Diode Behavior Research Articles

Impact of Laser‐Induced Graphitization on Diamond Schottky Barrier Diodes

Pseudovertical Schottky barrier diodes (SBDs) are fabricated on a single‐crystal diamond substrate. Herein, the structural and electrical influence of laser‐induced graphitization which takes place during the laser‐dicing process is investigated. Before laser irradiation, the fabricated SBDs show a high rectifying ratio of more than 11 orders at ±10 V and undetectable leakage current. Ideality factor (n) and Schottky barrier height (ϕ b) are estimated to be 1.09 and 1.35 eV, respectively. After laser irradiation, the SBDs still exhibit good diode behavior, in which n and ϕ b values slightly change by 10%. Leakage current is increased about two orders of magnitude and breakdown voltage is degraded from 940 to 375 V due to the presence of graphite debris. After removing the graphite debris utilizing the oxygen plasma cleaning process through an inductively coupled plasma (ICP) system, all SBDs are recovered back to typical diode characteristics. It is found that strain and surface defects that may be introduced during laser dicing and post‐ICP etching do not severely influence SBD characteristics.

Enhancement of the light extraction characteristics and wide-angle emissive behavior of deep-ultraviolet flip-chip light-emitting diodes by using optimized optical films.

We propose the use of optical films to enhance the light extraction efficiency (LEE) and wide-angle emission of traditional packaged deep-ultraviolet light-emitting diodes (DUV-LEDs). Total internal reflection occurs easily in DUV-LEDs because they contain sapphire, which has a high refractive index. DUV-LEDs also contain an aluminum nitride (AlN) ceramic substrate, which has high light absorption in the ultraviolet band. Photons are absorbed by the sapphire and AlN ceramic substrate, which reduces the LEE of DUV-LEDs. By adding a brightness enhancement film (BEF) on the sapphire surface and a high-reflection film (HRF) on the surface of the AlN ceramic substrate, the LEE of DUV-LEDs can be increased. Moreover, we designed a single-layer metal reflective film (SMRF) on the upper surface of the quartz glass in order to achieve wide-angle emission. Experimental results indicated that compared with traditional packaged DUV-LEDs, the light output power and external quantum efficiency of DUV-LEDs with a plated BEF, HRF, and SMRF increased by 18.3% and 18.2%, respectively. Moreover, an emission angle of 160° was achieved. In a reliability test, DUV-LEDs maintained more than 95% of the initial forward voltage and light output power after 1000 h of operation at 25°C, which indicated that the addition of an optical film can improve the light efficiency and long-term reliability of DUV-LEDs.

Direct detection of electronic states for individual indium arsenide (InAs) quantum dots grown by molecular beam epitaxy

Indium arsenide (InAs) quantum dots (QDs) have been characterized using a conductive-mode atomic force microscope (C-AFM), where a well-defined gold-coated AFM probe has been used to electrically probe each individual QD. The InAs QDs were grown on a gallium arsenide (GaAs) substrate in a self-assembled manner by using molecular beam epitaxy (MBE). The measured current-voltage (I-V) curves of individual QDs exhibit a typical Schottky diode behavior, which can be attributed to the metal/semiconductor junction between the AFM gold probe and the n-doped GaAs bulk. However, distinct I-V curves are observed in sequential measurements, where a less forward turn-on voltage is measured in the subsequent voltage sweeps compared to the initial sweep. However, this effect is not evident when the same measurements are conducted on a plane surface (in the absence of QDs) on the same substrate. The discrete voltage values at the forward bias on a QD indicates a change in the electronic states due to trapped electrons in the QD during the initial voltage sweep. These unique characteristics of QDs can be exploited for potential applications in fast-response data storage devices and quantum computing.

