approximate mathematical model suitable for the analysis of IMPATT diode stationary operation oscillator and for optimization of internal structure of the diode. The temperature distribution in the semiconductor structure is obtained using the special thermal model of the IMPATT diode, which is based on the numerical solution of the non-linear thermal conductivity equation. The described models can be applied for the analysis, optimization and practical design of pulsedmode millimetric IMPATT diodes. It can also be used to evaluate the thermal behavior of diodes, to correctly select the shape and amplitude of a supply pulse, and to design various types of high-power pulsed millimeter IMPATT diodes with a complex doping profile with improved characteristics.

Understanding Carbon Nanotube‐Based Ionic Diodes: Design and Mechanism

The rectification of ion transport through biological ion channels has attracted much attention and inspired the thriving invention and applications of ionic diodes. However, the development of high-performance ionic diodes is still challenging, and the working mechanisms of ionic diodes constructed by 1D ionic nanochannels have not been fully understood. This work reports the systematic investigation of the design and mechanism of a new type of ionic diode constructed from horizontally aligned multi-walled carbon nanotubes (MWCNTs) with oppositely charged polyelectrolytes decorated at their two entrances. The major design and working parameters of the MWCNT-based ionic diode, including the ion channel size, the driven voltage, the properties of working fluids, and the quantity and length of charge modification, are extensively investigated through numerical simulations and/or experiments. An optimized ionic current rectification (ICR) ratio of 1481.5 is experimentally achieved on the MWCNT-based ionic diode. These results promise potential applications of the MWCNT-based ionic diode in biosensing and biocomputing. As a proof-of-concept, DNA detection and HIV-1 diagnosis is demonstrated on the ionic diode. This work provides a comprehensive understanding of the working principle of the MWCNT-based ionic diodes and will allow rational device design and optimization.

Bipolar Nanochannels: A Systematic Approach to Asymmetric Problems.

Nanofluidic diodes are capable of rectifying the electrical current by several orders of magnitude. In the current state of affairs, determining the rectification factor is not possible as it depends on many system parameters. In this work, we systematically scan the effects of geometry and excess counterion concentrations (i.e., surface charge effects). We show that the current-voltage response varies between the two extreme behaviors of unipolar and bipolar responses. The exact behavior depends on the geometry and surface charge properties of the system. Here, we have gone beyond the typical setup that only considers the dynamics within the nanochannel itself and we have included the effects of the adjoining microchannels. Systems that include both nanochannels and microchannels exhibit the classical signatures of concentration polarization, such as ionic depletion and enrichment. Here, where we have scanned a wide range of parameters, we show that bipolar and semi-bipolar systems exhibit a wider range of phenomena that are intrinsically more complicated. Our system characterization is for both, the much more investigated case of steady state and the less investigated, but equally interesting, time-transient case. For example, it is common to characterize the system by its steady-state result (current-voltage response, rectification factor, and transport number). Here, we demonstrate that the time-transient behavior of the fluxes can also be used to characterize the system, and that the time-dependent rectification factors and transport numbers are meaningful. The systematic approach taken in this work, and the results presented herein, can be used to further elucidate the complicated behavior of the current-voltage response of nanofluidic diodes and to rationalize experimental results. The insights of this work can be used to enhance and improve the design of all nanofluidic diodes.

Design and Characterization of Backside Termination Structures for Thick Fully-Depleted MAPS.

Fully Depleted Monolithic Active Pixel Sensors (FD-MAPS) represent an appealing alternative to hybrid detectors for radiation imaging applications. We have recently demonstrated the feasibility of FD-MAPS based on a commercial 110 nm CMOS technology, adapted using high-resistivity substrates and backside post-processing. A p/n junction diode, fabricated on the detector backside using low-temperature processing steps after the completion of the front-side Back End of Line (BEOL), is reverse-biased to achieve the full depletion of the substrate and thus fast charge collection by drift. Test diodes including termination structures with different numbers of floating guard rings and different pitches were fabricated together with other Process Control Monitor structures. In this paper, we present the design of the backside diodes, together with results from the electrical characterization of the test devices, aiming to improve understanding of the strengths and limitations of the proposed approach. Characterization results obtained on several wafers demonstrate the effectiveness of the termination rings in increasing the breakdown voltage of the backside diodes and in coping with the variability of the passivation layer characteristics. A breakdown voltage exceeding 400 V in the worst case was demonstrated in devices with 30 guard rings with 6 μm pitch, thus enabling the full depletion of high-resistivity substrates with a thickness larger than or equal to 300 μm. Additionally, we show the first direct comparison for this technology of measured pixel characteristics with 3D TCAD simulations, proving a good agreement in the extracted operating voltages.

