Current Transport Properties Research Articles

Influence of 700 keV O3+ ion implantation on current transport properties of Cr/p-GaN SBD’s

In the present study we show a detailed investigation into the influence of 700 keV O3+ ion implantation in Cr/p-GaN SBDs on electrical characteristics / current transport properties. Also the damage events along the trajectory of the ion beam were quantitatively estimated through SRIM and TRIM simulations. The Current-voltage (I-V) characteristics were analyzed using different methods such as Cheung and Cheung's method and Norde’s method to obtain different electrical parameters. The values of n and ϕB decrease up to a fluence of 1 × 1014 ions cm−2, and show a fractional increase at a fluence of 1 × 1015 ions cm−2. Further, a drastic increase in values of series resistance (RS ) of SBDs with an increase in fluence was observed. In the forward-bias voltage regions, the Cr/p-GaN SBDs conduction mechanism shows an increasingly ohmic behavior with an increase in fluence, which may be attributed to thermally generated carriers. At low voltage, the reverse current conduction mechanism is due to Poole-Frenkel emission. For the high voltage region, Schottky emission mechanism becomes more prominent. The changes in electrical parameters are closely related to the defect and damage profiles estimated through SRIM/TRIM simulations, which are strongly dependent on the dose of the 700 keV O3+ ion implantation. Additionally, we found that at high doses, the charge transport mechanism changes, with additional defects affecting not only the thermionic emission mechanism but also various current transport mechanisms.

Highly Efficient Spin Current Transport Properties in Spintronic Devices Based on Topological Insulator

AbstractRecently, topological insulators (TIs) have regained extensive attention in spintronics due to their potential applications in new‐generation spintronic devices, following the discovery of the quantum Hall effect and quantum anomalous Hall effect, which introduce the topological concept. In this review, the exotic spin transport phenomena are explored in TIs. The review offers a concise overview of the fundamental principles of TIs, followed by an exploration of diverse fabrication methods for TI materials. Characterization techniques of the topological surface states are also presented. The review delves into the intriguing spin current transport phenomena, focusing on spin‐to‐charge and charge‐to‐spin conversions in TI/ferromagnet bilayers, respectively. The review culminates summarizing key insights and project future directions for research on spin transport phenomena in TIs, emphasizing practical implications.

Towards high-field applications: high-performance, low-cost iron-based superconductors.

High magnetic fields play a crucial role in advancing basic sciences, fusion energy, and magnetic resonance imaging systems. However, the widespread use of high-field magnets requires affordable high-temperature superconducting wires that can carry large supercurrents. Iron-based superconductors offer an economically attractive solution to push forward important yet costly scientific programs, such as nuclear fusion reactors and next-generation particle accelerators. In this review, we start with the fabrication of iron-based superconducting wires and tapes and continue to discuss several key factors governing the current transport properties. State-of-the-art wires and tapes are introduced with emphasis on grain boundary characteristics, flux pinning, and anisotropy. The architecture of flexible conductors enables low cost, high mechanical strength, and high thermal stability. Recent progress in practical applications, including superconducting joints and insert coils, is also reviewed. Finally, we propose several key questions faced by iron-based superconductors in future practical applications.

Scrutinizing Current Transport Properties in Vertical GaN Schottky Junctions

Scrutinizing Current Transport Properties in Vertical GaN Schottky Junctions

Structural and Optical Properties of Sol–Gel-Spin Coating Nanostructured Cadmium Zinc Nickel Phosphate (CZNP) Film and the Current Transport Properties of CZNP/p-Si-Based Diode

In this work, the growth of CdZnNiPO (CZNP) thin films on glass and p-Si substrates using the sol–gel spin coating method was successfully achieved. The structure, and morphology of the CZNP films were analyzed using XRD and FE-SEM. The optical absorbance behavior, energy gap, refractive indices, optical dielectric, optical conductivity, and optical electronegativity of the films were studied using the UV–Vis optical spectroscopy technique. XRD analysis shows that zinc phosphate accommodates cadmium ions by replacing zinc ions in the unit cell, resulting in oxygen vacancies that maintain charge neutrality. Scanning electron microscope images reveal the presence of a highly interconnected and well-organized nano CZNP framework. The optical absorption studies of CZNP films were conducted in the wavelength range of 190–2500 nm. The results show both direct and indirect energy band gaps of 1.69 and 2.89 eV, respectively, were employed in the prepared system. The current–voltage-temperature (I-V-T) characteristics of the CZNP/p-Si junction was analyzed in dark mode. The device transport ideality factor, barrier height, and series resistance were identified.

