Properties Of Diodes Research Articles

Optical-Emission Properties of GaN-Based Nanopillar Light-Emitting Diodes Prepared on Non-Polished and Non-Single-Crystalline Substrates

GaN-based nanopillar crystals are directly grown on multicrystalline Si and amorphous-carbon-coated graphite substrates whose surfaces are not mirror-polished. Light-emitting diodes (LEDs) of a double-hetero structure are prepared from the nanopillar crystals, and their optical–emission properties are investigated. Despite the substrate type and surface conditions, moderate light emissions are obtained from nanopillar LEDs though the light emissions are not always homogeneous, especially in the LEDs prepared on the graphite-based substrate. Nevertheless, these results will lead to realizations of novel large-area light-emitting devices.

Mechanical Motion Tuned Carrier Transport Characteristic of Dynamic Diode

AbstractSince the invention of the dynamic diode, its physical properties and potential applications have attracted wide attention. Lots of attempts are made to harvest the rebounding current and voltage of the dynamic diode. However, the underlying physical mechanism of its carrier transport characteristic is rarely explored carefully. Here, the electrical transport properties of the dynamic diode are systematically investigated with a mechanical motion‐tuned method, where the dynamic current‐voltage (I‐V) curve shows a gentler growth trend compared to the static curve. The rebounding current increases with motion velocity and contact force, resulting in a reduced current with the same bias voltage and an oscillation current with a changing velocity and force. This study shows a physical picture of adjusting microscopic carrier motion with macroscopic mechanical motion, which provides strong theoretical support for designing dynamic diode devices with better performance in the future.

Comprehensive investigation of sputtering deposition pressure effects on a-InGaZnO Schottky diodes

The effects of Ar sputtering deposition pressure on the optical, structural, morphological, and electrical properties of amorphous InGaZnO thin films were investigated. The InGaZnO thin films, which have amorphous structures determined by grazing incidence x-ray diffraction, contained In, Ga, Zn, and O confirmed by secondary ion mass spectrometry method. Additionally, when the thicknesses of the deposited thin films are examined, it was seen that the profilometer measurement results of the crater formed by secondary ion mass spectrometer and scanning electron microscope measurement results are nearly similar, and it is approximately 100 nm. The surface roughness, obtained from Atomic Force Microscopy results, show that decreased up to a particular value with the increase of the working pressure, and then the surface roughness increased. The optical band gaps of the films were obtained in the range of 3.50 eV−3.58 eV via Tauc relation by using the Ultraviolet-Visible measurements carried out in the wavelength range of 200 nm−1100 nm. It was seen that the optical band gap was decreased with the increase in Ar pressure. The electrical properties of InGaZnO thin film-based Schottky diodes, such as the barrier height, ideality factor, saturation current, series resistance, and shunt resistance, have also been studied comprehensively. The electrical results showed that diode properties change with increasing deposition pressure.

Unveiling the Semiconducting Diode Property through Current Density–Voltage Features with Effective Interface Mobility and Conductivity of Nitroterephthalic Acid-Directed Supramolecular Co(II)/Cu(II) Metallogels

Unveiling the Semiconducting Diode Property through Current Density–Voltage Features with Effective Interface Mobility and Conductivity of Nitroterephthalic Acid-Directed Supramolecular Co(II)/Cu(II) Metallogels

Impact of rectifier metal-semiconductor contact geometry on electrical properties of Schottky diodes with Mg3N2 interfacial layer

The Ag/Mg3N2/p-Si heterojunction diode (HD) with rectifier contacts (RCs) with the same area in various geometries were fabricated through thermal evaporation, and the electrical performances of these diodes was compared. The geometry of the RC was found to affect various electrical properties such as ideality factor, saturation current and barrier height of HD, the rectifier rate, and the leakage current of the diodes. The experimental demonstrated the HD with a circular RC exhibited a higher rectifying ratio and lower leakage current compared to the other RCs. Hence, the design and optimization of the RC play a critical role in achieving the desired electrical properties of diode. These diodes, featuring an Mg3N2 interfacial layer and showcasing photoconductive behavior, can be utilized as photodiodes in various optoelectronic devices.