(Invited) In silico Material Design and Realization of Highly-Efficient Organic Light-Emitting Diodes

Conversion of triplet excitons into light is very important to realize highly efficient organic light-emitting diodes (OLEDs). One solution is the use of transition-metal-based phosphorescent materials.1,2 Thermally activated delayed fluorescence (TADF)3 is another solution. Recently, we have developed various type of excellent TADF emitters using a simple high-throughput screening method. In this talk, I will present the method and the results we have obtained.4-8 The OLED performances are excellent, but further improvements are necessary to overcome efficiency roll-off problem etc. I will also show our recently proposed material design concept,9 named tilted Face-to-Face alignment with Optimal distance (tFFO), to further accelerate reverse intersystem crossing (RISC). Using this design concept, we developed a new material, TpAT-tFFO (Figure), which provided very fast RISC with a rate constant (k RISC) over 107 s-1.The results of multiscale charge transport simulations10-13 and dynamic nuclear polarization enhanced solid-state NMR14 will be also presented, if time permits.We express sincere thanks to my group members, Prof. Adachi, and his group members. This work was supported by JSPS KAKENHI Grant Numbers JP20H05840 (Grant-in-Aid for Transformative Research Areas, “Dynamic Exciton”), JP17H01231, and JP17J09631, and FIRST Program. Computation time was provided by the Super Computer System, Institute for Chemical Research, Kyoto University. NMR measurements were supported by the international Joint Usage/Research Centre (iJURC) at the Institute for Chemical Research, Kyoto University, Japan. M. A. Baldo et al. Appl. Phys. Lett. 75, 4 (1999).H. Sasabe and J. Kido, Eur. J. Org. Chem. 2013, 7653 (2013).H. Uoyama et al. Nature, 492, 234 (2012).H. Kaji et al. Nat. Commun., 6, 8476 (2015).K. Suzuki et al. Angew. Chem. Int. Ed., 54, 15231 (2015).T. Miwa et al. Sci. Rep., 7, 284 (2017).Y. Wada et al. Appl. Phys. Lett., 107, 183303 (2015).Y. Wada et al. Adv. Mater. 30, 1705641 (2018).Y. Wada, H. Nakagawa, S. Matsumoto, Y. Wakisaka, and H. Kaji, ChemRxiv, https://doi.org/10.26434/chemrxiv.9745289.v1 (2019); Nat. Photon. 14, 643 (2020).F. Suzuki et al. J. Mater. Chem. C 3, 5549 (2015).H. Uratani et al. Sci. Rep. 6, 39128 (2016).F. Suzuki et al. Sci. Rep. 8, 5203 (2018).S. Kubo et al. Sci. Rep. 8, 13462 (2018).K. Suzuki et al. Angew. Chem. Int. Ed. 56, 14842 (2017). Figure 1

Design of PAMBE-based selective-area growth compliant ultra-low leakage GaN mixed-conduction vertical diodes for high-power applications * *This work was supported by the Office of Naval Research (ONR) under the ONR Award N00014-17-1-2681 (Program Manager: Lynn J Petersen).

Modern high-speed power applications require diodes with high-current capacity, larger reverse blocking voltage, lower reverse recovery transients, and lower leakage. GaN mixed-conduction vertical diodes are an attractive option for these operations. Experimentally reported GaN diodes have two major shortcomings, namely, higher leakage due to non-optimum design and conventional processing methods (e.g. ion implantation and dry etching), introducing huge leakage components. In this work, we design ultra-low leakage GaN buried p-base merged p–i–n Schottky and buried p-base merged p–i–n junction barrier controlled Schottky diodes, capable of reducing leakage current by more than five orders of magnitude by virtue of strong reduced surface field effect. Moreover, these designs are fully compliant with our earlier reported silicon nitride shadowed selective-area growth (SNS-SAG) methodology, capable of reducing the leakage by at least four orders of magnitude. In combination with SNS-SAG and highly efficient dielectric vertical sidewall edge termination scheme, these designs provide attractive options for higher performance.

