Diode Behavior Research Articles

Prolonged Transient Behavior of Ultrathin Oxide MIS-Tunneling Diode Induced by Deep Depletion of Surrounded Coupling Electrode

In this article, the prolonged transient current and the coupled voltage retention behavior of ultrathin oxide MISTD induced by deep depletion of surrounded coupling electrode is investigated. The transient current is induced to balance the surrounded coupling electrode returning to its thermal equilibrium state, and the coupling voltage sensed is the result of the perturbation by the nearby deep depletion. The prolonged transient behavior of the sensed current is explained by the modulation of the hole leakage from the ring metal-insulator-semiconductor (MIS). Also, the behavior of the coupled voltage retention is the result of the generated electrons being swept toward the ring MIS by lateral field. The oxide thickness, coupling gap width, and trapping charges were shown to have influences on both behaviors. Moreover, the sensed coupled voltage of the center MISTD are utilized as memory characteristic and the operation of the proposed MIS memory cell is demonstrated. Oxide thickness smaller than 26 A was proposed for the prolonged transient phenomenon. The power consumption of this device is very low due to limited saturation current.

Synthesis and characterization of novel conjugated copolymers for application in third generation photovoltaic solar cells

An organic photovoltaic cell (OPV) is a subcategory of the third generation of photovoltaic cells. Advantages of OPV include lightness and ease of production in industrial scale. This work proposes the synthesis and characterization of two novel random and block copolymers for OPV containing fluorene (F), thiophene (T) and benzothidiazole (B) as structural units. Polymerizations were performed via the Suzuki-Miyaura mechanism. The yields obtained for both copolymers were around 65% with corresponding molar masses measured by GPC of 3394 and 4598 g/mol. From TGA, the onset degradation temperature was approximately 415 °C, while the maximum degradation temperature was around 440 °C, for both copolymers. FTIR and NMR analyses confirmed the ratio of aliphatic and aromatic carbons in the structure of both copolymers. Difference of chaining between both copolymers was verified by 13CNMR and XRD. The energy values of HOMO were -5.76 eV for random and -5.74 eV for block copolymer. Through UV-Vis spectroscopy, optical bandgaps of 2.39 and 2.34 eV were obtained for random and block polymers, respectively. Finally, LUMO energy levels of -3.37 eV (random) and -3.40 eV (block) were calculated by subtracting the optical band gap from the HOMO energy. Mobility measurements by JV method were performed in pure polymer films, rendering 1.91 × 10−6 and 1.35 × 10-8 cm2 /V.s for random and block copolymers, respectively. Copolymers were applied in conventional and inverted devices, presenting diode behavior. Energy efficiency obtained was higher for the block copolymer, which was consistent with the obtained interplanar distances estimated by XRD.

N-Buffer Design for Silicon-Based Power Diode Targeting High Dynamic Robustness and High Operating Temperature Over 448 K

In this article, we investigated the destructive behavior of the latest power diode when operating a hard-switching process. From the numerical simulation analysis, the destruction behavior originates in the enhanced impact ionization at the p-n junction on the anode side and current filament in the active region. A relaxing electric field on the anode side and a moderated electric field on the cathode side prevent the above-mentioned behavior. These improvements result from controlling the carrier-plasma layer in the n-buffer layer on the cathode side. This article demonstrates the effective n-buffer technology for the power diode that achieves superior dynamic robustness and high operating temperature over 448 K.

Current–voltage characterizations and photovoltaic properties of Se80Te15Ge5/p-Si heterojunction

Thin films of Se80Te15Ge5 were prepared by thermal evaporation technique onto a single-crystal p-Si substrate, and Au/Se80Te15Ge5/p-Si/Al heterojunction was obtained. The current–voltage characteristics of the junction in dark were evaluated in temperature range of 303–343 K and the voltage applied ranged from − 2 to + 2 V. It was found that the junction exhibits diode behavior with calculation for some diode parameters as rectification ratio, ideality factor(m), series resistance (Rs) and shunt resistance (Rsh). From the I–V characteristic curves of Au/Se80Te15Ge5/p-Si/Al, the operating mechanism was examined in both forward and reverse directions of the junction. The photovoltaic properties of the Au/Se80Te15Ge5/p-Si/Al under illumination of white light were investigated. The efficiency of the cell estimated and has a value of 3.68.