Comparison of electrical characteristics of Schottky junctions based on CdS nanowires and thin film

CdS nanowires and film Schottky diodes are fabricated and diode properties are compared. Effect of SnO2 on CdS film diode properties is investigated. CdS film/Au on 100 nm SnO2 substrate demonstrates like-resistor characteristics and increase in SnO2 thickness corrects resistor behavior, however the effective reverse saturation current density J o is significantly high and shunt resistance are considerably low, implying that SnO2 slightly prevents impurities migration from CdS films into ITO but cause additional issues. Thickness of CdS film on diode properties is further investigated and increasing CdS film thickness improved J o by one order of magnitude, however shunt resistance is obviously low, suggesting intrinsic issues in CdS film. 100 nm CdS nanowire/Au diodes reduce J o by three orders of magnitude in the dark and two orders of magnitude in the light respectively and their shunt resistance is significantly enhanced by 70 times when comparing with those of the CdS film diodes. The wide difference can be attributed to the fact that CdS nanowires overcome intrinsic issues in CdS film and thus demonstrate significantly well- defined diode behavior. Simulation found that CdS nanowire diodes have low compensating acceptor type traps and interface state density of 5.0 × 109 cm−2, indicating that interface recombination is not a dominated current transport mechanism in the nanowire diodes. CdS film diodes are simulated with acceptor traps and interface state density increased by two order of magnitude and shunt resistance reduced by one order of magnitude, indicating that high density of interface states and shunt paths occur in the CdS film diodes.

FABRICATION OF THE P-N JUNCTION ULTRAVIOLET PHOTODETECTORS BASED ON METAL OXIDE NANOPARTICLES

Recently, wide bandgap metal oxides have attracted tremendous attention in the field of UV photodetectors due to their promising optoelectronic properties. Up to now, various approaches have been used to design metal oxide-based UV photodetectors. Among these designs, p-n junction UV photodetectors exhibited remarkable performance. In this study, TiO2/CuCrO2 p-n junction as a UV photodetector was fabricated with spin coating method for the first time. The morphological and optical properties of the fabricated devices were investigated in detail. Moreover, the effect of the CuCrO2 thickness on the performance of the UV photodetector was explored. The fabricated devices showed promising diode behavior and UV response. The responsivity (R) and specific detectivity (D*) of the best device were 3.11 mA/W and 2.37x1011 Jones, respectively at -1.5 V under 3 mW/cm2 light intensity.

Insights into thermal characteristics of spiral carbon-based nanomaterials: From heat transport mechanisms to tunable thermal diode behavior

The discovery of new ways and new materials to control heat transfer has always received significant attention. Carbon-based nanomaterials due to their outstanding thermal characteristics have been a promising candidate for thermal transport and thermal rectification. A man-made spiral carbon-based nanomaterial (SCBN) possesses unique geometry characteristics and mechanical response gaining immense popularity for usage in nanodevices and nanocomposites. Using molecular dynamics simulation, thermal conductivity and thermal rectification of SCBNs have been scrutinized considering different geometry, hydrogenation effect, and mechanical response. Results show that the thermal conductivity of SCBN is utterly depended on geometry properties and heat direction; thus, thermal conductivity has obtained a wide variety from 4.1 W/mK to 45.4 W/mK. In addition, the gradient, full/pristine, and 30%hydrogenation/pristine of graphene helicoid (GH), as a special type of SCBNs, influence thermal rectification. Also, the results affirm a sharper increase in the hydrogenation ratio leads to higher thermal rectification. Interestingly, the strain has a remarkable impact on the thermal rectification which changes from 18.1% to 51.5% for the 30%/pristine hydrogenated GH. Our result revealed that tunning heat transfer is completely possible by applying strain. Thus, SCBNs benefited from inherent novel properties have a great potential for usage in thermal management applications.

Hydrothermal fabrication of p‐Cu2O−n‐ZnO films and their properties for photodegradation and ultraviolet sensors

AbstractThis article reports spin coating and hydrothermal approaches to the synthesis of Cu2O seed layer−ZnO and Cu2O film−ZnO heterojunction films on fluorine‐doped tin oxide substrates. Cu2O seed layers and an ethylene glycol (EG) reducing agent were employed to obtain pure, uniform, and adhesive Cu2O films on the substrate. Transmission electron microscopy validated the heterojunctions with clear interfaces between each component on the p‐Cu2O film−n‐ZnO (with EG) sample, the conductive types of which were determined through Mott−Schottky measurements. Constructed energy band diagrams supported the Mott−Schottky result, manifesting favorable conduction band positions for the generation of •O2− radicals for all constituent materials and indicating smooth charge carrier transport for the p‐Cu2O film−n‐ZnO (with EG) sample. Furthermore, abundant p−n junction interfaces synergistically enabled the sample to exhibit the most satisfactory photodegradation capability (rate constant ≈ 8.9 × 10−3 min−1), which was attributable to the predominance of •OH radicals. The sample's rectifying (diode) behavior with a ratio of the current density (J) at +3 V (forward bias) to that at −3 V (reverse bias) of approximately 27 was observed without ultraviolet illumination. Moreover, the J at −3 V is under illumination approximately 80 times that without illumination, implying the suitability of the sample for UV detectability.