Diode paremeters extraction and study of space charge limited current in (Ag, Au)/CoS2 Schottky diodes

We investigated the electron transport properties of cobalt sulphide Schottky diodes with Au and Ag metal contacts. Pure CoS2 nanoplates were synthesized using solid state reaction method. From temperature dependent IV characterstics diode parameters including ideality factor, barrier height and Richardson cofficient were calculated for Au/CoS2 and Ag/CoS2 diodes. The value of barrier height increased with increasing temperature for both devices, however Ideality factor showed different trend. The values of modified Richardson coefficient by assuming the Gaussian distribution of the barrier heights turns out to be 244.20Acm−2K−2 and 348.20Acm−2K−2 for Au/CoS2 and Ag/CoS2 diodes respectively. At high voltages we observed Space Charge Limited Current (SCLC) with an exponential trap distribution in Au/CoS2 diode. The density of the traps and characteristic temperature associated with these traps were determine to be 2.47×1014cm−3 and 141 K, respectively.

Triple-layer remote phosphor geometry: an excellent selection to improve the optical properties of white light-emitted diodes

High performance white-light-emitting diodes (WLEDs) have been the goal of recent research on phosphor-in-glass (PiG) devices. In this paper, we introduce a configuration of WLED that achieves high color rendering index (CRI), and correlated color temperature with the addition of Zn<sub>2</sub>SiO<sub>4</sub>:Mn<sup>2+</sup>, As<sup>5+</sup> and YAl<sub>3</sub>O<sub>4</sub>B<sub>12</sub>:Eu<sup>3+</sup><sub>. </sub>The technique is lower the temperature during the creation process of phosphor in glass and control the consistent thickness in between 0.5 to 0.7 mm to yield high color quality PiG, high CRI above 80 WLEDs, and extend the color temperature range to 3,900 to 5,300 K. The consistent heat generation combined with extraordinary CRI for PiG prove that low temperature sintering has the potential to create WLEDs with advanced quality. The improved WLEDs can be utilized in many high-demand lighting fields such as chromatic examination, medical analysis, and aesthetic lighting.

Exploration of microstructural, chemical states and electrical features of the Au/Er2O3/n-GaN MIS diode with a Er2O3 interlayer

The study involved the formation of high-k erbium oxide (Er2O3) films on the n-GaN surface and evaluated their microstructural and chemical states by XRD, TEM and XPS approaches. By employing Er2O3 as an interlayer between the Au and n-GaN substrate, the metal/insulator/ semiconductor (MIS) diode is developed and explored its electrical features by I–V and C–V procedures. The electrical properties of the MIS diode demonstrate a better rectification nature with a lower leakage current compared with the Au/n-GaN Schottky diode (SD). The MIS diode's derived barrier height (BH) is higher than the SD, suggesting that Er2O3 plays a momentous role in altering the BH. The BH was determined using Cheung’s and Norde techniques, and the measurements showed a high degree of consistency, indicating the methods used are valid. The derived density of states (NSS) value for the MIS diode is beneath the SD, suggesting that the Er2O3 layer significantly contributes to the reduction of NSS. Under reverse bias, the PFE is a dominant current mechanism in the lower-bias, whereas the SE is the leading current mechanism in the higher-bias region of the SD. However, the PFE is the prevailing conduction mechanism in the lower-bias and higher-bias regions of the MIS diode. Outcomes of the investigation reveal that the Er2O3 thin films are favorable interfacial layers for fabricating MIS/MOS diodes.

Opto-electronic transport properties of resonant tunneling diodes with type-I and II postwells

We investigate the opto-electronic transport properties of AlGaAs/GaAs double-barrier resonant tunneling diodes (RTDs) with GaAs1−xSbx type-II postwells and compare these to RTDs with InxGa1−xAs type-I postwells. Samples grown with Sb containing type-II postwells show a significant photocurrent enhancement for x = 24% compared to 5.5% and 34%, respectively, which is attributed to an efficient hole trapping based on the large hole trapping barrier of 396 meV. By contrasting the RTDs with type-I InGaAs quantum well RTDs, we observe an increased photoresponsivity by one order of magnitude. Our finding allows realizing RTD with efficient hole trapping in the vicinity of the active region of the double barrier structure with confinement energies well above the thermal energy at room temperature, which may allow the observation of single charge configurations even at elevated temperatures.