Temperature profiles of field-aged photovoltaic modules affected by optical degradation

Moisture ingress into PV module in the presence of ultraviolet radiation, high temperature, and other environmental stressors can affect the optical integrity of the PV module. Optical degradation can take the form of delamination, discolouration of encapsulant, metal grids corrosion, and trapped moisture or chemical species. This can influence the photon absorption and current transport properties in the PV module bulk, which can affect the module operating temperature. In the present work, the relationship between optical degradation and temperature sensitivity of 20-year-old multicrystalline silicon field-aged PV modules have been investigated. The selected PV modules were characterized using visual inspection, current-voltage (I–V) characterization, temperature coefficients profiling, current resistivity profiling, infrared (IR) thermal, ultraviolet fluorescence (UV–F), and electroluminescence (EL) imaging. PV modules affected by optical degradation show weak fluorescence and luminescence signal intensities. The average difference in cell temperature (ΔT) between the warmest and coldest cell for the PV modules investigated was found to be around 10 ± 2 °C and the average power degradation rate was approximately 0.8% per year. The underlying factor for the observed degradation is attributed to the degradation in the temperature coefficients of open circuit voltage (βVoc) and maximum power point voltage (βVmpp). The average temperature coefficient of efficiency (βηm) of the modules was found to be around −0.5%/°C. Finally, a temperature dependent resistivity method for extracting temperature coefficients from IR thermal data of PV modules has been proposed.

High-performance Fe(Se,Te) films on chemical CeO2-based buffer layers

The fabrication of a Fe-based coated conductor (CC) becomes possible when Fe(Se,Te) is grown as an epitaxial film on a metallic oriented substrate. Thanks to the material’s low structural anisotropy, less strict requirements on the template microstructure allow for the design of a simplified CC architecture with respect to the REBCO multi-layered layout. This design, though, still requires a buffer layer to promote the oriented growth of the superconducting film and avoid diffusion from the metallic template. In this work, Fe(Se,Te) films are grown on chemically-deposited, CeO2-based buffer layers via pulsed laser deposition, and excellent properties are obtained when a Fe(Se,Te) seed layer is used. Among all the employed characterization techniques, transmission electron microscopy proved essential to determine the actual effect of the seed layer on the final film properties. Also, systematic investigation of the full current transport properties J(θ, H, T) is carried out: Fe(Se,Te) samples are obtained with sharp superconducting transitions around 16 K and critical current densities exceeding 1 MA cm−2 at 4.2 K in self-field. The in-field and angular behavior of the sample are in line with data from the literature. These results are the demonstration of the feasibility of a Fe-based CC, with all the relative advantages concerning process simplification and cost reduction.

Reconfigurable spin tunnel diodes by doping engineering VS2 monolayers.

We propose a reconfigurable spin tunnel diode based on a small spin-gapped semiconductor (non-doped VS2 monolayer) and semi-metallic magnets (doped VS2 monolayer) separated by a thin insulating tunneling barrier (h-BN). By using first-principles calculations assisted by the nonequilibrium Green's function method, we have carried out a comprehensive study of spin-dependent current and spin transport properties while varying the bias. The device exhibited a magnetization-controlled diode-like behavior with forward-allowed current under antiparallel magnetizations and reverse-forbidden current under parallel magnetizations at the two electrodes. The threshold voltage is tunable by the hole doping density of VS2 monolayers. The doping effect on VS2 monolayers indicates that the magnetic moments, the Heisenberg exchange parameters and Curie temperatures can be monotonically reduced by a larger hole doping density. Our study on VS2 heterostructures has presented a simple and practical device strategy with very promising applications in spintronics.

