Diode Research Articles

Performance improvements of power converters for high power induction motor drive

This paper deals with a reliable transformer configuration with simple wiring and less number windings for twenty-four pulse AC-DC converter, which is used in medium voltage drive system so that it can adverse the effects produced by harmonics currents fed into the grid by converters that do not affect other consumers connected to the same electrical grid. Apart from this, a five-level symmetrical multilevel inverter configuration is used by cascading four two-level voltage source inverters. It is designed with less quantity of components counts like; power switches, diodes and electrolytic capacitors. Because power quality impacts the suitability of electrical power for consumer electronics, an attempt is made in this work to improve power quality through the connecting high-pulse converter at the grid end instead of 12-pulse and modified level-shifted pulse width modulation for a multi-level inverter at the drive end. Performance of the described topology is verified in the laboratory using a drive-through MATLAB/Simulink environment and a prototype at a reduced scale. The feasibility and effectiveness of the proposed topology are demonstrated by a comprehensive comparison with recently reported schemes. Promising results validate this new concept.

General Design Concepts for CAPodes as Ionologic Devices

AbstractCapacitive analogues of semiconductor diodes (CAPodes) present a new avenue for energy‐efficient and nature‐inspired next‐generation computing devices. Here, we disclose the generalized concept for bias‐direction‐adjustable n‐ and p‐CAPodes based on selective ion sieving. Controllable‐unidirectional ion flux is realized by blocking electrolyte ions from entering sub‐nanometer pores. The resulting CAPodes exhibit charge‐storage characteristics with a high rectification ratio (96.29 %). The enhancement of capacitance is attributed to the high surface area and porosity of an omnisorbing carbon as counter electrode. Furthermore, we demonstrate the use of an integrated device in a logic gate circuit architecture to implement logic operations (‘OR’, ‘AND’). This work demonstrates CAPodes as a generalized concept to achieve p‐n and n‐p analogue junctions based on selective ion electrosorption, provides a comprehensive understanding and highlights applications of ion‐based diodes in ionologic architectures.

General Design Concepts for CAPodes as Ionologic Devices.

Capacitive analogues of semiconductor diodes (CAPodes) present a new avenue for energy-efficient and nature-inspired next-generation computing devices. Here, we disclose the generalized concept for bias-direction-adjustable n- and p-CAPodes based on selective ion sieving. Controllable-unidirectional ion flux is realized by blocking electrolyte ions from entering sub-nanometer pores. The resulting CAPodes exhibit charge-storage characteristics with a high rectification ratio (96.29 %). The enhancement of capacitance is attributed to the high surface area and porosity of an omnisorbing carbon as counter electrode. Furthermore, we demonstrate the use of an integrated device in a logic gate circuit architecture to implement logic operations ('OR', 'AND'). This work demonstrates CAPodes as a generalized concept to achieve p-n and n-p analogue junctions based on selective ion electrosorption, provides a comprehensive understanding and highlights applications of ion-based diodes in ionologic architectures.

BASIC PRINCIPLES OF CONSTRUCTION OF MODULAR HARDWARE COMPLEXES FOR LED THERAPY

The industrial production of powerful light-emitting diodes has led to the appearance of devices for therapeutic purposes, where such diodes are used as sources of electromagnetic radiation in the optical range. The development and production of such devices was established in the city of Kharkiv with the participation of scientists and specialists of Kharkiv National University named after V.M. Karazin and National Technical University "Kharkiv Polytechnic Institute". Methods of using devices and hardware complexes in medical practice were created at the Kharkiv Medical Academy of Postgraduate Education. The article analyzes the main principles of building modular hardware complexes for LED therapy, defines structures and options for connecting modules. As a result of the work performed, it was established that the modular implementation of hardware complexes for LED therapy has five main options, which differ in the number and types of emitters connected to the control unit, in the connection scheme of photon emitters, and in their functionality. It was also noted that the modular principle of building hardware complexes for LED therapy makes it quite easy to carry out their modernization and form the necessary configuration of the irradiating system, that is, to significantly expand the functional capabilities of the complex for carrying out phototherapy treatment procedures with the greatest efficiency. The expediency of using microprocessor technology for the implementation of the information part of the control unit of the complex is shown. This makes it possible to ensure the operation of photon emitters in continuous, pulsed and scanning modes, as well as separate operation of the emitters of the irradiation system of the complex and irradiation of the patient in biosynchronization mode.

