Diode Behavior Research Articles

Monte Carlo Simulation of Electron Beam Induced Current in Au/Si Schottky Diodes: effects of metal layer thickness and minority carrier diffusion length

The Electron Beam Induced Current (EBIC) technique, when combined with scanning electron microscopy (SEM), offers valuable insights into the electronic properties of semiconductor materials at the nanoscale. This study leverages EBIC and Monte Carlo simulations to investigate the behavior of Schottky diodes, particularly focusing on the influence of gold layer thickness on current gain and backscatter electron (BSE) yield. The simulation results reveal the significant effects of depletion depth and minority carrier diffusion length on the diode’s performance. A key finding is that the EBIC current decreases with increased gold layer thickness, due to a higher BSE fraction. Additionally, at low beam energies, the current is negligible when the interaction volume is confined within the metal layer, while at higher energies, some penetration into the semiconductor occurs, generating a measurable EBIC current. These findings provide a better understanding of the interplay between metal layer thickness and semiconductor performance, which is crucial for optimizing semiconductor devices.

Optical and electrical degradation behavior of GaN-based UV-A laser diodes

The degradation mechanism of GaN-based ultraviolet (UV-A) laser diodes (LDs) is analyzed by studying the changes of their electrical and optical properties after aging process with the operation current below the threshold current (Ith). After aging treatment, Ith increases, the slope efficiency decreases, and the leakage current increases. In particular, the emission spectra of aged LD show significant broadening, with additional peaks on the shorter wavelength side. Both cathodoluminescence and deep level transient spectrum results indicate defects can develop around the active region of the LD, even when the operation current is below Ith. This leads to an increase in trap-assisted tunneling current and non-radiative recombination. The observed defects may result from the diffusion of water molecule in the environment from the cavity facet into the active region and formation of ON–CN and VGaON complex defects. These defects not only reduce the effective carrier concentration injected into the quantum well but also increase non-radiative recombination. These results will contribute to our understanding of the degradation mechanism of UV LDs and the preparation of long lifetime UV LDs.

Zn(II)-based mechanically flexible metallosupramolecular network: Investigating rheology, morphology, anti-bacterial effect and semiconducting device performances

Synthesis of supramolecular Zn(II)-metallogel of succinic acid with N,N′-dimethyl formamide (DMF) solvent has been explored in this present study. Succinic acid is used as a low molecular weight gelator (LMWG) and DMF acts as a metallogel-immobilized solvent-media. Mechanical flexibility, viscous, and elastic behaviours of the metallogel are characterized by exhaustive rheological experiments. Different rheological parameters like storage modulus (G′) and loss modulus (G″) are evaluated for certain regions of shear strain and angular frequency. The morphological decoration of xerogel material obtained from Zn(II)-based metallosupramolecular gel (i.e., Zn-Succinic) has been visualized through field emission scanning electron microscope (FESEM). Energy dispersive X-ray analysis (EDX) verifies the active involvement of metallogel-forming chemical constituents. The flexible metallosupramolecular scaffold-construction strategy has been unveiled through infrared spectroscopic data and ESI-Mass investigations. The antibacterial potency of Zn(II)-directed metallogel has also been verified against several Gram-positive bacteria (i.e., Bacillus cereus (ATCC 13061), Bacillus subtilis (MTCC 121), Listeria monocytogenes (MTCC 657), Staphylococcus aureus (MTCC 96)), and two Gram-negative bacterial strains (i.e., Salmonella typhimurium (MTCC 98) and Escherichia coli (MTCC 1667)). Even, Zn-Succinic metallogel exhibits Schottky diode behaviour with a significant non-linear rectifying nature in I-V curve, proving the semiconducting diode features with electrical parameters.

The Chaotic Behavior of an Optical Artificial Neuron

ABSTRACT The operation of an optical neural network via a feed-forward (FF) configuration is experimentally simulated in the laboratory. The FF setup is tested using optical injection (OI), and the behavior of follower laser diodes (FLDs) subjected to chaotic modulation is examined. The last two laser diodes (LDs) are exposed to different weights of chaotic modulated signals through optical filtration and attenuation. Observations of the emissions from these two FLDs during FF operation are verified by frequency spectra calculated from time-series data. Signal broadening is assessed by measuring the full width at half maximum (FWHM), and chaotic signal spikes are analyzed by counting the number of peaks associated with signal amplitudes for the FLDs. Additionally, LD control parameters, including the bias voltage of the influencer laser diodes (ILD1, ILD2) and two additional FLDs, are examined. A maximum FWHM of 1.25 GHz for FLD2 is observed with a bias voltage of 3.6 V and a modulated signal attenuation of −12 dB. To determine the synchronization state, the correlation between the ILDs and FLDs is calculated. Results indicate fluctuations between negative and positive values, with the best correlation value being 0.4. These results confirm anti-synchronized ILD-FLDs, which are crucial for ensuring privacy in transmitting units within a chaotic optical communication system simulating an optical neural network.