Interface effects on the current transport properties of multi-layered (Ba, K)Fe2As2 superconducting wires

Multi-layered iron-based superconducting wires were developed using a tape-in-tube method. The interface between the superconducting filament and the Ag matrix is found to play an important role in the phase homogeneity and current carrying performance.

Molecular dynamics simulations of fluoroethylene carbonate and vinylene carbonate as electrolyte additives for Li-ion batteries

ABSTRACT Contemporary electrolyte additives have captivated the attention of researchers since additives were reported to play a very crucial role in supporting the formation of an effective solid electrolyte interphase (SEI) in the case of silicon if used as an anode. The choice of a good solvent with additives demonstrates a significant impact on the solvation and diffusivity of lithium ions. Fluoroethylene carbonate (FEC) and Vinylene carbonate (VC) were extensively used additives for increasing the lifespan of Li-ion batteries (LIBs). In the current study, structural, dynamical, and transport properties of six different systems were investigated by applying classical molecular dynamics (MD) simulations. The properties obtained from the simulations suggested system E consisting of DMC, 1M LiPF, and 10% FEC, to be the best medium for the electrolytes for LIBs, since the diffusion coefficient of Li ions and ionic conductivity of LiPF were estimated to be of high values for the system E. However, before the evaluation of the transport properties, the structural properties in terms of radial distribution functions and spatial distribution functions were evaluated for DMC molecules with reference to DMC, Li, and PF ions. The structure data were also found to be in fair agreement with experimental and previous simulation results reported so far. Based on the finding of this study, it was suggested that DMC as a solvent with a 10% FEC additive could be considered a good medium for electrolytes for the improved performance of LIBs compared to VC as an additive to DMC.

Electrically driven whispering-gallery-mode microlasers in an n-MgO@ZnO:Ga microwire/p-GaN heterojunction.

In emerging miniaturized applications, semiconductor micro/nanostructures laser devices have drawn great public attentions of late years. The device performances of micro/nanostructured microlasers are highly restricted to the different reflective conditions at various side surfaces of microresonators and junction interface quality. In this study, an electrically driven whispering-gallery-mode (WGM) microlaser composed of a Ga-doped ZnO microwire covered by a MgO layer (MgO@ZnO:Ga MW) and a p-type GaN substrate is illustrated experimentally. Incorporating a MgO layer on the side surfaces of ZnO:Ga MWs can be used to reduce light leakage along the sharp edges and the ZnO:Ga/GaN interface. This buffer layer incorporation also enables engineering the energy band alignment of n-ZnO:Ga/p-GaN heterojunction and manipulating the current transport properties. The as-constructed n-MgO@ZnO:Ga MW/p-GaN heterojunction device can emit at an ultraviolet wavelength of 375.5 nm and a linewidth of about 25.5 nm, achieving the excitonic-related recombination in the ZnO:Ga MW. The broadband spectrum collapsed into a series of sharp peaks upon continuous-wave (CW) operation of electrical pumping, especially for operating current above 15.2 mA. The dominant emission line was centered at 378.5 nm, and the line width narrowed to approximately 0.95 nm. These sharp peaks emerged from the spontaneous emission spectrum and had an average spacing of approximately 5.5 nm, following the WGM cavity modes. The results highlight the significance of interfacial engineering for optimizing the performance of low-dimensional heterostructured devices and shed light on developing future miniaturized microlasers.

Domain reversal and current transport property in BiFeO3 films

The electrical properties and domain reversal in BiFeO3 ferroelectric films were studied using sandwiched heterostructures and piezoresponse force microscopy. A robust polarization state was observed, combined with a switchable domain pattern and a remanent polarization of approximately 100 μC cm−2. In addition, domain reversal was explored using scanning probe microscopy. The results show that dipoles could be reversed along the direction of the electric field under a negative tip bias, leading to carrier gathering near the domain walls. The enhanced conductivity near the domain walls was owing to the discontinuous polarization boundary conditions. In addition, typical diode-like current transport properties are sensitive to various temperature conditions, which is attributed to the Schottky barriers at the contact interface. These findings extend the current understanding of domain texture reversal in ferroelectric films and shed light on their potential applications for future ferroelectric random-access memory operations over a wide temperature range.