Topology optimization of fluid flow by using Integer Linear Programming

Topology optimization of fluid flow problems is still a challenging open problem, especially when considering turbulence, compressibility, or the addition of different physics. In the current implementation of topology optimization for fluids considering density methods, there are essentially three problems. First, the grayscale in the result makes it difficult to identify the precise contour of the fluid region, which may be a problem in some applications and during the optimization process as well. Second, even for low Reynolds flow design problems, a continuation scheme of the material model penalization parameters is necessary to avoid a grayscale and to obtain a clear boundary. Third, in complex fluid flow optimization problems, it is difficult to specify the maximum value of the inverse permeability to avoid the fluid to flow inside the solid. This work proposes a novel methodology that tackles the first two problems, i.e., it avoids the grayscale and obtains clear boundaries. The goal of this work is to implement the Topology Optimization of Binary Structures (TOBS) (Sivapuram and Picelli, Finite Elem Anal Des 139:49–61, 2018) for fluid flow design, which is a novel topology optimization method that has been used in solid mechanics to generate optimized structural solutions considering only binary {0,1} design variables. The main advantage of {0,1} methods is the clear definition of the interface and the absence of grayscale. It is a method easy to implement which preserves the material distribution features. Some classic fluid problems are considered to illustrate the problem, such as the double channel and the bend pipe, and also a more complex example that usually presents grayscale issues, which is the fluid diode design. The optimization results show the feasibility of the TOBS when applied to fluid flow problems. The physical problem is solved by using the finite element method and the optimization problem with CPLEXⒸ, a proprietary optimization package from IBM. The present work successfully eliminates the grayscale problem, bringing clear boundaries in the interface fluid-solid.

Combustion synthesis of Ba3Y1-xSm3+ x(BO3)3 asred-light emitting phosphors for indoor plant cultivation applications

In this paper, a series of Sm activated Ba3Y(BO3)3 phosphors are synthesized byhigh-temperature solution combustion method. The concentration of Sm ions is changed from 1 to 5 mol% in the host lattice of BYB crystal. The crystal structure, phase of formation, particle size, elemental analysis, photoluminescence study of synthesized phosphors aredone using X-ray diffraction, FE-SEM, Fourier transform infrared spectroscopy (FTIR) and photo luminescent (PL) techniques. The excitation spectra consisted of strong bands in the NUV and blue region. The phosphors on excitation at 449 nm exhibited a strong emission peak in the region 630-660 nm, which corresponds to the absorption spectra of PR phytochrome. The obtained photometric results show that these can be used for the design of light-emitting diodes for indoor plant applications, houseplants gardening and in horticultural fixtures.

High Stability of Liquid-Typed White Light-Emitting Diode with Zn0.8Cd0.2S White Quantum Dots

In this study, we demonstrate a new design of white light-emitting diode (WLED) with high stability and luminous efficiency as well as positive aging. Colloidal ternary Zn0.8Cd0.2S (named Zn0.8) white quantum dots (WQDs) were prepared by chemical route and dispersed in xylene, integrating them into an ultraviolet light-emitting diode (UV-LED) to form WQD-white light emitting diode (WQD-WLED). High efficiency, high color quality and excellent reliability of WQD-WLED with neutral white correlated color temperature (CCT) can be obtained. The experimental results indicate that the stability of relative luminous efficiency and color rendering index (CRI) of the WQD-WLED can reach up to 160 and 82%, respectively. Moreover, the WQD-WLED can operate more than 1000 h under 100 mA, and the quantity of WQDs in the glass package can be reduced.