Modular Optical Diodes for Circular Polarization Based on Glass‐Supported Cellulose Nanocrystal/Polyethylene Glycol Composite Films

Depending on processing methods and conditions, cellulose nanocrystal (CNC) films exhibit linear birefringence or selective Bragg reflection. The latter means reflection of light with left‐handed circular polarization (LCP) due to CNC in a helicoidal microstructure of the same handedness. Herein, glass‐supported CNC/polyethylene glycol (CNC/PEG) composite films with PEG concentrations in the range of 0–30% w/w with selective Bragg reflection at wavelengths from 440 to 550 nm are prepared. A modular device comprised of a dip‐coated birefringent CNC‐glass sample sandwiched between two CNC/PEG‐glass samples shows different responses to light with LCP and to light with right‐handed circular polarization (RCP). The device suppresses selective Bragg reflection from the rear (front) CNC/PEG sample for incident light with LCP (RCP), even when the birefringent film does not meet the condition for a halfwave plate. This behavior resembles the performance of optical diodes for circular polarization. Polarization properties of composite films and optical diodes in terms of degree of polarization and ellipticity are discussed within the Stokes–Mueller formalism. Electromagnetic simulations of Mueller matrices reveal the equivalence of modular and in‐tandem film approaches of optical diodes.

Determining the Role of Oxygen in Obtaining Long-Term Stable Superhydrophilic Surfaces on Metals Treated with a Femtosecond Laser.

Laser processing is a simple way to obtain hydrophobic or even superhydrophobic properties of metal surfaces. However, preparation of superhydrophilic surfaces by this method, the properties of which do not change under the influence of various factors, remains a difficult task. In this work, we show that with increasing laser power, the degree of oxidation of the treated metal surface also increases. As a result, highly oxidized samples showed highly stable superhydrophilic properties. A Janus membrane fabricated from a stainless steel mesh with asymmetric hydrophilic-hydrophobic wettability demonstrated stable water diode properties. In addition, it was found that during the examination of sample surfaces by Raman spectroscopy, organic compounds adsorbed on the hydrophobic surface were decomposed by the laser of the spectrometer, which imposes limitations on the laser power when using this method in characterizing hydrophobic surfaces of metals fabricated by laser processing.

Electrical Properties of Anisotype ZnO:Al/n-ZnSe/p-CdTe Heterostructures.

ZnO:Al/n-ZnSe/p-CdTe anisotype heterostructures with diode properties were fabricated by the high-frequency magnetron deposition of ZnO:Al and n-ZnSe thin films onto the surface of crystalline p-CdTe. The flow of currents limited by the space charge at forward voltages up to 0.45 V and tunneling currents at V > 0.45 V was established. A change in these current flow mechanisms was observed at reverse voltages V = -0.6 V. The main part of the energy barrier qϕk = 1 eV of the ZnO:Al/n-ZnSe/p-CdTe heterostructure was formed in the p-CdTe substrate, which was established from studies of capacitance-voltage (C-V) characteristics. A model of the energy diagram of the heterostructure is proposed.

Chaotic-cavity surface-emitting lasers for optical wireless communication and low-speckle illumination

Though necessary and advantageous in many fields, the high coherence of lasers is detrimental to their performance in certain applications, including illumination, imaging, and projection. This is due to the formation of coherence artifacts, commonly known as speckles, resulting from the interference of randomly scattering spatially coherent photons. It is possible to resolve this issue by increasing the number of mutually incoherent modes emitted from the laser. In vertical-cavity surface-emitting lasers (VCSELs), this can be performed by designing them to have chaotic cavities. This paves the way toward their use in simultaneous illumination and communication scenarios. Herein, we show that chaotic-cavity broad-area VCSELs can achieve significantly broader modulation bandwidths (up to 5 GHz) and higher data rates (up to 12.6 GB/s) compared to other low-coherence light sources, with a lower speckle contrast. We further report a novel technique for lowering the speckle contrast by carefully designing the AC signal used for communication. We show that the apparent spatial coherence is dramatically decreased by inserting a short chirp signal between symbols. Using this method with a chaotic-cavity VCSEL, the number of apparent modes can be up to 450, compared to 88 modes measured from a conventional broad-area VCSEL (a fivefold increase). In light of the recent advances in visible-light VCSELs, this work shows the potential of low-coherence surface-emitting lasers (LCSELs) in simultaneous illumination and optical wireless communication systems since they combine the high speed of lasers with the excellent illumination properties of light-emitting diodes.