Theoretical analysis of time delay echoes in multimode semiconductor diode laser with optical feedback

Theoretical analysis of time delay echoes in multimode semiconductor diode laser with optical feedback

A self-aligned Ga2O3 heterojunction barrier Schottky power diode

We report an alignment-free gallium oxide (Ga2O3) heterojunction barrier Schottky (HJBS) power diode, which utilizes the self-assembled Ni nanostructures as in situ masks for the trench etching of Ga2O3 and the subsequent selective-area filling of p-type NiO. By increasing the trench depth to 200 nm, the relevant HJBS diode exhibits improved reverse blocking capabilities including the reduced leakage current density of 10−8 A/cm2 (at a reverse bias of 100 V) and the enhanced breakdown voltage of 748 V, while maintaining the forward biasing characteristics similar to the Schottky barrier diode (SBD). The variation of turn-on voltage and the reverse breakdown features indicate the conversion of the HJBS diodes characteristics from Ni/Ga2O3 SBD to the NiO/Ga2O3 p-n heterojunction diode. The electrical field simulations and experimental facts imply that the remarkable lateral pinch-off effect in the 200-nm trenched diodes shields the electric field in the depletion region underneath the Ni/Ga2O3 Schottky contact. This work provides a straightforward strategy to simplify the fabrication process of Ga2O3-based HJBS diodes with both promising forward and reverse performances.

Vertical metal–dielectric–semiconductor diode on (001) β-Ga2O3 with high-κ TiO2 interlayer exhibiting reduced turn-on voltage and leakage current and improved breakdown

We demonstrate vertical Pt/TiO2/β-Ga2O3 metal–dielectric–semiconductor (MDS) diodes and compare performance with co-fabricated Pt/β-Ga2O3 Schottky diodes (SBDs). The MDS diode exhibits a lower turn-on voltage and leakage current. In addition, the breakdown voltage increased from 548 V for an SBD to 1380 V for a MDS diode. The improvement in the off-state characteristics compared to a SBD while simultaneously reducing on-state losses leads to lower power dissipation at all duty cycles, indicating the great promise of this device architecture for advancing low-loss β-Ga2O3 rectifiers toward material limits.

1 kV GaN-on-Si Quasi-Vertical Schottky Rectifier

This work demonstrates quasi-vertical GaN Schottky barrier diodes (SBDs) on 6-inch Si substrate with a breakdown voltage (BV) over 1 kV, the highest BV reported in vertical GaN-on-Si SBDs to date. The deep mesa inherently in quasi-vertical devices is leveraged to form a self-aligned edge termination, and the mesa sidewall is covered by the p-type nickel oxide (NiO) as a reduced surface field (RESURF) structure. This novel termination enables a parallel-plate junction electric field of 2.8 MV/cm, being close to the material limit for GaN. The device also shows a high on/off ratio of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> , low turn-on voltage of 0.5 V, and low specific on-resistance of 1.1 mΩ∙cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Moreover, the device exhibits excellent overvoltage robustness under the continuous 800 V stress in the unclamped inductive switching test. These results show the good promise of the low-cost vertical GaN-on-Si power diodes.

Photo-assisted Cl-, Br- and I- production in caesium sputter ion source

We have measured the effect of 445 nm, high power diode laser, directed on the cathode of a SNICS ion source on the extracted beam currents of Cl-, Br- and I- ion beams. Beam current enhancement factors up to 9 were observed in Cs-depleted operation mode of the ion source. The photo-assisted enhancement is shown to scale with the laser power and depend strongly on the neutral Cs flux into the ion source. The effect of the laser diminishes with increasing Cs oven temperature. We present a qualitative model, supported by cathode current measurement, arguing that photoelectron emission and Cs coverage of the cathode surface could explain the observations.