Characterization of self-magnetic pinch radiographic diode performance on RITS-6 at Sandia National Laboratories. II. Coupling between the inductive voltage adder and the SMP load

The self-magnetic pinch (SMP) diode is a type of radiographic diode used to generate an intense electron beam for radiographic applications. At Sandia National Laboratories, SMP was the diode load for the six-cavity radiographic integrated test stand inductive voltage adder (IVA) driver operated in a magnetically insulated transmission line (MITL). The MITL contributes a flow current in addition to the current generated within the diode itself. Extensive experiments with a MITL of 40 Ω load impedance [T. J. Renk et al., Phys. Plasmas 29, 023105 (2022)] indicate that the additional flow current leads to results similar to what might be expected from a conventional high-voltage interface driver, where flow current is not present. However, when the MITL flow impedance was increased to 80 Ω, qualitatively different diode behavior was observed. This includes large retrapping waves suggestive of an initial coupling to low impedance as well as diode current decreasing with time even as the total current does not. A key observation is that the driver generates total current (flow + diode) consistent with the flow impedance of the MITL used. The case is made in this paper that the 80 Ω MITL experiments detailed here can only be understood when the IVA-MITL-SMP diode is considered as a total system. The constraint of fixed total current plus the relatively high flow impedance limits the ability of the diode (whether SMP or other type) to act as an independent load. An unexpected new result is that in tracking the behavior of the electron strike angle on the converter as a function of time, we observed that the conventional cIVx “Radiographic” radiation scaling (where x ∼ 2.2) begins to break down for voltages above 8 MV, and cubic scaling is required to recover accurate angle tracking.

Fabrication of CeO2/CuI thin film with CdO as a buffer – A heterojunction diode

Solar photovoltaics has remained a popular field despite the availability of a number of renewable energy technologies to meet global energy demands due to its ease of manufacture, materials availability, use, and low cost. In the current investigation, CuI was synthesized with the extract of Hibiscus rosa-sinensis L. flower and CeO2 & CdO were synthesized using citrate-nitrate sol-gel method. The obtained crystals were characterized using XRD, HR-TEM, HR-SEM, EDAX, UV–Vis and FTIR spectroscopic techniques. The XRD analysis of the synthesized compounds confirmed their high crystallinity and purity. The particle size of CuI, CeO2 and CdO was found to be 503.77 nm, 18.51 nm, 15.1 nm respectively from HR-TEM analysis. The CuI particles were prismatic and CeO2 & CdO were spherical in nature under HR-SEM. The band gap was calculated to be 3.03 eV for CuI, 3.43 eV for CeO2 and 2.03 eV for CdO from the UV data. The cyclic voltammetry analysis indicated that the synthesized compounds possess good electrochemical properties. CeO2/CuI heterojunction was fabricated as thin film by doctor blade method and effect of employing CdO as buffer layer was studied. The following heterojunctions - FTO/CeO2/CuI/Ag (p-n heterojunction) and FTO/CeO2/CdO/CuI/Ag (p-n-n heterojunction) were fabricated. The current-voltage (I–V) curve revealed that CeO2/CuI heterojunction exhibits better diode behavior in the presence of CdO as a buffer layer with low positive rectification ratio. Thus, with a better fabrication technique the synthesized semiconductor materials could be suitable for application in energy harvesting technology.

Charge Accumulation Behavior in Quantum Dot Light-Emitting Diodes

Charge Accumulation Behavior in Quantum Dot Light-Emitting Diodes

Asymmetric heterojunctions between size different 2D flakes intensify the ionic diode behaviour.

Here we report on the facile formation of asymmetric heterojunctions between laterally size different 2D flakes, which leads to a prominent gradient in charge distribution at the nanocontact interface and triggers ionic diode-like transport behaviour with a rectification ratio of 110.