Tracing the electron transport behavior in quantum-dot light-emitting diodes via single photon counting technique

The electron injection and transport behavior are of vital importance to the performance of quantum-dot light-emitting diodes. By simultaneously measuring the electroluminescence-photoluminescence of the quantum-dot light-emitting diodes, we identify the presence of leakage electrons which leads to the discrepancy of the electroluminescence and the photoluminescence roll-off. To trace the transport paths of the leakage electrons, a single photon counting technique is developed. This technique enables us to detect the weak photon signals and thus provides a means to visualize the electron transport paths at different voltages. The results show that, the electrons, except those recombining within the quantum-dots, leak to the hole transport layer or recombine at the hole transport layer/quantum-dot interface, thus leading to the reduction of efficiency. By reducing the amount of leakage electrons, quantum-dot light-emitting diode with an internal power conversion efficiency of over 98% can be achieved.

Organic Heterostructures with Dendrimer Based Mixed Layer for Electronic Applications.

Recently, much research has focused on the search for new mixed donor-acceptor layers for applications in organic electronics. Organic heterostructures with layers based on the generation 1 poly(propylene thiophenoimine) (G1PPT) dendrimer, N,N'-diisopropylnaphthalene diimide (MNDI), and a combination of the two were prepared and their electrical properties were investigated. Single layers of G1PPT and MNDI and a mixed layer (G1PPT:MNDI) were obtained via spin coating on quartz glass, silicon, and glass/ITO substrates, using chloroform as a solvent. The absorption mechanism was investigated, the degree of disorder was estimated, and the emission properties of the layers were highlighted using spectroscopic methods (UV-Vis transmission and photoluminescence). The effects of the concentration and surface topographical particularities on the properties of the layers were analyzed via atomic force microscopy. All of the heterostructures realized with ITO and Au electrodes showed good conduction, with currents of the order of mA. Additionally, the heterostructure with a mixed layer exhibited asymmetry in the current-voltage curve between forward and reverse polarization in the lower range of the applied voltages, which was more significant at increased concentrations and could be correlated with rectifier diode behavior. Consequently, the mixed-layer generation 1 poly(propylene thiophenoimine) dendrimer with N,N'-diisopropylnaphthalene diimide can be considered promising for electronic applications.

Investigation of the performance and stability of self-powered polythiophene-based photodiodes under UV and visible light illumination

In this study, we fabricated polythiophene (PTh) and silver-decorated polythiophene (Ag@PTh) films on n-type silicon substrates using the electrochemical deposition method to investigate their electrical and photoelectrical properties in metal/interlayer/n-Si heterostructures under various conditions. The physical properties of the films were comprehensively investigated through UV-Vis, Raman, XPS and SEM analysis. The results from these analyses confirmed the successful deposition and formation of the films on the n-Si substrates. Additionally, a comparison of the current-voltage (I-V) characteristics of the PTh/n-Si and Ag@PTh/n-Si devices was conducted under both dark conditions and illumination with visible and UV light. While both devices exhibited typical rectifying diode behavior, the Ag@PTh/n-Si device demonstrated greater rectification with a RR of 2.49 x 105 at ± 2 V under dark conditions. In addition, the Ag@PTh/n-Si device, with self-powered property, displayed notably enhanced performance metrics, including a significantly higher ON/OFF ratio, responsivity, and detectivity, particularly evident under UV light illumination when compared to white light. Furthermore, to assess the long-term reliability of these devices, stability tests were conducted by repeating the I-V measurements after 90 days under identical conditions. The Ag@PTh/n-Si device exhibited considerably better stability over time than the PTh/n-Si device, maintaining consistent performance without notable degradation. So, in light of the findings, it can be concluded that the Ag@PTh/n-Si device has substantial potential for advancing optoelectronic technology.

Anomalous Electrical Behavior of 4H-SiC Schottky Diodes in Presence of Stacking Faults

In this work, we investigated the impact of crystallographic defects (specifically stacking faults, SFs) on the mechanisms of the current transport in 4H-SiC Schottky contacts. The electrical characteristics were studied under both forward and reverse bias. In particular, while the presence of SFs under the contact did not show a significant impact on the forward characteristics of the Schottky diode, a significant increase in the leakage current occurred under reverse bias in defective diodes. This anomalous behavior can be explained by a space-charge limited current model, consistent with the presence of a trapping state distribution in the 4H-SiC gap. An increase of the reverse bias above 30 V leads to a complete trap filling. The weak temperature-dependence of the leakage current observed at highest voltage suggests that a tunneling of the carriers through the barrier can be also present.

