Diode Current Research Articles

Surface-barrier photoconverters with graded-gap layers in the space-charge region

A novel possibility of controlling the parameters of p-Cu1.8S-n-II-VI surface-barrier structures by embedding a thin graded-gap layer into a photoconverter space-charge region (SCR) is implemented. The feature of quasi-electric fields built in the SCR, i.e., the fact that an increase in the drift field for minority carriers can be accompanied by a decrease in the potential barrier for majority carriers, is considered. The proper choice of the parameters of the Cd x Zn1 − x S graded-gap layer embedded in the Cu1.8S-ZnS structure SCR made it possible to double the quantum efficiency in the ultraviolet spectral region. For Cu1.8S-CdS photoconverters with a (CdS) x (ZnSe)1 − x intermediate layer, dark diode currents are decreased by three orders of magnitude while retaining a high quantum efficiency.

X-ray topographic study of defect in p− diamond layer of Schottky barrier diode

Semiconducting diamond has received significant attention as a material for use in power devices owing to its high breakdown characteristics and high carrier mobility in high-temperature, high-voltage environments. Several research groups have postulated that the density of defects is a critical issue for the development of high-performance devices. In addition, they have suggested that a high-quality crystal with a flat surface and a low defect density is required for achieving high and stable performance.In this study, we investigated the reverse leakage current of some Schottky barrier diodes and the defect distribution in the area of each Schottky electrode by using X-ray topography.

Medium Voltage Resonant Converter with Balanced Input Capacitor Voltages and Output Diode Currents

This paper presents a 1.92 kW resonant converter for medium voltage applications that uses low voltage stress MOSFETs (500V) to achieve zero voltage switching (ZVS) turn-on. In the proposed converter, four MOSFETs are connected in series to limit the voltage stress of the power switches at half of the input voltage. In addition, three resonant circuits are adopted to share the load current and to reduce the current stress of the passive components. Furthermore, the transformer primary and secondary windings are connected in series to balance the output diode currents for medium power applications. Split capacitors are adopted in each resonant circuit to reduce the current stress of the resonant capacitors. Two balance capacitors are also used to automatically balance the input capacitor voltage in every switching cycle. Based on the circuit characteristics of the resonant converter, the MOSFETs are turned on under ZVS. If the switching frequency is less than the series resonant frequency, the rectifier diodes can be turned off under zero current switching (ZCS). Experimental results from a prototype with a 750-800 V input and a 48V/40A output are provided to verify the theoretical analysis and the effectiveness of the proposed converter.

Improved GaN films with low background doping and low deep trap density grown by hydride vapor phase epitaxy

AbstractElectrical properties and deep electron and hole traps spectra are compared for undoped n‐GaN films grown by hydride vapor phase epitaxy (HVPE) on sapphire substrates at 850 °C (Group 1) and 950 °C (Group 2). Group 1 samples have very low residual donor concentration ((2‐5)×1014 cm‐3), very low density of electron and hole traps, low leakage current of Schottky diodes. Group 2 samples are not very different from the usual thick HVPE samples in terms of predominant electron and hole traps and MCL spectra. But the concentration of both electron and hole traps is quite high and could contribute to rather high reverse leakage current, low photocurrent and pronounced tunneling. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Broadband Optical Receiver IC on InP

The principals of optical communication systems operating at 10 Gbps and more are presented at this paper. A Transimpedance Amplifier (TIA) is the main part here. The Photo Diode current is a single input signal for TIA, and the differential voltage is the TIA output signal. A several ways to provide a reference voltage (biasing) to the second input of differential stage are inspected. The mostly suitable solution in case of 10 Gbps TIA designed on InP process is the using of a feedback loop with external operation amplifier. The good performance of such TIA was demonstrated using simulations with cadence tool. TIA ICs designed on InP process look promising due to advantages, which goes to be important with the growth of communication speed. These are high transistor bandwidth and the possibility of integrating the photodiode and TIA on the same chip, what reduces noises and signal distortions. This lets to foretell the optical receiver IC on InP process will be used at 10…40 Gbps area. Ill. 2, bibl. 5 (in English; summaries in Lithuanian, English and Russian).