Fabrication and Characterization of Light Emitting Diode Based on n-ZnO Nanorods Grown Via a Low-Temperature

In this work, we report the fabrication of a near- ultraviolet (UV) light emitting (LED) device based on the growth of n-ZnO nanorod (NRs) arrays on the p-GaN layer/sapphire substrate heterostructure using the low-cost hydrothermal technique. Morphological, structural and optical properties of the as-fabricated sample are described. The room temperature current-voltage (I–V) measurements of the fabricated LED device confirmed a rectifying diode behaviour. The device presents near UV color under reverse bias. The luminescence properties of were investigated from both sides of the fabricated LED device at room temperature by electroluminescence (EL). EL spectrum of color emitting LED composed of intense peaks centered at 367 nm, 379 nm and a broad band around green emission. EL emission for the device has seen with the naked eye under normal light.

Thermal Analysis of Power Rectifiers in Steady-State Conditions

Power rectifiers from electrical traction systems, but not only, can be irreversibly damaged if the temperature of the semiconductor junction reaches high values to determine thermal runaway and melting. The paper proposes a mathematical model to calculate the junction and the case temperature in power diodes used in bridge rectifiers, which supplies an inductive-resistive load. The new thermal model may be used to investigate the thermal behavior of the power diodes in steady-state regime for various values of the tightening torque, direct current through the diode, airflow speed and load parameters (resistance and inductance). The obtained computed values were compared with 3D thermal simulation results and experimental tests. The calculated values are aligned with the simulation results and experimental data.

Exploring conduction mechanism and photoresponse in P-GaN/n-MoS2 heterojunction diode

Mixed-dimensional heterostructures have shown their potential in electronic devices. However, their functionality is limited by a complete understanding of the contacts and the current transport behavior. Here, we explore the electrical properties of the P-n heterojunction diode fabricated using p-type gallium nitride and layered molybdenum disulfide. The resulting P-n diode is rectifying in nature with current rectification of three orders of magnitude. The careful choice of Ohmic contacts on both the semiconductors reveals distinctly rectifying behavior of the heterojunction diode. The as-fabricated diode is tested at various temperatures, and the conduction mechanism in the device is analyzed based on the temperature dependent electrical characterizations. In addition, photoresponse characterization reveals that the P-n heterojunction is highly sensitive to a 405 nm laser with a high responsivity of 444 A/W at a reverse bias voltage of 5 V and shows photovoltaic behavior. The heterojunction diode acts as a self-powered photodetector. Our findings show the potential of the MoS2/GaN heterojunction in highly efficient photodetector applications.

Counter-intuitive junction temperature behavior in AlGaN-based deep-ultraviolet light-emitting diodes

The junction temperature, one of the major parameters that strongly affect the performance of light-emitting diodes (LEDs), increases during operation because of the power dissipated as heat within an LED device. Therefore, LED devices with poor characteristics are expected to have higher junction temperatures for the same driving conditions. In this study, an observation contrary to this expectation is presented: a deep-ultraviolet LED device with superior electrical characteristics shows a higher junction temperature at the same input electrical power than a device with poor characteristics. A simple equivalent circuit comprising a diode, a series resistor, and shunt components is employed to elucidate this counter-intuitive observation by considering the possible heat sources inside the LED device. It is found that the junction temperature is mainly dominated by the power dissipated at the diode instead of the other possible heat sources including the Joule heating effect of the resistive components.

Optical, electrochemical and electrical properties of p-N,N-dimethyl-amino-benzylidene-malononitrile thin films

A donor-acceptor small organic molecule, p-N,N-dimethyl-amino-benzylidene-malononitrile (DABMN), has been synthesized and successfully prepared in thin films using spin coating technique. The thin film of DABMN exhibited semiconductor behavior with an optical band gap of about 2.27 eV. The photoluminescence spectrum was exhibited a strong red emission. The energy levels of lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) were determined by experimental calculation from cyclic voltammetry. The electrical performance of the ITO/DABMN/Al structure device was evaluated through current-voltage characteristics and showed a typical Schottky diode behavior with good charge mobility. The charge density associated with the DABMN film was calculated from the capacitance-voltage measurements.

