Temperature Dependence Of Current Research Articles

A Cross-Scale Electrothermal Co-Simulation Approach for Power MOSFETs at Device-Package-Heatsink-Board Levels.

This paper proposes a cross-scale simulation approach for evaluating the steady-state electrothermal performance of power MOSFETs at the device-package-heatsink-board (DPHB) level. A co-simulation framework is designed by employing the iterative process of power loss and chip temperature to bridge the device and package-heatsink-board (PHB) level simulators. As a result, the cross-scale electrothermal coupling effect within multilevel settings is considered. Correspondingly, variation values in chip temperature and temperature-dependent drain current can be obtained at various voltage biases, level settings, and DPHB structural parameters, incorporating cross-level physical insights. The simulation results are compared with existing methods, and their features and limitations are discussed. Additionally, this paper also derives an empirical equation from the co-simulations to characterize the relationship between the drain current and the chip temperature under different operations exactly. A commercial MOSFET with TO-220F packaging is implemented in experiments to extract the chip temperature and drain current in electrothermal equilibrium. The method comparisons and fair agreement among simulations, equations, and measurements presents the proposed approach as generalized and powerful for describing variations in chip temperature and drain current considering from micrometer devices to millimeter packages-heatsinks-PCB boards, thus providing effective support for DPHB-level co-design.

Exploring asymmetric fission in 180Hg⁎ compound nucleus using dynamical cluster-decay model

The observed asymmetric fission of the 180Hg⁎ compound nucleus challenges conventional expectations of symmetric fission, which are attributed to the presence of shell closures at Z=40 (semi-magic) and N=50 (magic). To comprehend this novel phenomenon, the dynamical cluster-decay model has been employed. For the first time, this model incorporates the bulk and neutron-proton asymmetry coefficients of the nuclear shape-dependent mass excess formula which are tuned recently to the ground state mass excess data of AME2020 and/or FRDM(2012) along with the temperature dependence for the nuclear shape and the surface energy coefficient of the nuclear proximity potential. The calculations have considered nuclear shapes as both spherical and deformed (quadrupole), with and without temperature dependence for the quadrupole deformation. A new minimum appears in the symmetric mass region of the fragmentation potential for masses (80, 100), when the fragments are deformed and optimally oriented, at an energy lower than that obtained for masses (90, 90) where the fragments are assumed to be spherical or nearly spherical at higher temperatures. This new minimum seems equivalent to the appearance of a new shell gap with deformation and is responsible for the asymmetric fission of 180Hg⁎. The most probable fission channel and the transition from asymmetric to symmetric mass distribution at higher excitation energies are consistent with experiments for the current temperature dependence assigned to the quadrupole deformation parameter.

Demonstration of a violet-distributed feedback laser with fairly small temperature dependence in current-light characteristics

We have developed a GaN-based distributed feedback laser diode (DFB-LD) with the detuning of +5 nm to obtain a smaller temperature dependence of the threshold current. We found that the current-light characteristics almost overlapped up to 300 mW between 25 °C and 80 °C. The estimated characteristic temperature is about 2550 K. These indicate that our DFB-LD is promising for applications that require small temperature dependence in the output power and oscillation wavelength at constant operation current without precise temperature control.

Study of optical float-zone grown gallium oxide Schottky barrier diode

β−Ga2O3 based lateral Schottky barrier diodes are fabricated using Ni/Au as Schottky contact and Ti/Au as Ohmic contact. The Sn-doped β−Ga2O3 sample is grown by the optical float-zone technique. The effect of trenches, which are used for mesa isolation, on breakdown voltage is investigated. The device shows near-ideal characteristics in terms of built-in potential. The parasitic series and shunt resistances are extracted, and their dependency on temperature is established. Modeling of temperature-dependent reverse leakage current is demonstrated using the thermionic emission model, Poole–Frenkel emission model, and Fowler-Nordheim tunneling mechanism. The procedure to extract relevant parameters is explained in terms of bias and temperature dependency. The combined model shows excellent agreement with experimental data over a wide range of bias and temperature. The maximum electric field of 2.3 MV cm−1 is achieved.