GaN Active Rectifier Diode

Active or synchronous rectification is used today to further increase the efficiency of mass-market power supplies by eliminating the turn-on voltage of rectifier diodes, thus reducing conduction losses. However, the active rectification is usually realized by two devices: a power MOSFET and a control circuit to imitate an ideal diode behavior. This paper presents a GaN active rectifier diode consisting of a 600 V power transistor, a control circuit with gate driver, and a supply generation, all monolithically realized in a GaN power integrated circuit (IC). This enables a true two-terminal device that can directly replace a rectifier diode. In order to evaluate the proposed conduction loss reduction by replacing a rectifier diode by an active diode, the theoretical limits at circuit level and at semiconductor level are analyzed. The GaN active rectifier diode is demonstrated in a half-wave rectification (110/230 V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">AC</sub> , 50/60 Hz) up to a forward current of 6 A. A single-device realization of low-loss GaN active rectifier diodes is more cost-efficient than a multi-chip or package-integrated solution.

Coupled Current Jumps and Domain Wall Creeps in a Defect‐Engineered Ferroelectric Resistive Memory

AbstractFerroelectric (FE) resistive switching has attracted considerable interest as a promising candidate for applications in non‐volatile memory technology. In this work, via judiciously controlling the defect states of oxygen vacancy through Sm‐doping, the authors obtain multiple current jumps/discrete resistance states in the resistive switching memories based on a model FE BiFeO3 (BFO). These hitherto unreported current jumps are attributed to the space‐charge‐limited current correlated with electron trapping by oxygen vacancies in the BFO film. Concurrently, oxygen vacancies serve as the pinning centers for the FE domains, leading to the domain wall creep behavior. These results illustrate the strong interplay between the defect, resistive switching, and domain wall creep behavior in FE diodes, providing a new insight into the mechanism of FE resistive switching. Overall, the large on/off ratio of ≈5 × 105, multiple resistance states, and fast switching speed of ≈30 ns, promise their potential applications in multi‐level data storage memories.

Tunable Current Regulative Diode Based on Van der Waals Stacked MoS2/WSe2 Heterojunction–Channel Field‐Effect Transistor

AbstractField‐effect transistors (FETs) are the main building block of microelectronic devices. For most of the FETs, the conduction channel relies on either n‐type or p‐type semiconductor materials. Recent advances in 2D materials offer an opportunity to form van der Waals heterojunction‐based FETs with novel electrical performance. Here, a MoS2/WSe2 heterojunction–channel FET using h‐BN as insulating layer and Cr/Au metal as the gate, is demonstrated. Two asymmetric Schottky contacts are formed at both sides of MoS2, WSe2 due to electron tunneling effects, work function differences, and Fermi level pinning. Benefiting from that, the authors observe a forward current regulating diode behavior, where the drain current remains unchanged regardless of the drain voltage (VDS) fluctuations and can be modulated by the gate voltage, atmosphere temperature, vacuum pressure, and h‐BN layer thickness. In addition, under higher VDS, heterojunction–channel breakdown induced by the Fowler–Nordheim (F–N) tunneling at the WSe2/h‐BN/metal region, is observed. Furthermore, the transistor demonstrates a reverse rectification behavior with onset voltage linearly depending on the temperature (3 mV T−1). This work paves the way for the potential application of heterojunction–channel FETs for high‐performance current regulator and current rectifier.

Diode and Active Negative Resistance Behaviors of Helminth Eggs as a Novel Identification/Differentiation Probe.