Morphological, optical and photovoltaic characteristics of MoSe2/SiOx/Si heterojunctions

This work reports the effect of different processing parameters on the structural and morphological characteristics of MoSe2 layers grown by chemical vapour deposition (CVD), using MoO3 and Se powders as solid precursors. It shows the strong dependence of the size, shape and thickness of the MoSe2 layers on the processing parameters. The morphology of the samples was investigated by field emission scanning electron microscopy (FESEM) and the thickness of the deposited layers was determined by atomic force microscopy (AFM). Raman and photoluminescence (PL) spectroscopies were used to confirm the high quality of the MoSe2 layers. Surface composition was examined by photoelectron spectroscopy (XPS). Moreover, the MoSe2/SiOx/Si heterojunctions exhibit diode behaviour, with a rectification ratio of 10, measured at ±2.0 V, which is due to the p-i-n heterojunctions formed at the p-Si/SiOx/MoSe2 interface. A photovoltaic effect was observed with a short circuit current density (Jsc), open circuit voltage (VOC) and efficiency of −0.80 mA/cm2, 1.55 V and 0.5%, respectively. These results provide a guide for the preparation of p-i-n heterojunctions based on few-layer MoSe2 with improved photovoltaic response.

Assessment of hybrid integration of a tunneling diode

A quantum well laser diode (QWLD) and tunneling diode (TD) integrated to make hybrid of a single-mode distributed feedback laser. Which can emit coherent radiation by the action of a laser at around 1060 nm or at around 1310 nm on based GaAs substrate or P-based substrate respectively. At room temperature direct current characteristics were steady and examined. The behavior of Tunneling diode were steady on the different parameter of electrical and optical, controlled by voltage. When the voltages increased a wide hysteresis loop are obtained. Within a very small voltage range we can on and off the laser by the help of tunneling diode.

Effect of the Si doping on the properties of AZO/SiC/Si heterojunctions grown by low temperature pulsed laser deposition

The structural and photoelectrical properties of Al-doped ZnO (AZO)/SiC/p-Si and AZO/SiC/n-Si heterojunctions, fabricated at low temperature by pulsed laser deposition, were investigated by means of a number of techniques. Raman analysis indicates that SiC layers have the cubic 3C-SiC phase, whilst X-ray diffraction measurements show that AZO films exhibit a hexagonal wurtzite structure, highly textured along the c-axis, with average crystallites size of 35.1 nm and lattice parameter c of 0.518 nm. The homogeneous and dense surface morphology observed by scanning electron microscopy was confirmed by atomic force microscopy images. Moreover, UV–Vis-NIR spectra indicated a high transmittance of SiC films in the region 550–2500 nm, about 80% transmittance of AZO films in the 450–1000 nm region, and optical band gaps in good agreement with literature. These results prove that pulsed laser deposition is a low-cost technique suitable to grow SiC and AZO films with excellent material properties. The effect of the Si doping on the current transport mechanisms in the heterojunctions was investigated by current-voltage measurements under dark and white light illumination. Both heterojunctions exhibit a diode behaviour and relatively low leakage current, with a noticeable superiority for the AZO/SiC/n-Si device also under illumination, with an illumination/dark ratio of about 400. Our results indicate that the AZO/SiC/p-Si heterojunctions, with higher values of ideality factor, series resistance and lower rectifying ratio, have a complex current transport compared to the diodes grown on n-type Si. Additionally, capacitance-voltage measurements and Mott-Schottky plot allowed to determine a built-in potential of 0.51 V for the Al/AZO/SiC/p-Si/Al device.

Synthesis of an electrically conductive square planar copper(ii) complex and its utilization in the fabrication of a photosensitive Schottky diode device and DFT study

A naphthalene based square planar copper(ii) complex shows significant C–H⋯π interactions to form a supramolecular chain structure. The complex shows efficient charge transport and reveals Schottky barrier diode behavior.

Fabrication of Cu(ii) based halobenzoate appended ladder polymers with efficient charge transport properties

Two novel 1D Cu(ii) CPs based on halo-substituted benzoate ligands together with an N-donor bpe spacer ligand exhibit high electrical conductivity and reveal Schottky diode behaviour.

Synthesis, characterization, self-assembly and non-ohmic Schottky barrier diode behaviors of two iron(iii) based semiconductors with theoretical insight

Schottky barrier diodes have been fabricated using two iron(iii) Schiff base complexes. The total and partial DOS values have been calculated using DFT to calculate the band gaps in these complexes.