ВЛИЯНИЕ ТОЛЩИНЫ ПЛЕНОК ПОЛИДИФЕНИЛЕНФТАЛИДА НА СПЕКТР ТОКОВ ДЕПОЛЯРИЗАЦИИ МНОГОСЛОЙНЫХ СТРУКТУР

The depolarization currents of multilayer polymer films of polydiphenylene phthalide were measured using the thermally stimulated depolarization (TSD) method in the range from 170 to 400 K. The solution concentration was 2.5 and 5 wt.%. Each layer of polymer film was pre-dried at room temperature, then annealed in an oven. The number of layers of polymer film was 1, 2, 3 and 7 layers for 2.5 wt.%. and 1, 2, 3, 5 and 7 layers for 5 wt.%. The polarizing electric field strength was 2.5 × 105 V/cm. The rate of temperature change was 5 K/min. Based on experimental data, the dependence of the temperature of the position of the maximum peak of the depolarization current, the maximum values of the peaks of the depolarization currents, the values of the released charge and the activation energy of relaxation processes on the number of layers of the polymer film is shown. The temperature dependences of depolarization currents revealed two regions for a solution concentration of 2.5 wt.%. and one area for 5 wt.%. The first region is interpreted in the dipole charge approximation. The second region is explained by the presence of a wide distribution of traps occupied by injected charges. Interlayer polarization is observed in inhomogeneous dielectrics and is caused by differences in the electrical conductivity and dielectric constant of individual particles (or microparticles) of the dielectric. In such dielectrics, when an electric field is applied at the interface between its various components, charge will accumulate, which is equivalent to the creation of polarization. The results for the temperature dependences of the TSD currents of the samples showed that the total accumulated charge in the volume increases as the number of polymer layers increases. The reason for such a high concentration of trapped charges is most likely due to the presence of a wide distribution of traps occupied by injected charges. Moreover, the magnitude of the released charge is greater for samples prepared from a polymer solution with 2.5 wt. % This effect depends on the thickness of the polymer films. Namely, the thinner the films, the more charged particles penetrate the interface between the films.

Current transport mechanism of lateral Schottky barrier diodes on β-Ga2O3/SiC structure with atomic level interface

Heterogeneous integration of β-Ga2O3 on highly thermal conductive SiC substrate by the ion-cutting technique is an effective solution to break the heat-dissipation bottleneck of β-Ga2O3 power electronics. In order to acquire high-quality β-Ga2O3 materials on SiC substrates, it is essential to understand the influence of the ion-cutting process on the current transport in β-Ga2O3 devices and to further optimize the electrical characteristics of the exfoliated β-Ga2O3 materials. In this work, the high quality of β-Ga2O3/SiC structure was constructed by the ion-cutting process, in which an amorphous layer of only 1.2 nm was formed between β-Ga2O3 and SiC. The current transport characteristics of Au/Pt/Ni/β-Ga2O3 Schottky barrier diodes (SBDs) on SiC were systematically investigated. β-Ga2O3 SBDs with a high rectification ratio of 108 were realized on a heterogeneous β-Ga2O3 on-SiC (GaOSiC) substrate. The net carrier concentration of the β-Ga2O3 thin film for GaOSiC substrate was down to about 8% leading to a significantly higher resistivity, compared to the β-Ga2O3 donor wafer, which is attributed to the increase in acceptor-type implantation defects during the ion-cutting process. Furthermore, temperature-dependent current–voltage characteristics suggested that the reverse leakage current was limited by the thermionic emission at a low electric field, while at a high electric field, it was dominated by the Poole–Frenkel emission from E3 deep donors caused by the implantation-induced GaO antisite defects. These results would advance the development of β-Ga2O3 power devices on high thermal conductivity substrate fabricated by ion-cutting technique.

A Bifunctional Wearable Sensor Based on a Nanoporous Membrane for Simultaneous Detection of Sweat Lactate and Temperature.

Wearable sensors for non-invasive, real-time detection of sweat lactate have far-reaching implications in the fields of health care and exercise physiological responses. Here, we propose a wearable electrochemical sensor with gold nanoelectrode arrays fabricated on the nanoporous polycarbonate (PC) membrane by encapsulating lactate oxidase (LOx) in chitosan (CS) hydrogel for detecting body temperature and sweat lactate concurrently. Flexible gold nanoporous electrodes not only enhance electrode area but also offer a nanoconfined space to accelerate the catalytic reaction of LOx and control substrate concentration on the surface of LOx to decrease substrate inhibition. The proposed sensor has a long durability of 13 days and better selectivity for the detection of sweat lactate over a wide linear range (0.01-35 mM) with a low detection limit (0.144 μM). Furthermore, temperature-dependent transmembrane currents passing through the sensor are used to estimate body temperature. We then use multiple linear regression to adjust the effect of temperature on lactate detection and succeed in monitoring lactate molecules in sweat and body temperature during exercise.