An Improved Single-Phase Active-Front-End Rectifier System for Use With Three-Phase Variable-Frequency Drives

In many rural areas, due to unavailability of three-phase ac power, three-phase variable-frequency drives (VFDs) are often required to operate from a single-phase ac source. Powering up three-phase VFDs from single-phase ac source requires addressing many issues: higher RMS value of input diode current, higher ripple voltage across the dc bus capacitor, higher peak input current, higher input current distortion, lower power factor, and poorer system efficiency. All of these lead to severe derating of VFDs for single-phase applications. A new low-cost single-phase active circuit based on injecting current into the midpoint of the dc bus employing only one bidirectional switch is proposed here. The bidirectional switch carries current for less than a quarter cycle and is rated accordingly. The presence of a three-phase diode bridge rectifier lends itself to better distribute the higher input root-mean-square current so that the diodes need not carry current higher than their nominal rating. The proposed method shows that VFDs need not be derated to achieve rated output power. Test results from a 15-hp 230-V system are given to prove the concept.

A novel nanoscale low-voltage SOI MOSFET with dual tunnel diode (DTD-SOI): Investigation and fundamental physics

In this paper, critical electrical characteristics of a nanoscale low-voltage partially-depleted silicon-on-insulator (PD-SOI) MOSFET have been improved in terms of floating body effect, short channel effects, subthreshold swing, leakage current, self-heating effect, voltage gain, parasitic bipolar device effect, parasitic capacitance, and unilateral power gain. The heart of the proposed structure is a dual tunnel diode formed by a heavily doped P-type L-shaped trench. The accumulated holes are effectively released by the tunnel current of the dual tunnel diode. The proposed structure is found to be free of kink effect. Other substantial parameters of the proposed structure have been improved owing to L-shaped trench. Comparing the proposed structure with a conventional SOI (C-SOI), the proposed structure is considered as an undeniable contender in nanoscale integrated applications.

Green electroluminescence from p-ZnO:N/n-GaN heterojunction light-emitting diodes

A p-ZnO:N/n-GaN heterojuction light emitting diode was successfully constructed by thermal oxidation of Zn3N2 film which was deposited on n-type GaN substrates by N-plasma assisted pulsed laser deposition technology. The p-ZnO:N/n-GaN light emitting diode showed a typical diode current–voltage (I–V) characteristic and an electroluminescence emission of 517 nm was observed. This green electroluminescence emission came from the p-ZnO:N layer, which was confirmed by analyzing the results of x-ray diffraction, I–V measurement and electroluminescence spectra comprehensively.

Domain switching kinetics in ferroelectric-resistive BiFeO3 thin film memories

We fabricated (00l) BiFeO3 (BFO) thin films in different growth modes on SrRuO3/SrTiO3 substrates using a pulsed laser deposition technique. X-ray diffraction patterns show an out-of-plane lattice constant of 4.03 Å and ferroelectric polarization of 82 µC/cm2 for the BFO thin film in a layer-by-layer growth mode (2D-BFO), larger than 3.96 Å and 51 µC/cm2 for the thin film in the 3D-island formation growth mode (3D-BFO). The 2D-BFO thin film at 300 K shows switchable on/off diode currents upon polarization flipping near a negative coercive voltage, which is nevertheless absent from the above 3D-BFO thin film. From a positive-up–negative-down pulse characterization technique, we measured domain switching current transients as well as polarization–voltage (Pf–Vf) hysteresis loops in both semiconducting thin films. Pf–Vf hysteresis loops after 1 µs-retention time show the preferred domain orientation pointing to bottom electrodes in a 3D-BFO thin film. The poor retention of the domains pointing to top electrodes can be improved considerably in a 2D-BFO thin film. From these measurements, we extracted domain switching time dependence of coercive voltage at temperatures of 78–300 K. From these dependences, we found coercive voltages in semiconducting ferroelectric thin films much higher than those in insulating thin films, disobeying the traditional Merz equation. Finally, an equivalent resistance model in description of free-carrier compensation of the front domain boundary charge is developed to interpret this difference. This equivalent resistance can be coincidently extracted either from domain switching time dependence of coercive voltage or from applied voltage dependence of domain switching current, which drops almost linearly with the temperature until down to 0 in a ferroelectric insulator at 78 K.