A Geometry-Scalable Physically-Based SPICE Compact Model for SiC MPS Diodes Including the Snapback Mechanism

In this paper, a simple compact model for the static behavior of SiC MPS diodes is developed in the form of a SPICE-compatible subcircuit. The model is suited to describe the undesired snapback mechanism likely to occur in unoptimized high-voltage MPS structures with narrow width of the PiN portion and/or very thick drift layer; in particular, the model accounts for the snapback mechanism both as the cell extension varies and as individual portions of Schottky and PiN vary. Sentaurus TCAD simulations of a 10-kV MPS diode are used as a reference for the calibration of the model parameters and accuracy verification.

Investigation of the mechanism of carrier recombination in GaN-based blue laser diodes before lasing

Abstract The carrier recombination behavior of GaN-based blue laser diodes (LDs) is studied and analyzed by experiments and simulation calculations before lasing, with a particular focus on the role of Auger recombination. It is found that Auger recombination plays a crucial role in the decrease in differential efficiency and threshold current of GaN-based blue LDs. The theoretical calculation results show that a large Auger recombination rate may lead to a dominant recombination channel before lasing, which could exceed the radiation recombination and result in an obvious decrease in the differential efficiency. Such a high Auger recombination will dissipate a large number of carriers in the quantum well, resulting in deterioration of device performance, a higher threshold current and a lower efficiency. This work presents a method to evaluate Auger recombination through differential efficiency and also provides evidence that suppressing the Auger recombination rate is beneficial to improve the performance of blue LDs.

Modeling and Analysis of Shutdown Dynamics in Flying Capacitor Multilevel Converters

This work explores the dynamic behavior of the flying capacitor multilevel (FCML) converter during unplanned shutdown. A model for a general N-level FCML converter is developed, which captures capacitor non-linearities, component leakage paths, and body diode behavior. This work highlights how switch voltage ratings may be exceeded during unplanned shutdown, and proposes several mitigation strategies. Using a ten-level FCML converter hardware prototype, the time-domain behavior of the model is verified, and a successful hardware mitigation strategy is demonstrated which ensures safe and rapid converter shutdown.

Cu2O/TiO2 core–shell nanowire heterojunction for high-performance self-powered photodetector

High-performance self-powered photodetectors (PDs) have great commercial value in optical communication, intelligent sensing and medical diagnosis. However, the limited active area of traditional thin film heterojunction seriously restricts the photoelectric performance of the detector. In this paper, the Cu2O/TiO2 core-shell nanowire (NW) heterojunction PD was synthesized for the first time by simple hydrothermal and electrochemical deposition methods, which effectively improved the response performance and response speed of the device based on its broad photoactive area and ordered carrier transport path. The PD exhibits significant diode behavior, with rectification ratios of 543 at ±2 V. The responsivity is as high as 6.8 mA W−1 at zero bias under 490 nm illumination. The short rise and decay times measured are 0.09 and 0.18 s at zero bias, respectively. Obviously, this low-cost, high-performance self-powered Cu2O/TiO2 core-shell NW heterojunction PD shows great promise in future optoelectronic device applications.

Quaternary functional semiconductor devices

Al/(Zn:Cd:Ni:TiO2)/p-Si diodes with (4:2:2:2), (5:2:2:1) and (6:4:4:0) ratios were named as D1, D2, D3, and Al/(CdO:ZnO:NiO:Ti)/p-Si diodes with of (4:2:2:2), (5:2:2:1) and (6:4:4:0) ratios were named as D4, D5 and D6, respectively. The functional interlayer was deposited via sol-gel spin coating method to develop new diodes/structures. Whereas the Ln(I)–V plot shows two linear sections for D1, D2, D3, and D5 structures, D2 and D6 revealed only one linear section in the forward-bias voltages. Therefore, D1, D2, D3, and D5 structures were found to exhibit two-exponential or two-parallel diode behavior in literature. The main electric parameters such as zero-bias barrier height, BH, (Φbo), ideality factor (n), reverse saturation-current (Is or Io)), rectification ratio at ±4.5 V, series resistance (Rs) and shunt resistance (Rsh) were extracted from the current-voltage (I-V) measurements. The number of surface sates (Nss) and their energy distribution were obtained using forward-bias I-V data by considering the voltage dependence of n and Φbo for each diode. The capacitance/conductance-voltage (C/G–V) plots at 1 MHz were used for extracting some of the other basic electrical parameters. The comparison of all the experimental results suggests that D1 and D3 structures have good performance in terms of lower leakage current, Nss and higher RR and so could be successfully used instead of conventional metal/insulator/semiconductor (MIS) structures.