Helminths have always been studied as one of the critically annoying pathogens of parasite classes due to their adverse effects on the ecosystem of human life. They have the potency to negatively affect their hosts as points of disease, infection, cancer, and death, but in this study, we found interesting electronic properties in Fasciola hepatica, Parascaris equorum (with and without larvae), Dicrocoelium dendriticum, Taenia multiceps, and Moniezia expansa eggs. This claim is attributed to some surprising characteristics such as significant diode behavior [forward bias, 5.36–11.17 (±0.01) V, versus the ground, GND] and backward bias (−45.0 to −125.0 (±7.0) V, versus the GND) and highly active negative resistance (−2.59 to −7.11) × 1015 (±1.5) Ω in the AC mode. These traits were measured by the “blind patch-clamp, single-unit recording” methodology using a three-microelectrode system, implanted onto each tested egg under giga ohm sealed conditions (6.28 ± 0.02 GΩ cm–1 and n = 4). All the characteristic parameters were simultaneously attributed to the helminth egg structure by acceptable reproducibility (percentage of relative standard deviation: > 5%) and high enough rectitude with enough differentiation in their magnitudes, relatively. The reliability of these results was further confirmed using multiple calibrated techniques such as alternative/direct current voltammetry. Also, the significant role of water molecules as the key medium in creating these properties is evaluated qualitatively. In addition, the study aims at introducing these interesting parameters as a new approach to the fabrication of bio-based electronic elements, which are considered as a novel class of helminth egg-detection and -identification probes.

Upliftment the rectification behavior of PPy-WO3 nanocomposites for photodetector applications

In this study, PPy-WO3 nanocomposites were prepared with various amount of WO3 nanoparticles using in-situ chemical oxidative polymerization. The structure, surface morphology, functional, optical, electrical properties of PPy-WO3 nanocomposites remained categorized by several investigation approaches. The strong diffraction peak at 2θ = 25°, which confirms amorphous nature of PPy. WO3 confirms the major peaks at 2θ = 23.2°, 23.6°, 24.4° related to monoclinic phase. UV–Visible spectra of PPy and WO3 nanoparticles confirms the decreased band gap. The FESEM investigation elucidates the surface morphology of the samples. An endeavor has been made to fabricate the Ag/p-Si/PPy-WO3/Ag hybrid junction diodes using PPy-WO3 nanocomposites by a low-cost effective doctor-blade method also studied with current–voltage analysis in the dark and light circumstances. The mechanism of Ag/p-Si/PPy-WO3/Ag hybrid junction diode performance was explained in detail, current density (J) - voltage (V) technique is used to calculate the diode parameters. The excellent diode behavior is detected for 50 wt% weight percentage of WO3.

Synthesis, characterization and DFT study of new anthracene-based semiconducting polyethers for OLED application

New soluble semiconducting anthracene-based polyethers (An-BPS and An-TDP) were synthetized via the Williamson polycondensation of 9,10-dichloromethylanthracene with 4,4′-thiodiphenol (TDP) and bisphenol S (BPS), respectively. The polymers were investigated by density functional theory (DFT): the structural and optoelectronic properties, frontier molecular orbitals (HOMO/LUMO), as well as the infrared, absorption and fluorescence spectra were discussed. The polyethers structures were confirmed by NMR and FTIR spectroscopies, revealing good agreements between experimental and theoretical results. Quasi-identical absorption and blue emission properties were obtained for both polymers in dilute solutions, with a higher fluorescence efficiency for An-BPS. The cyclic voltammetry analysis of these electrochemically active materials showed a higher electron affinity for An-BPS and a lower ionization potential for An-TDP. The DFT calculations showed that the HOMO/LUMO frontier energy distributions are confined on the anthracene moiety in An-BPS. However in An-TDP, the LUMO distribution is localized on anthracene group, while the HOMO is on the TDP unit. The electric behavior of organic light-emitting diodes (OLEDs) based on these macromolecular structures has been investigated via numerical simulation using Silvaco TECAD software. Good electrical properties are estimated, with a low turn on voltages of 3.1 V and 2.9 V for An-TDP and An-BPS, respectively. However, An-BPS showed improved current conductivity, which makes it a good candidate for OLEDs.

Magnetic charge and geometry confluence for ultra-low forward voltage diode in artificial honeycomb lattice

Spin diode is important prerequisite to practical manifestation of spin electronics. Yet, a functioning magnetic diode at room temperature is still illusive. Here, we reveal diode-type phenomena due to magnetic charge mediated conduction in artificial honeycomb geometry, made of concave shape single domain permalloy element. We find that honeycomb lattice defies symmetry by populating vertices with low and high multiplicity magnetic charges, causing asymmetric magnetization, in applied current of opposite polarity. High multiplicity units create highly resistive network, thereby inhibiting magnetic charge dynamics propelled electrical conduction. However, practical realization of this effect requires modest demagnetization factor in constituting element. Concave structure fulfills the condition. Subsequently, magnetic diode behavior emerges across broad thermal range of T = 40 K–300 K. The finding is a departure from the prevailing notion of spin-charge interaction as the sole guiding principle behind spintronics. Consequently, a new vista, mediated by magnetic charge interaction, is envisaged for spintronic research.