Use of a radial self-field diode geometry for intense pulsed ion beam generation at 6 MeV on Hermes III

We investigate the generation of intense pulsed focused ion beams at the 6 MeV level using an inductive voltage adder (IVA) pulsed-power generator, which employs a magnetically insulated transmission line (MITL). Such IVA machines typical run at an impedance of few tens of Ohms. Previous successful intense ion beam generation experiments have often featured an “axial” pinch-reflex ion diode (i.e., with an axial anode-cathode gap) and operated on a conventional Marx generator/water line driver with an impedance of a few Ohms and no need for an MITL. The goals of these experiments are to develop a pinch-reflex ion diode geometry that has an impedance to efficiently match to an IVA, produces a reasonably high ion current fraction, captures the vacuum electron current flowing forward in the MITL, and focuses the resulting ion beam to small spot size. A new “radial” pinch-reflex ion diode (i.e., with a radial anode-cathode gap) is found to best demonstrate these properties. Operation in both positive and negative polarities was undertaken, although the negative polarity experiments are emphasized. Particle-in-cell (PIC) simulations are consistent with experimental results indicating that, for diode impedances less than the self-limited impedance of the MITL, almost all of the forward-going IVA vacuum electron flow current is incorporated into the diode current. PIC results also provide understanding of the diode-impedance and ion-focusing properties of the diode. In addition, a substantial high-energy ion population is also identified propagating in the “reverse” direction, i.e., from the back side of the anode foil in the electron beam dump.

Optimization of SVM Classifier by k-NN for the Smart Diagnosis of the Short-Circuit and Impedance Faults in a PV Generator

This paper deals with a new algorithm allowing short-circuit and impedance faults smart diagnosis of PV generators. It is based on the use of the SVM technique for the classification of observations not located in its margin, otherwise the proposed algorithm is used a k-NN method. A PV generator database containing observations distributed over classes is used for testing the new algorithm performance, which shows therefore its contribution and its effectiveness in the diagnosis area. * Parameter j of new observation x *. I' Identity matrix. J Tuning parameter for error accepted. I Current. V Voltage. P Power. PH Photocurrent. I/V Cell Current / Voltage of PV cell. I/V Group Current / Voltage of PV group. I/V Module Current / Voltage of PV module. I/V String Current / Voltage of PV string. I Bypass_Diode Bypass diode current. R s series resistance. t Temperature.

DFB laser diode interferometer with image capture timing control for surface profile reconstruction

A DFB laser diode interferometer with sinusoidal phase modulation (SPM) and image capture timing control was proposed for the reconstruction of surface profile. Sinusoidal phase modulation was achieved by controlling the injection current of light diode. The surface profile was reconstructed on four consecutive fringe images. Random phase error and low-frequency phase shift would be superposed on the interference fringes due to external disturbances such as mechanical vibration and temperature fluctuation. A simple peak detection circuit that would take less time consumption than phase generated carrier (PGC) was built for eliminating external disturbances, and the phase of fringe image could be stabilized in about one millisecond, which is conducive to real-time surface profile reconstruction. A novel method to capture four consecutive fringe images in adjacent modulation period was presented by controlling pulse sequence to trigger camera exposure and image readout operation. The whole system was tested on an optical table without vibration isolation and being kept in thermostatic chamber. The repeatability was about 0.018 wave (approximately 14nm for 760nm wavelength). The feasibility for high-resolution surface profile reconstruction had been verified.