A coarse-grained Poisson–Nernst–Planck model for polyelectrolyte-modified nanofluidic diodes

Abstract Polyelectrolyte (PE)-modified synthetic nanopores have gained substantial research attention because molecular modification promotes ion gating and rectification. However, theoretical research on PE-modified nanopores is relatively scarce because it is difficult to establish an elaborate model for PEs, and it accordingly causes a trade-off between the computational resources needed and the accuracy. Therefore, an appropriate simulation method for the PE-modified nanopore is in high demand and still an enormous challenge. Herein, we report the simulation result of ion transport through PE-modified nanopores through a coarse-grained Poisson–Nernst–Planck method. By modeling the stuffed PE molecules as PE particles in a well-established continuum model, adequate computational accuracy can be achieved with acceptable computational cost. Based on this model, we study the ion transport in PE-modified nanofluidic diodes and reveal the PE around ion selectivity, which can explain the previous experimental works. Intriguingly, we found that the ion enrichment state in the nanofluidic diode is sensitive to steric hindrance and charge distribution near the heterojunction region. This property is critical for the ion transport behavior in the PE-modified nanofluidic diodes. Based on this property, we predict a heterogeneous structure that can realize the single molecule response to charged analytes. These findings provide insights for understanding the ion transport in PE-modified nanofluidic systems and bring inspiration to the design and optimization of high-performance chemical sensors.

Embellished photosensitive Schottky barrier diode functionality of Ni(II)/Pb(II)-Salen complex with SCN− spacers: Insights from experimental and theoretical rationalization

This research article explores the synthesizing, structural characterizing, and photosensitive Schottky diode behaviour (PSBD) of one new hetero-nuclear Ni(II)/Pb(II)-Salen complex, [Ni2(L)Pb(μ-1,3-SCN)2(H2O)]2. The complex utilizes various analytical methods for characterization purposes, including single-crystal X-ray diffraction (SCXRD). Crystals have formed in the monoclinic space group P21/n within the compound. The complex asymmetric unit contains a deprotonated ligand (L2−), two Ni(II), one Pb(II), two SCN− ions, and Ni(II) metal coordination by H2O molecule. The crystallographic structure has octahedral and see-saw geometries around the Ni(II) and Pb(II) metal ions. The crystal structure reveals remarkable supramolecular interactions, with significant S⋯H contacts (13 %) evident from the Hirshfeld surface (HS) and 2-D fingerprint plots. The calculated optical band gap (3.14 eV) and UV–Visible measurement support the semiconductor behaviour. In addition, the compound shows electrical conductivity and photosensitivity (dark & light), suggesting potential applications in optoelectronic devices. The complex transports charge through space via a hopping process. The extensive experimental investigations indicate that exposure to visible light increases electrical conductivity compared to dark conditions, popularly known as PSBD behaviour. The complex conductivity function substantiates the DFT-based DOS, PDOS, and OPDOS plot analysis. Therefore, the heteronuclear complex has been successfully used in thin-film active devices despite technological challenges.

An Expansion of Polarization Control Using Semiconductor-Liquid Junctions.

This report examines the concept of independent control over current and applied potential in electrocatalysis, as a means of improving control over product selectivity. Previous work, while permitting separate modulation of current and potentiostat bias, precluded independent control over the current flow and applied cell potential. This study seeks to resolve that limitation by exploiting the Schottky diode behavior inherent to semiconductor-electrolyte interfaces. Light is explored as a prospective second degree of freedom for controlling polarization in a suitably designed, photoelectrochemical (PEC) device, enabling the arbitrary selection of current with respect to an applied cell potential. In contrast to metal electrodes, the property of light-dependent carrier concentrations in semiconductors forms the operative means of controlling charge fluxes at some arbitrary applied potential in PEC devices featuring a semiconductor-liquid junction. This functionality enables exploration of polarization states distinct from those accessible with a dark cell, with implications for improved control over electrochemical reactions.

Lateral Heterometal Junction Rectifier Fabricated by Sequential Transmetallation of Coordination Nanosheet.