Improvement of the electron transport behavior in quantum-dot light-emitting diodes using a low-temperature processable ZnO

Zinc oxide (ZnO) is a commonly used electron transport layer in quantum-dot light-emitting diodes (QLEDs). In this study, we used a highly conductive ZnO film via a low-temperature process to improve the electron transport behavior of the QLEDs. The electron transport behavior of ZnO film was investigated from the electron only device, and the origin of high conductivity was figured out using x-ray photoelectron spectroscopy. We found that the oxygen vacancy, which can improve the carrier transport in ZnO film, was increased according to reduce the process temperature of ZnO. Meanwhile, the hydroxyl group, which contribute to the quenching effect, was decreased according to reduce the process temperature of ZnO. Therefore, high-performance QLEDs were fabricated using the low-temperature processed ZnO, and it showed an improved luminance and current efficiency in a full current range. The maximum luminance and current efficiency of the devices were measured as 65,391 Cd/m2 and 2.48 Cd/A, respectively. Moreover, the lifetime of the device was improved due to the low-temperature process. Therefore, we suggest that a highly conductive ZnO film could be formed through a low-temperature process, and it can improve the performance of QLEDs.

Ferroelectric Diode Effect with Temperature Stability of Double Perovskite Bi2NiMnO6 Thin Films.

Double perovskite Bi2NiMnO6 (BNMO) thin films grown on p-Si (100) substrates with LaNiO3 (LNO) buffer layers were fabricated using chemical solution deposition. The crystal structure, surface topography, surface chemical state, ferroelectric, and current-voltage characteristics of BNMO thin films were investigated. The results show that the nanocrystalline BNMO thin films on p-Si substrates without and with LNO buffer layer are monoclinic phase, which have antiferroelectric-like properties. The composition and chemical state of BNMO thin films were characterized by X-ray photoelectron spectroscopy. In the whole electrical property testing process, when the BNMO/p-Si heterojunction changed into a BNMO/LNO/p-Si heterojunction, the diode behavior of a single diode changing into two tail to tail diodes was observed. The conduction mechanism and temperature stability were also discussed.

Tunable Current Rectification and Selectivity Demonstrated in Nanofluidic Diodes through Kinetic Functionalization.

The possibility of tuning the current rectification and selectivity in nanofluidic diodes is demonstrated both experimentally and theoretically through dynamically functionalizing a conical nanopore with poly-l-lysine. We identified an optimum functionalization time equivalent to optimum modification depth that assures the highest rectification degrees. Results showed that the functionalization time-dependent rectification behavior of nanofluidic diodes is dominated by the properties of current at positive voltages that in our electrode configuration indicate the "on" state of the diode and accumulation of ions in the nanopore. The functionalization time also tunes the ion selectivity of the diode. If the functionalization time is sufficiently short, an unusual depletion of counterions near the bipolar interface results in a cation-selective nanopore. However, a further increase in the duration of functionalization renders a nanopore that is an anion-selective nanopore. The dynamic functionalization presented in this Letter enables tuning ion selectivity of nanopores.

Bacteriophage M13 Aggregation on a Microhole Poly(ethylene terephthalate) Substrate Produces an Anionic Current Rectifier: Sensitivity toward Anionic versus Cationic Guests.

Bacteriophage material (M13, wild-type) deposited as a film onto a poly(ethylene terephthalate) (PET) substrate (6 μm thick with a 20 μm diameter laser-drilled microhole) has been investigated for ion conductivity and ionic current rectification effects for potential applications in membranes. The M13 aggregate membrane forms under acidic conditions (in aqueous 10 mM acids) and behaves like a microporous anion conductor with micropores defined by the packing of cylindrical virus particles. Asymmetric deposition on the PET film substrate in conjunction with semipermeability leads to anionic diode behavior. Typical rectification ratio values are around 10 (determined at ±1 V) in aqueous 10 mM acids. Cationic guest species (aqueous Cu2+, Co2+, Ag+) consistently lead to a rectification minimum at 0.5 mM guest concentration. In contrast, anionic guest species (indigo carmine) lead to a similar rectification minimum already at 5 μM concentration. The behavior is proposed to be associated with cation exclusion effects on transport.

Temperature performance of InGaAs/InGaAlAsTemperature performance of InGaAs/InGaAlAs laser diodes with δ-doping active region

The optical gain performance of 1530-1565 nm laser diodes with active regions containing p-doped barrier layers has been investigated. We have studied the threshold current density and differential quantum efficiency in wide temperature range and compared modal gain behaviour of laser diodes made of heterostructure with delta-doped barrier layers by carbon at level of 1012 cm-2 and heterostructure with undoped barrier layers.