Simultaneously improved hole injection and current uniformity in 293 nm AlGaN-based deep ultraviolet light-emitting diodes

Insufficient hole injection and current nonuniformity caused by the nature of the p-AlGaN hole injection layer (HIL) are two issues impeding the advances in the optical and electrical properties of AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs). To simultaneously improve the hole injection efficiency and current uniformity, an Al-linearly-decreasing AlGaN PN junction (ALD AlGaN PN junction) is proposed to replace the conventional p-AlGaN HIL with a constant Al component. The barrier height for holes at the interface between the p-type electron blocking layer (p-EBL) and HIL as well as the hole concentration and resistance in the p-AlGaN HIL can be modulated at the same time by the proposed ALD AlGaN PN junction. As a result, the hole injection efficiency is enhanced due to the reduced barrier height at the p-EBL/HIL interface and the polarization-induced three-dimensional hole gas (3DHG) induced in the proposed ALD AlGaN PN junction HIL. In addition, the lateral current uniformity is improved by the properly regulated resistance in the p-AlGaN HIL, which can be ascribed to the additional barrier for holes in the valence band because of the incorporated ALD AlGaN PN junction. The proposed DUV LED with ALD AlGaN PN junction exhibits enhanced EQE by a factor of 39.2% at 100 A/cm2 and simultaneously improved current uniformity in the active region. This designed ALD AlGaN PN junction structure provides a promising strategy for achieving high-performance DUV LEDs.

A first-principles study of B/N doping on the transport properties of ultrafine single-walled carbon nanotubes

As the size of carbon nanotube (CNT)-based devices continues to shrink, the demand for the development of a new kind of miniature nanodevice is starting to be on the agenda. In single-walled carbon nanotubes (SWCNTs) of different sizes, B and N atoms are doped into the electrodes and central scattering region in different patterns to create a nanoscale junction with rectification properties. With a width of 0.6 nm and a length of 3.4 nm, this junction channel has a footprint of 5.1 nm. We found that this nano-junction has the properties of an ideal diode. With the 0.4 V bias, the junction emits a leakage current of 2.5 × 10−6 µA, a rectifying ratio of 7.96 × 104, which is far greater than the high-performance transistor device built on semiconductor CNT arrays under a 0.4 V bias. To further analyze the effect of device size and doping lattice sites on the transport characteristics, we have analyzed how the concentration and distribution of different dopants in nanoscale CNTs of different lengths affect the I-V curves of CNTs so that later studies can select the appropriate doping structure as needed.

Schottky barrier heights and electronic transport in Ga2O3 Schottky diodes

The Schottky contact, formed at the interface between a metal and a semiconductor, is instrumental in defining the electrical properties of Schottky barrier diodes (SBDs). The characteristics of the Schottky contact are contingent on the properties of interacting metal and semiconductor properties. Herein, we studied the carrier-transport mechanisms and electrical characteristics at room and elevated temperatures. These SBDs employ pre-treated Ga2O3 thin films and either Ni or Au Schottky contacts. The SBDs pre-treated (pre-T) via annealing at 900 °C under an N2 atmosphere for the Ni contact showed highest on/off ratio at room temperature. They also demonstrated ideality factors and Schottky barrier heights (SBHs) that remained relatively stable between 298 K and 523 K. To ascertain the SBH, ideality factors (n) derived from the thermionic emission (TE) and thermionic field emission (TFE) models were used, and results were subsequently compared. Moreover, SBDs employing Ni as the anode material exhibited lower SBHs than those employing Au. The pre-T Ni SBD was best described by the TFE model, wherein the SBH and ideality factor varied by 0.14 eV and 0.13, respectively, between 298 K and 523 K. Conversely, for pre-T Au, untreated Ni, and untreated Au SBDs, neither TE and TFE provided a satisfactory fit due to the ideality factor is greater than 2 at room temperature and the variation of SBH and n with temperature. These suggests that the transport mechanism should be described by other physical mechanisms. Without pre-treatment, both the Ni and Au SBDs exhibited more significant variation in the SBH and n with temperature. SBHs values were determined using measurement of current, capacitance and x-ray photoelectron spectroscopy, and were found to depend on the interface quality, indicating inhomogeneous SBH. Our results suggest that the use of annealing pre-treatments and anode metals with low work functions holds considerable potential for reducing Schottky barrier heights in Schottky diodes, thereby enhancing their electrical performance.