Heterostructures of two-dimensional materials realise novel and enhanced physical phenomena, making them attractive research targets. Compared to inorganic materials, coordination nanosheets have virtually infinite combinations, leading to tunability of physical properties and are promising candidates for heterostructure fabrication. Although stacking of coordination materials into vertical heterostructures is widely reported, reports of lateral coordination material heterostructures are few. Here we show the successful fabrication of a seamless lateral heterojunction showing diode behaviour, by sequential and spatially limited immersion of a new metalladithiolene coordination nanosheet, Zn3 BHT, into aqueous Cu(II) and Fe(II) solutions. Upon immersion, the Zn centres in insulating Zn3 BHT are replaced by Cu or Fe ions, resulting in conductivity. The transmetallation is spatially confined, occurring only within the immersed area. We anticipate that our results will be a starting point towards exploring transmetallation of various two-dimensional materials to produce lateral heterojunctions, by providing a new and facile synthetic route.

Lateral Heterometal Junction Rectifier Fabricated by Sequential Transmetallation of Coordination Nanosheet**

AbstractHeterostructures of two‐dimensional materials realise novel and enhanced physical phenomena, making them attractive research targets. Compared to inorganic materials, coordination nanosheets have virtually infinite combinations, leading to tunability of physical properties and are promising candidates for heterostructure fabrication. Although stacking of coordination materials into vertical heterostructures is widely reported, reports of lateral coordination material heterostructures are few. Here we show the successful fabrication of a seamless lateral heterojunction showing diode behaviour, by sequential and spatially limited immersion of a new metalladithiolene coordination nanosheet, Zn3BHT, into aqueous Cu(II) and Fe(II) solutions. Upon immersion, the Zn centres in insulating Zn3BHT are replaced by Cu or Fe ions, resulting in conductivity. The transmetallation is spatially confined, occurring only within the immersed area. We anticipate that our results will be a starting point towards exploring transmetallation of various two‐dimensional materials to produce lateral heterojunctions, by providing a new and facile synthetic route.

Tribotronic Vertical Field‐Effect Transistor Based on van der Waals Heterostructures

AbstractGraphene has attracted considerable interest for next‐generation electronics. However, the absence of natural bandgap has limited the current on/off ratio of graphene‐based transistors. Vertical integration of 2D heterostructures offers a promising approach to address this challenge, enabling high‐current‐density vertical field‐effect transistor (VFET) with large on/off ratio. Here, a triboelectric potential‐powered VFET with a vertical stacked graphene/MoS2 heterostructure and a sliding‐mode triboelectric nanogenerator (TENG) coupled with gate dielectrics are proposed. The tribotronic VFET has an ultrashort channel length in vertical direction, exhibiting excellent current driving capability with an ultrahigh on‐state current density of 950 A cm−2 and a good current on/off ratio of 630. It also demonstrates reconfigurable diode behavior with a rectification ratio over 102. Temperature‐dependent studies are applied to tribotronic devices for the first time, indicating an effective modulation on the Schottky barrier height of 150 meV by the triboelectric potential. A green LED pixel is driven by the tribotronic VFET as a demonstration to work as a tactile interactive light‐emitting device. The demonstrated tribotronic vertical device offers a promising strategy for integrating various 2D layered materials with TENG in vertical direction, enabling 3D integration of low‐power and interactive devices for next‐generation electronics.

Engineering of Molecular Bridge on Buried Interface via Ferrocene Carboxylic Acid for High Performance Perovskite Light‐Emitting Devices

AbstractQuasi‐two‐dimensional (Quasi2D) perovskite materials gained widespread attention due to whose unique and highly desirable luminescence properties. However, the behavior of perovskite lightemitting diodes (PeLEDs) is prejudiced by inefficient cascading energy transfer of perovskite film and unbalanced charges injection. Here, ferrocene carboxylic acid (FcAd) is employed between hole transport layer (HTL) and perovskite layer as a molecular bridge to solve the current problems of PeLEDs. Ferrocene units can bond with [PbBr6]4−, forming one‐dimensional (1D) intermediate phases of FcPbBr3 at the interface, which can manipulate the growth kinetics of perovskite and reconstruct the phase distribution. Therefore, due to the suppression of low dimensional phase content, not only is the cascaded energy transfer of PEA2(CsPbBr3)2PbBr4 films effectively achieved, but also the quasi‐2D perovskite's work function is reduced. Additionally, Pb2+ coordinated with the carboxyl group of FcAd, inducing an electric dipole effect that leads to an further upward shift of the perovskite energy level. Eventually, the synergy achieves a significant tailoring between the perovskite and HTL energy exhibits the most excellent external quantum efficiency (EQE) exceeds 27% and optimal brightness exceeds 240000 cd m−2. Therefore, the preparation method will provide an effective strategy to widen the color gamut of next‐generation displays.