Design of an <inline-formula> <tex-math notation="TeX">\(X\) </tex-math></inline-formula>-Band Gigawatt Multibeam Relativistic Klystron Amplifier

To achieve gigawatt-level amplification output radiation in \(X\) -band, an \(X\) -band coaxial multibeam relativistic klystron amplifier is designed. When the diode voltage and diode current are increased to obtain higher output power, higher modes can seriously degrade Klystron performance and cause pulse shortening. Special measures are introduced in the device to suppress the higher mode excitation and avoid pulse shortening. Finally, pulse shortening is avoided in the coaxial multibeam relativistic Klystron amplifier. Output power of 2.1 GW with an efficiency of 40% is obtained in the particle-in-cell simulation when driven microwave power is only several kilowatts.

Efficiency and stability of a phosphor-conversion white light source using a blue laser diode

A white light source using direct phosphor-conversion excited by a blue laser diode is presented. In this preliminary study we have investigated the influence of phosphor’s thickness and operating current of the laser diode over the (x, y) chromaticity coordinates, Correlated Color Temperature (CCT) and Color Rendering Index (CRI). The best values found were 4000 K and 94. A 40 lm/W luminous efficacy was achieved together with a CRI close to 90 for an operating current of 0.8 A. Those values, to the best of our knowledge, were not previously reported in the literature.

Study of the relaxation of the excess current in silicon Schottky diodes

This study is devoted to investigation of the relaxation of excess current in silicon α-NiTi-n-Si Schottky diodes subjected to either γ-ray radiation or local disturbance of the interface structure using a diamond indenter. A decrease in the excess diode current is attained using both thermal annealing and ultra-sound irradiation. Simultaneously, the parameters of solar cells manufactured from the above-mentioned Schottky diodes subjected to irradiation with γ-ray photons and to single or double irradiation with ultra-sound are studied. It is shown that, after the effect of the diamond indenter, the excess current decreases as a result of thermal annealing; however, a decrease in the excess current to the initial value is not attained. The photoelectric parameters of the studied solar cells before irradiation and after irradiation with γ-ray photons and after single or double irradiation with ultrasound show that ultrasonic treatment is more efficient than thermal annealing.

Implementation of a DC-Side Class-DE Low-<formula formulatype="inline"><tex Notation="TeX">$\bm{d\upsilon/ dt}$</tex> </formula> Rectifier as a PFC for Electronic Ballast Application

An analysis and design of a single-stage electronic ballast with a dc-side Class-DE low- $d\upsilon/dt$ resonant rectifier is studied in this paper to improve a poor power-factor and low line harmonic. The power-factor correction is achieved by utilize an output characteristics of a Class-DE rectifier, which is inserted between the front-end bridge rectifier and the bulk-filter capacitor. The design procedure is based on the principle of the Class-DE rectifier, which also ensures more accurate results and the proposed scheme provided a more systematic and feasible analysis methodology. The active switches can be operated under the soft-switching condition. By employing an electromagnetic interference filter after bridge rectifier, the standard-recovery diode for bridge rectifier can be employed, the cost can be reduced, the conduction angle of the bridge-rectifier diode current was increased, and low line harmonic distortion and a power factor near unity were achieved. The dc-side Class-DE rectifier is driven by a high-frequency current source, which is obtained from the square-wave output voltage of the Class-D series–parallel resonant inverter through an LC-series circuit. A prototype of the ballast, operating at an 84-kHz fixed frequency and a 220-V $_{\rm rms}$ , 50-Hz line voltage, was utilized to drive a T8–36 W fluorescent lamp. The validity of this approach was confirmed by simulation and experimental results.

Shallow donor and deep DX-like center in InAlN layers nearly lattice-matched to GaN