Tesla's fluidic diode and the electronic-hydraulic analogy

Reasoning by analogy is powerful in physics for students and researchers alike, a case in point being electronics and hydraulics as analogous studies of electric currents and fluid flows. Around 100 years ago, Nikola Tesla proposed a flow control device intended to operate similarly to an electronic diode, allowing fluid to pass easily in one direction but providing high resistance in reverse. Here, we use experimental tests of Tesla's diode to illustrate principles of the electronic-hydraulic analogy. We design and construct a differential pressure chamber (akin to a battery) that is used to measure flow rate (current) and thus resistance of a given pipe or channel (circuit element). Our results prove the validity of Tesla's device, whose anisotropic resistance derives from its asymmetric internal geometry interacting with high-inertia flows, as quantified by the Reynolds number (here, Re∼103). Through the design and testing of new fluidic diodes, we explore the limitations of the analogy and the challenges of shape optimization in fluid mechanics. We also provide materials that may be incorporated into lesson plans for fluid dynamics courses, laboratory modules, and further research projects.

Design, Fabrication, and Verification of Blue-Extended Single-Photon Avalanche Diode with Low Dark Count Rate and High Photon Detection Efficiency

Single-photon avalanche diodes (SPADs) can detect extremely weak optical signals and are mostly used in single-photon imaging, quantum communication, medical detection, and other fields. In this paper, a low dark count rate (DCR) single-photon avalanche diode device is designed based on the 180 nm standard BCD process. The device has a good response in the 450~750 nm spectral range. The active area of the device adopts a P+/N-Well structure with a diameter of 20 µm. The low-doped N-Well increases the thickness of the depletion region and can effectively improve the detection sensitivity; the P-Well acts as a guard ring to prevent premature breakdown of the PN junction edge; the isolation effect of the deep N-Well reduces the noise coupling of the substrate. Use the TCAD simulation tool to verify the SPAD’s basic principles. The experimental test results show that the avalanche breakdown voltage of the device is 11.7 V. The dark count rate is only 123 Hz when the over-bias voltage is 1 V, and the peak photon detection efficiency (PDE) reaches 37.5% at the wavelength of 500 nm under the 0.5 V over-bias voltage. PDE exceeds 30% in the range of 460~640 nm spectral range, which has a good response in the blue band. The SPAD device provides certain design ideas for the research of fluorescence detectors.

AlGaAs/GaAs asymmetric‐waveguide, short cavity laser diode design with a bulk active layer near the p ‐cladding for high pulsed power emission

It is shown theoretically that a GaAs/AlGaAs laser diode design using an asymmetric waveguide structure and a bulk active layer (AL), located close to the p-cladding, can provide high output power in a single, broad transverse mode for short-wavelength (<0.9 μm, matching the spectral range of high efficiency of silicon photodetectors) pulsed emission in the nanosecond pulse duration region, typically <<100 ns. The dependences of the laser performance on the thickness of the AL and the cavity length are analysed. It is shown that the relatively thick bulk AL allows the of short cavity lengths (<1 mm), for achieving high pulsed power while maintaining a relatively low series resistance and a narrow far field.

A surface charge governed nanofluidic diode based on a single polydimethylsiloxane (PDMS) nanochannel

HypothesisNanofluidic diodes have attracted intense attention recently. Commonly used materials to design these devices are membrane-based short nanopores and aligned Carbon nanotube bundles. It is highly desirable and very challenging to develop a nanofluidic diode based on a single PDMS nanochannel which is easier to be introduced into an integrated electronic system on a chip. Layer-by-layer (LBL) deposition of charged polyelectrolytes can change the size and surface properties of PDMS nanochannels that provides new possibilities to develop high-performance nanofluidic based on PDMS nanochannels. ExperimentsA novel design of nanofluidic diode is presented by controlling the surface charges and sizes of single PDMS nanochannels by surface modification using polyelectrolytes. Polybrene (PB) and Dextran sulfate (DS) are used to reduce the PDMS nanochannel size to meet the requirement of ion gating by LBL method and generate opposite surface charges at the ends of nanochannels. The parameters of such a nanofluidic diode are investigated systematically. FindingsThis nanofluidic diode developed in this work has high effective current rectification performance. The rectification ratio can be as high as 218 which is the best ever reported in PB/DS modified nanochannels. This rectification ratio reduces with high voltage frequency and ionic concentration whereas increases in shorter nanochannels.