Current transport properties of Pt/n-GaN Schottky diodes with ZnO interlayers

In this work, atomic layer deposition (ALD) was used to grow 20-nm thick ZnO interlayers (IL) on a GaN substrate at 150 and 200 °C and the current transport mechanisms of vertical Pt/ZnO/n-GaN Schottky diodes were investigated. A high density of surface state was observed for the ZnO layer grown at 200 °C. An analysis of the forward current–voltage (I–V) data considering various transport mechanisms demonstrated that the thermionic emission and the tunneling components attributed to the total current for the ZnO layer grown at 150 °C. In contrast, it was observed that the tunneling component mainly caused the current conduction in the ZnO layer grown at 200 °C. Additionally, an analysis of the reverse I–V characteristics exhibited a high density of surface defects on the ZnO layer grown at 200 °C. This study demonstrated that the ALD growth temperature of ZnO IL significantly affects the I–V characteristics of GaN Schottky diodes.

Temperature Dependent Current Transport Mechanism of Photopolymer Based Al/NOA60/p-Si MPS Device

A photopolymer based Al/Norland Optical Adhesive 60 (NOA60)/p-Si MPS (metal-polymer-semiconductor) device was fabricated by a combination of vacuum evaporation and smear technique. The current transport properties of the device were investigated by using the forward bias current–voltage (I-V) characteristic in the temperature range of 80–300 K. The cross-sectional structure of polymer/semiconductor was revealed by the scanning electron microscope (SEM) image and it was seen that the NOA60 photopolymer was tidily coated on the p-Si surface. According to the I-V measurements at room temperature, the MPS device exhibits a good rectification ratio of 8140 at ± 1 V. The temperature-dependent I-V measurements (I-V-T) were analyzed based on the thermionic emission (TE) theory and an abnormal increase in zero-bias barrier height (BH) and a decrease in ideality factor (n) was observed with increasing temperature. Additionally, two different linear regions with distinct values from the theoretical value of the Richardson constant (A*) were observed in the conventional Richardson plot. Such deviations from the ideal TE theory have been attributed to the effect of BH inhomogeneities. Gaussian distribution (GD) of the BH model has applied the I-V-T results and the double GD BH with mean values of 0.75 ± 0.08 eV (80–140 K) and 1.02 ± 0.11 eV (140–300 K) were calculated. Moreover, the A* value of 31.4 A/cm2K2 was calculated close to the known value of p-Si from the modified Richardson plot. Thus, it has been concluded that the current transport of the Al/NOA60/p-Si MPS device can be explained by TE with a double GD BH model for a wide temperature region.

Spin Seebeck effect driven by thermal flux in two-dimensional ferromagnets

The spin Seebeck effect is a novel indirect thermoelectric conversion phenomenon, in which magnetic materials play an important role, that is distinct from the traditional direct thermoelectric conversion method. In this paper, we studied the spin Seebeck effect driven by thermal flux in two-dimensional ferromagnets and derived the spin-dependent Seebeck coefficient and the spin Seebeck coefficient contributed by conduction electrons in a ferromagnet based on the non-equilibrium linear irreversible thermodynamics and the Boltzmann linear theory. The spin Seebeck coefficients of six two-dimensional ferromagnetic materials (including manganese halides and transition metal chalcogenides) were numerically calculated. A largest spin Seebeck coefficient is found for MnCl3 to be 1600 μV/K in the range of temperature from 50 to 120 K, which is even larger than that of known CrI3 and CrGeTe3. The present study on the heat flow-spin current transport properties of ferromagnets could have great significance for the thermoelectric applications in spintronics.

P‐10.1: Electro‐optical properties investigation in AlGaInP‐based Red Micro‐LED devices

AlGaInP‐based light‐emitting diode (LED) arrays are a promising technology in a wide range of applications. The electrical characteristics and current transport properties of AlGaInP‐based red micro‐light‐emitting diodes were investigated using current‐voltage (I‐V) measurements. The ideality factor of device was obtained, indicating that the current conduction mechanism is defect‐assisted tunneling, which forms parasitic current paths across the active region. These results were consistent with the parasitic resistances obtained from the measured current‐voltage curves. It was attributed that the defects originated from sidewall damage of the active layer. The EL spectrum of the red micro‐LED is characterized by narrow emission width of ~19 nm.