Trap‐Assisted Charge Generation and Recombination in State‐of‐the‐Art Organic Photodetectors

AbstractThe performance of organic photodetectors is steadily improving, and the specific detectivity, as a key figure of merit, has reached values of 1012–1013 Jones, i.e., comparable to that of silicon diodes but still considerably lower than the intrinsic limit. As with other semiconductor devices, the electrical performance of state‐of‐the art organic photodiodes (OPDs) is presently determined to a high degree by the presence of chemical impurities or structural defects which create carrier trapping states within the bandgap of organic active layer. This review aims to provide a comprehensive and timely account of trap‐assisted charge generation and recombination in OPDs, with emphasis on the impact of these phenomena on photodetector performance parameters such as, noise and dark current density, responsivity, response speed, and ultimately, specific detectivity.

Challenges and prospects for multi-chip microlens imprints on front-side illuminated SPAD imagers.

The overall sensitivity of frontside-illuminated, silicon single-photon avalanche diode (SPAD) arrays has often suffered from fill factor limitations. The fill factor loss can however be recovered by employing microlenses, whereby the challenges specific to SPAD arrays are represented by large pixel pitch (> 10 µm), low native fill factor (as low as ∼10%), and large size (up to 10 mm). In this work we report on the implementation of refractive microlenses by means of photoresist masters, used to fabricate molds for imprints of UV curable hybrid polymers deposited on SPAD arrays. Replications were successfully carried out for the first time, to the best of our knowledge, at wafer reticle level on different designs in the same technology and on single large SPAD arrays with very thin residual layers (∼10 µm), as needed for better efficiency at higher numerical aperture (NA > 0.25). In general, concentration factors within 15-20% of the simulation results were obtained for the smaller arrays (32×32 and 512×1), achieving for example an effective fill factor of 75.6-83.2% for a 28.5 µm pixel pitch with a native fill factor of 28%. A concentration factor up to 4.2 was measured on large 512×512 arrays with a pixel pitch of 16.38 µm and a native fill factor of 10.5%, whereas improved simulation tools could give a better estimate of the actual concentration factor. Spectral measurements were also carried out, resulting in good and uniform transmission in the visible and NIR.

650V Vertical SiC MOSFETs and Diodes with Improved Terrestrial-Neutron Single-Event Burnout

Silicon carbide (SiC) power devices such as Schottky diodes and metal-oxide semiconductor field-effect transistors (MOSFETs) are susceptible to failure by terrestrial neutron single-event burnout (SEB) while in the high-voltage blocking state. In this study the effects of the drift layer design of 650V SiC vertical power diodes and MOSFETs have been studied. TCAD simulations of different device designs have been performed, and fabricated device single-event burnout (SEB) properties are compared between the devices fabricated. We find that the standard 650V devices have a low area-scaled failure-in-time (FIT/cm2) such that essentially no failures (0.01 FIT/cm2) are expected at 400V drain-source bias (VDS) operation and below. An improved design allows the SEB failure rate curve to be shifted downward in failure rate, such that at for a given VDS operation condition, the FIT/cm2 can be decreased by 10 - 100 times, depending on the VDS value. This allows operation at about 75V higher VDS value with a similar SEB failure rate, allowing these devices to be used in a wider range of applications.