Nonintentionally doped 200-nm-thick ${\mathrm{In}}_{0.16}{\mathrm{Al}}_{0.84}\mathrm{N}/{n}^{+}\text{\ensuremath{-}}\mathrm{GaN}$ samples were grown by metal-organic vapor phase epitaxy and used for the electrical characterization of InAlN. In the temperature range 180--400 K, the forward current of Schottky diodes is dominated by a tunneling mechanism below 1.2 V. Capacitance and conductance-temperature characteristics were measured at 1 MHz in the 90--400 K range and at various voltages. The conductance vs temperature reveals two peaks ${\mathrm{D}}_{1}$ and ${\mathrm{D}}_{2}$, which are attributed to bulk states in InAlN. Their characterization by admittance spectroscopy gives thermal activation energies of $\ensuremath{\approx}68$ meV and 290 meV, and thermal capture cross section of $9.7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}17}$ ${\mathrm{cm}}^{2}$ and $\ensuremath{\approx}6.2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}15}$ ${\mathrm{cm}}^{2}$, respectively. The same levels are also revealed by extracting the temperature dependence of the carrier density in the neutral region of InAlN from $I\text{\ensuremath{-}}V\text{\ensuremath{-}}T$ characteristics on the Schottky diode. A partial carrier freeze out is demonstrated and discussed in the framework of an existing theory for DX centers. The use of this approach is supported by the evidence of persistent photoconductivity effects, which strongly indicate the presence of DX centers in our material. It results that each donor in InAlN would exist in two distinct lattice configurations, a substitutional one (${\mathrm{D}}_{1}$, hydrogenic state) and a lattice-distorted one (${\mathrm{D}}_{2}$, DX state). From secondary ion mass spectrometry data, theoretical grounds, and previous experimental evidence in the $\mathrm{Al}{}_{x}\mathrm{Ga}{}_{1\ensuremath{-}x}\mathrm{N}$ system, oxygen is the most probable candidate for such an unintentional dopant.

Infinite Output Resistance of Corbino Thin-Film Transistors With an Amorphous-InGaZnO Active Layer for Large-Area AMOLED Displays

We report a low-voltage-driven amorphous indium-gallium-zinc oxide (a-IGZO) semiconductor-based Corbino (circular) thin-film transistor (TFT) with infinite output resistance beyond pinchoff. The Corbino TFT has inner and outer concentric ring electrodes, and when the latter is the drain, channel width (W) decreases with channel length (L), such that the W/L ratio is not changed after pinchoff. As demonstrated herein, this a-IGZO Corbino TFT is, therefore, a good candidate for uniform current drivers in applications, such as active-matrix organic light-emitting diode display pixels, where it would maintain the same drive (diode) currents, even with variations in supply voltage (V DD ).

Class-D Zero-Current-Switching Rectifier as Power-Factor Corrector for Lighting Applications

An analysis and design of a zero-current-switching (ZCS) Class-D current-source driven rectifier for the lighting applications is presented, which is one of the resonant rectifiers as a power-factor corrector to improve a poor power-factor and high line current harmonic of a single-stage converter. A high power-factor is achieved by the utilization of output characteristics of a Class-D ZCS rectifier, which is inserted between the front-end bridge rectifier and the bulk-filter capacitor. The conduction angle of the bridge rectifier diode current was increased and a low-line current harmonic and a power-factor near unity can be obtained. The design procedure is based on the principle of the Class-D ZCS rectifier, which also ensures more accurate results and the proposed scheme provides a high efficiency and a more systematic and feasible analysis methodology. The active switches can be operated under the soft-switching condition. The validity of this approach was confirmed by simulation and experimental results.

A new approach to investigate leakage current mechanisms in infrared photodiodes from illuminated current-voltage characteristics

This paper presents a new approach to investigate leakage current mechanisms in infrared photodiodes from the illuminated current–voltage characteristics. The example of mid-wave mercury cadmium telluride photodiodes is presented to illustrate the new approach. The new method is suitable for evaluating diodes in an array environment as advance knowledge of any of the material or device parameters are not required. The thermal saturation current is estimated from the observed open circuit voltage and zero-bias current (photo-current) of the diode. The ohmic shunt resistance is estimated from the observed maximum dynamic impedance of the diode. The experimentally observed reverse bias diode current in excess of thermal current, photo-current, and ohmic shunt current is reported to be best described by an exponential function of the type, Iexcess = Ir0 + K1 exp (K2 V), where Ir0, K1, and K2 are fitting parameters and V is the applied bias voltage. Our investigations reveal a close link between the excess current and the sources of ohmic currents in the diode. Exponential growth of excess current with the applied bias voltage has been interpreted as an indication of soft breakdown of the diodes.