Characterization and evaluation of current transport properties of power SiC Schottky diode

This paper presents the characterization and evaluation of current transport properties of power SiC Schottky diode. The evaluation of the main Schottky diode properties is based on the proposed advanced model. This model allows assessing the effect of particular current transport mechanisms with high accuracy. The presence and influence of tunneling current in I-V characteristics are evident, mainly for low temperatures. Unlike previously published results, the proposed model provides areasonable slight decrease of Schottky barrier height with increasing temperature due to the narrowing of the energy bandgap. The results and model are validated by finite element method (FEM) electrophysical simulations. Evaluated parameters of SiC Schottky diode, such as Schottky barrier height of 1.28 eV and Richardson constant of 1.46 × 106 Am−2K−2 are in good agreement with recent research and FEM simulations.

Quantitative evaluation of DC voltage–current characteristics of a high temperature superconducting stator winding located in silicon steel core at 77 K

In this paper, we report on the quantitative characteristics of the DC current transport property of a superconducting bismuth strontium calcium copper oxide (BSCCO) stator winding that is used in a superconducting motor. The winding is in a slot of silicon steel core, and the DC voltage of such a winding is measured as a function of the transport current in atmospheric liquid nitrogen. Precise distribution of the magnetic field vector on the winding is also obtained using a three-dimensional finite element method, and thereafter used for the quantitative calculation of the local electric field with the aid of nonlinear and distributed circuits. The total (end-to-end) voltage of the winding is obtained by summing up the local value. It is demonstrated that the developed analysis procedure reproduces the measured results of the DC voltage vs. current characteristics even though the tape experiences a complicated magnetic field vector. Our method is effective for the precise design of a high-temperature superconducting stator.

P‐63: Electro‐optical properties investigation in AlGalnP‐based Red Micro‐LED devices

AlGalnP‐based light‐emitting diode (LED) arrays are a promising technology in a wide range of applications. The electrical characteristics and current transport properties of AlGaInP‐based red micro‐light‐emitting diodes were investigated using current‐voltage (I‐V) measurements. The ideality factor of device was obtained, indicating that the current conduction mechanism is defect‐assisted tunneling, which forms parasitic current paths across the active region. These results were consistent with the parasitic resistances obtained from the measured current‐voltage curves. It was attributed that the defects originated from sidewall damage of the active layer. The EL spectrum of the red micro‐LED is characterized by narrow emission width of ~19 nm

Electrical and carrier transport properties of Ti/α-amylase/p-InP MPS junction with a α-amylase polymer interlayer

This paper demonstrates the electrical and current transport properties of prepared Ti/α-amylase/p-InP metal/polymer/semiconductor (MPS) junction by current–voltage (I–V) approach. The microstructure of the fabricated MPS junction is confirmed by transmission electron microcopy (TEM) measurement. The MPS junction exhibited a good rectification nature over the Ti/p-InP metal/semiconductor (MS) junction. The derived barrier height (BH) of MPS junction (0.78 eV) is higher than the MS junction (0.70 eV), that indicates the BH is influenced by the polymer layer. The BH is extracted by the I–V, Z(V)–Vd plot, Cheung’s function, α(V)–V plot, Norde method and Ψs–V plot and found the values are comparable with one another, which indicates their steadiness and validity. The estimated interface state density (NSS) of the MPS junction is less than the MS junction, suggesting that the α-amylase layer decreased the NSS value. The forward log (I)–log (V) plot of the MS and MPS junctions reveals the ohmic nature at lower-bias region and space-charge-limited conduction at higher-bias region. Results reveal that the reverse leakage current conduction mechanism of the MS and MPS junctions is governed by Poole–Frenkel emission in lower-bias region, whereas, at higher bias region, Schottky emission is dominant current conduction mechanism. These exploration results establish that the α-amylase polymer layer is potential for use in organic–inorganic devices.