A Low-Power DROIC With Extended-Counting ADC for Uncooled Infrared Silicon Diode Detectors

A low-power digital readout integrated circuit (DROIC) for silicon diode uncooled infrared focal plane arrays (IRFPAs) is presented. The DROIC adopts a 14-bit column-level extended-counting analog-to-digital converter (ADC) based on a cascade of a coarse continuous-time Σ-ADC and a fine single-slope ADC. While the weak detector signal is integrated, the coarse conversion is implemented by a feedback current-steering digital-to-analog converter (IDAC), which shortens the signal chain and reduces the bandwidth requirement for the op-amp, to reduce power consumption. Besides, the ramp signal of the fine conversion is generated locally by an additional column-level IDAC, which matches the coarse conversion IDAC to decrease the DNL. Also, a low-power non-uniformity calibration circuit is adopted to compensate the non-uniformity of the IRFPA and adjust the ADCfs input signal range. The DROIC with 1024 ×768 pixel array is fabricated in a 0.18μm CMOS process. The experimental results demonstrate the DROIC consumes 109mW. The noise is 1.7LSB and the equivalent input noise voltage of the column circuit is about 2.1μVrms. The INL and DNL are less than +6.1LSB/.4.4LSB and +0.40LSB/.0.38LSB, respectively.

Electrically active traps in 4H-silicon carbide (4H-SiC) PiN power diodes

Electrically active traps in 4H-silicon carbide (4H-SiC) PiN power diodes

Ultrafast-programmable two-dimensional p–n homojunction for high-performance photovoltaics and optoelectronics

Two-dimensional (2D) materials are considered to be promising candidates for constructing revolutionary electronic devices. However, difficulties in controlling the polarity, concentration, and spatial distribution of charge carriers in 2D materials make the construction of 2D p–n junctions rather challenging. Here, we report the successful construction of ultrafast-programmable 2D p–n homojunctions with a semi-floating-gate configuration based on a vertically stacked molybdenum disulfide (MoS2)/hexagonal boron nitride/multilayer graphene van der Waals heterostructure. By partially electrostatically doping the MoS2 channel under different control-gate voltage pulses, three types of 2D homojunctions, including p–n, n+–n, and n–n, can be constructed. The 2D p–n homojunction can be programmed at an ultrafast speed of within 160 ns and exhibits a large rectification ratio of ∼104. Based on a modified Shockley equation, an ideality factor of ∼2.05 is extracted, indicating that the recombination process dominated the transport mechanism. The MoS2 2D p–n homojunction shows a maximum electrical power conversion efficiency of up to 2.66% under a weak light power of 0.61 nW and a high photovoltage responsivity of 5.72 × 109 V W−1. These results indicate that the ultrafast-programmable 2D p–n homojunction has great potential for use in high-performance photovoltaics and optoelectronics.

Carrier density non-pinning at stripe edges and widened lateral far field due to longitudinal temperature variation in broad-area high power diode lasers

Broad area lasers operating at high power with improved beam quality are needed in many applications. In typical high-power diode lasers with asymmetric facet coating, it is observed that the carrier density fails to completely pin above threshold with significant levels of lateral carrier accumulation (LCA) at the front facet stripe edges. Systematic experimental data are presented to quantify such non-pinning and its effect on lateral far field in multiple diode lasers with varying longitudinal temperature variation (LTV) using spontaneous emission imaging. LTV is quantified and correlated with the carrier accumulation and its dependence on facet reflectivity and cavity length. Results of measurements under continuous wave (CW) and quasi-CW conditions are used to regulate the level of heating and, hence, to isolate the contribution of LTV and optical field profile. Conventional long resonator asymmetric-coated devices show a twofold increase in LCA from threshold to 10 A current at the front stripe edge, but LCA varies less than 20% for lower facet asymmetry or short resonators. Similarly, strong temperature driven far field broadening is observed for conventional long-resonator asymmetric-coated devices (3°–4° variation with temperature at 10 A), which is strongly reduced for lower facet asymmetry or short resonators (&amp;lt;1° at 10 A).