Effect of phosphoric acid chemical etching on morphological, structural, electrical, and optical properties of porous GaAs Schottky diodes

Effect of phosphoric acid chemical etching on morphological, structural, electrical, and optical properties of porous GaAs Schottky diodes

Chemical Reactivities and Organic Light-emitting Diode Properties of some Polyaromatic Molecules

High-performance organic-light emitting diode (OLED) display panels have been very popular lately due to their many advantages compared to liquid-crystal display (LCD) and light-emitting diode (LED) panels. It is also well known that the materials used in OLED panels are important in determining OLED performance. Starting with the selection of materials which have rich π-electrons will be a good start for the design of high-performance OLED materials. For this aim, the OLED properties of some cyclic aromatic structures with rich π-electrons such as 2,2ꞌ-bi-1,6-naphthyridine (BNP), 1,6-bis(4ꞌ-pyridine)-2,5-diazahexane (BPDH), 3,3ꞌ-bis[3-(2-pyridyl)pyrazol-1-yl]biphenyl (BPPB), 5,5ꞌ-dicyano-2,2ꞌ-bipyridine (DCBP), 2,2ꞌ-dimethyl-4,4ꞌ-bipyrimidine (DMBP), and 4ꞌ-phenyl-2,2ꞌ:6ꞌ2ꞌꞌterpyridine (Ph-TERPY) were theoretically analyzed using computational chemistry tools. The calculations of monomeric and dimeric structures of mentioned molecules were carried out at B3LYP/6-31G(d) and B3LYP/TZP levels, respectively. The OLED properties of the investigated compound were explained by means of OLED parameters such as the reorganization energies, adiabatic-vertical ionization potentials and adiabatic-vertical electron affinities, the effective transfer integrals, and the charge transfer ratios. In the light of computational chemistry, it is indicated that these studied molecules will be utilized in which layers of OLED device. In addition to OLED analysis, in the light of the calculated reactivity descriptors, the chemical reactivities of the studied molecules were discussed.

Performance prediction of current-voltage characteristics of Schottky diodes at low temperatures using artificial intelligence

Schottky diodes are still one of the most important elements of electronics. Therefore, investigating the properties of diodes is very important in determining their usage areas. In this study, the performance of the artificial neural network model trained using high temperature data in predicting the current-voltage properties at low temperatures was investigated. An artificial neural network is modeled using the experimentally measured current and voltage values at the temperature range of 80 and 375 K. In the developed network model, temperature and voltage values are defined as input parameters and current values are estimated. Levenberg-Marquardt training algorithm was used as the training algorithm in the neural network, which was developed using a total of 1584 data. The current values obtained from the artificial neural network were compared with the experimental current values, and the prediction performance of the network model was extensively analyzed by using various performance parameters. The results showed that the developed artificial neural network can predict current values at low temperatures with high accuracy depending on voltage. In addition, it was found that the current-voltage characteristics of the Schottky diode at low temperatures could be predicted with an error rate of approximately ±7 %. On the other hand, the error rates in the prediction of diode characteristics by artificial intelligence were determined to be independent of temperature.

Field and temperature tuning of magnetic diode in permalloy honeycomb lattice

The observation of magnetic diode behavior with ultra-low forward voltage renders new venue for energetically efficient spintronic device research in the unconventional system of two-dimensional permalloy honeycomb lattice. However, detailed understanding of temperature and magnetic field tuning of diode behaviors are imperative to any practical application. In this report, our study unveils many important properties of magnetic diode that not only pave the way for practical applications, but also underlines the role of emergent phenomena of magnetic charge correlation on honeycomb vertices. We find that magnetic diode behavior persists across a broad temperature range. In a surprising observation, magnetic field application tends to induce a peculiar reentrant characteristic where diode behavior is suppressed in remnant field but reappears after warming to room temperature. Analysis of $I-V$ data suggests a modest energy gap, $∖sim$ 0.03 - 0.1 eV, which is comparable to magnetic Coulomb’s interaction energy between emergent magnetic charges on honeycomb vertices in the reverse biased state. It affirms the role of magnetic charge correlation in unidirectional conduction in 2D honeycomb lattice. The experimental results are expected to spur the utilization of magnetic diode in next generation spintronic device applications.