Temperature analysis of driver and optical behavior of LED lamps

This exploratory study was carried out with the objective to know the optical behavior of light-emitting diode (LED) lamps used and the temperature reached by electronic components that compose the driver (electronic circuit situated inside the body LED lamp) responsible to convert electrical alternating current from power line to direct current to operate the LED devices. Then, two different experiments were carried out with LED lamps. In the first experiment, 131 LED lamps used were chosen randomly and bought from household appliances store (bargain market product) presenting different nominal powers, 8, 10, 12 and 15 watts. All LED lamps were polarized at the power line at 127 V and revealed different optical behaviors, such as: not turn-on; flashing light (as strobe effect); flashing light (as strobe effect) with high intensity (more intense than normal); flashing light (as strobe effect) with low intensity (less intense than normal); fast turnon and turn-off only; and turn-on with low intensity of light (less intense than normal). The hypothesis for these behaviors can be attributed by three different behaviors: in lamps not turn-on, this failure can be attributed for dark spots that are created on the surface of LED device. In these lamps, all LED devices are electrically connected in serial. When a LED is inoperative, the electrical current is interrupted for all LED devices; damage to the electronic components caused by internal high temperature confined inside the lamp body during the operation causing electrical oscillations, as observed from different behaviors from flashing light, flashing light with high intensity, flashing light with low intensity and fast turn-on and turn-off only; swelling of the electrolytic capacitors causing low energy storage and varying the electrical current flow, the electrical current for other electronic components altered the normal optical behavior of the LED lamps. In the second experiment, the temperatures of electronic components located in driver were obtained out of body lamp revealing: from 33 (lowest temperature attributed to inductor) to 52.5ºC (highest temperature attributed to electrolytic capacitor). These temperature values represent the ideal or normal condition of operation for electronic components, but, when they are operating inside the lamp body, the found temperature values increased considerably. This characteristic can be better evidenced by strong color change (caused by accumulative temperature during the elapsed days used) on the printed circuit board used in the driver.

Temperature analysis of driver and optical behavior of LED lamps

This exploratory study was carried out with the objective to know the optical behavior of light-emitting diode (LED) lamps used and the temperature reached by electronic components that compose the driver (electronic circuit situated inside the body LED lamp) responsible to convert electrical alternating current from power line to direct current to operate the LED devices. Then, two different experiments were carried out with LED lamps. In the first experiment, 131 LED lamps used were chosen randomly and bought from household appliances store (bargain market product) presenting different nominal powers, 8, 10, 12 and 15 watts. All LED lamps were polarized at the power line at 127 V and revealed different optical behaviors, such as: not turn-on; flashing light (as strobe effect); flashing light (as strobe effect) with high intensity (more intense than normal); flashing light (as strobe effect) with low intensity (less intense than normal); fast turnon and turn-off only; and turn-on with low intensity of light (less intense than normal). The hypothesis for these behaviors can be attributed by three different behaviors: in lamps not turn-on, this failure can be attributed for dark spots that are created on the surface of LED device. In these lamps, all LED devices are electrically connected in serial. When a LED is inoperative, the electrical current is interrupted for all LED devices; damage to the electronic components caused by internal high temperature confined inside the lamp body during the operation causing electrical oscillations, as observed from different behaviors from flashing light, flashing light with high intensity, flashing light with low intensity and fast turn-on and turn-off only; swelling of the electrolytic capacitors causing low energy storage and varying the electrical current flow, the electrical current for other electronic components altered the normal optical behavior of the LED lamps. In the second experiment, the temperatures of electronic components located in driver were obtained out of body lamp revealing: from 33 (lowest temperature attributed to inductor) to 52.5ºC (highest temperature attributed to electrolytic capacitor). These temperature values represent the ideal or normal condition of operation for electronic components, but, when they are operating inside the lamp body, the found temperature values increased considerably. This characteristic can be better evidenced by strong color change (caused by accumulative temperature during the elapsed days used) on the printed circuit board used in the driver.