Analysis and Design of a New High Voltage Gain Interleaved DC–DC Converter with Three-Winding Coupled Inductors for Renewable Energy Systems

In this article, a new non-isolated interleaved DC–DC converter is proposed to provide a high voltage conversion ratio in renewable energy systems. The converter configuration is composed of a two-phase interleaved boost converter integrating a voltage-lift capacitor and three-winding coupled inductor-based voltage multiplier modules to achieve high step-up voltage conversion and reduce voltage stresses on the semiconductors (switches and diodes). The converter can achieve a high voltage conversion ratio when working at a proper duty ratio. The voltage stresses on the switches are significantly lower than the output voltage, which enables engineers to adopt low-voltage-rating MOSFETs with low on-state resistance. The switches can turn on under zero-current switching (ZCS) conditions because of the leakage inductor series reducing switching losses. Some diodes can naturally turn off under ZCS conditions to alleviate the reverse–recovery issue and to reduce reverse–recovery losses. The input current has small ripples due to the interleaved operation. The leakage inductor energy is recycled and voltage spikes on the switches are avoided. The proposed converter is suitable for applications in which high voltage gain, high efficiency and high power are required. The principle of operation, steady-state analysis and design considerations of the proposed converter are described in detail. In addition, a closed-loop controller is designed to reduce the effect of input voltage fluctuation and load change on the output voltage. Finally, a 1000 W laboratory prototype is built and tested. The theoretical analysis and the performance of the proposed converter were validated by the experimental results.

Phase-Field Crystal Studies on Grain Boundary Migration, Dislocation Behaviors, and Topological Transition under Tension of Square Polycrystals

In this paper, the tensile deformation behaviors of polycrystals after relaxation were studied using the phase-field-crystal (PFC) method. Here, the free energy density map characterized the 2D energy distribution of atomic configuration effectively. The application of the Read–Shockley equation distinguished high-energy grain boundary (HEGB) and low-energy grain boundary (LEGB) in large-angle grain boundary (LAGB), and they demonstrated different migration behaviors at the early and later stages. The behaviors of small-angle grain boundary (SAGB), including its migration and grains’ rotation, were also studied. Two different mechanisms of dislocation emission and absorption were explored, which demonstrates the possibility of dislocation elevating interfacial energy. The simulated results on the topological transition of grain boundaries prompted us to propose the thinking about the applications of the Neumann–Mullins law and Euler formula.

Graded Cladding Layers in Infrared III-Arsenide Separate Confinement Heterostructure Laser Diodes

Graded aluminum composition in AlGaAs n-cladding and p-cladding layers have been shown to exhibit improved optoelectronic performance in the single quantum well separate confinement heterostructure laser diode (SQW SCH LD) in the infrared region. The output power of the laser diode is increased up to 45 mW by using graded aluminum composition in n-/p- cladding layers. In addition, the lasing threshold current density is also lowered which results in a significant optical gain. The stimulated emission rate also improves due to improved electron-hole recombination and, thus, resulting in improved lasing.

Effects of different artificial photosynthetically active radiation (PAR) sources and intensity on the growth and nutrient uptake in Ulva prolifera and Neopyropia yezoensis

Fluorescent lamps and semiconductor light-emitting diodes (LEDs) lamps are commonly used as artificial light sources in the indoor algae cultivation system. In this study, we tested the effect of two types of fluorescent lamps (T8 and T5) and white LED lamp on the growth, photosynthesis, and nutrient uptake rates of Neopyropia yezoensis and Ulva prolifera under three photosynthetically active radiation (PAR) conditions (80, 150 and 300 μmol photon m2 s−1). White LED and T8 fluorescent light induced the highest and the lowest growth rates, respectively, in both species under each PAR. The effect of T5 fluorescent light on growth rate depends on the species and PAR. Interestingly, the T8 fluorescent light significantly increased the uptake rate of phosphorus under all PARs and nitrogen uptake rate was enhanced under 150 μmol photon m2 s−1 in U. prolifera, which was not observed in N. yezoensis. Our results suggest that white LED lamp is a more economical and efficient artificial light source than fluorescent lamps because of their highest enhancement of growth. The optimal PAR of T5 fluorescent light for growth is lower than T8 fluorescent light in the cultivation of U. prolifera. T8 fluorescent increases phosphorous uptake rate in U. prolifera.