A quantum fluctuation description of charge qubits

We consider a specific instance of a superconducting circuit, the so-called charge-qubit, consisting of a capacitor and a Josephson junction that we describe by means of the BCS microscopic model in terms of two tunnelling superconducting systems in the strong-coupling quasi-spin formulation. Then, by means of collective observables we derive the Hamiltonian governing the quantum behaviour of the circuit in the limit of a large number N of quasi-spins. Our approach relies on suitable quantum fluctuations, i.e. on collective quasi-spin operators, different from mean-field observables, that retain a quantum character in the large-N limit. These collective operators generate the Heisenberg algebra on the circle and we show that their dynamics reproduces the phenomenological one generated by the charge qubit Hamiltonian obtained by quantizing the macroscopic classical Hamiltonian of the circuit. The microscopic derivation of the emergent, large-N behaviour provides a rigorous setting to investigate more in detail both general quantum circuits and quantum macroscopic scenarios; in particular, in the specific case of charge-qubits, it allows to explicitly obtain the temperature dependence of the critical Josephson current in the strong coupling regime, a result not accessible using standard approximation techniques.

Synthesis and characterization of (1-x)Bi0.9Sm0.1FeO3 - (x)BaZr0.15Ti0.85O3 based solid solution: Temperature-dependent dielectric and impedance properties

Lead-free solid solution of (1-x) Bi0.9Sm0.1FeO3 − (x) BaZr0.15Ti0.85O3 (BSFO − BZT) (x = 0.0, 0.10, 0.15, 0.20, 0.25, 0.50) ceramics were prepared using solid-state reaction method. The structural, morphological, temperature-dependent dielectric properties and leakage current were investigated. The structural investigation revealed the formation of perovskite structure coexisting with tetragonal and rhombohedral phases within (BSFO–BZT) ceramics. The dielectric measurements (within 303 K-773 K) confirmed the existence of a morphotropic phase boundary at x = 0.15 for the (BSFO–BZT) system. The frequency and temperature dependent electrical behavior were explained using Ac conductivity and impedance analysis. The leakage current behavior for all these samples was investigated using both space charge-limited conduction (SCLC) for bulk and Schottky emission (SE) for limited interface conduction approach, whereas the pure BSFO sample was found to be dominated by ohmic conduction, while the BZT-doped samples were dominated by grain boundary-limited conduction.The sample (0.80)Bi0.9Sm0.1FeO3-(0.15)BaZr0.15Ti0.85O3 achieved largest dielectric constant 330 at 10 KHz along with a moderate leakage current density value of 3.54 × 10-5A/cm2 (which is quite lower than pure BSFO) proven its candidacy to develop a stable photovoltaic, multilayer actuators, and ferroelectric memory devices.

Electrical conduction behavior in ferroelectric polymer-based composites incorporating metal halide perovskite

Halide perovskites have established their intriguing performances in optoelectronics and been expanded to energy harvesting application when incorporated into polymers due to their polarization related properties. Yet, fundamental understanding of the electrical conduction behavior of such composites has seldomly been addressed. Herein, composite films employing CH3NH3PbBr3 (MAPB) nanoparticles and ferroelectric polymer poly(vinylidenefluoride-co-trifluoroethylene) [P(VDF-TrFE)] have been investigated upon their conduction behaviors. Both electric field and temperature-dependent currents have been thoroughly analyzed based on hopping and space charge-limited current mechanisms in combination with trap energy and trap density calculation from thermal stimulated depolarization currents. The conduction mechanism of MAPB/P(VDF-TrFE) composite has been established within the frame of band diagram. Our studies, thus, are essential for developing high-performance optoelectronics and energy harvesters based on halide perovskites/polymer composites.

Effect of gamma irradiation on β -Ga2O3 vertical Schottky barrier diode

In this paper, the radiation effect of gamma irradiation (60Co) on the Au/Ni/β-Ga2O3 vertical Schottky barrier diodes (SBDs) was investigated for total doses of about 1 Mrad (Si). The SBDs were characterized by current density–voltage (J–V) and capacitance–voltage (C–V) measurements. Compared with original β-Ga2O3 SBDs, it was found that Schottky barrier height Φb increases from 1.08 to 1.12 eV, the ideality factor n decreases from 1.07 to 1.02, and the specific on-resistance Ron,sp decreases from 3.34 to 2.95 mΩ·cm2 for the irradiated β-Ga2O3 SBDs. In addition, the carrier concentration calculated from the C–V measurements increases slightly after gamma irradiation. The temperature-dependent current–voltage characteristics and conductance-frequency measurements indicate that the Schottky contact interface of β-Ga2O3 SBDs had been slightly improved after irradiation. These results suggest that β-Ga2O3 SBDs have high intrinsic gamma irradiation hardness.

Electrocaloric effect, pyroelectric response and energy storage performance of lanthanum-modified PZT relaxor ferroelectric ceramic

Pb0·85La0·10Zr0·60Ti0·40O3 ferroelectric ceramic system was synthesized via the conventional solid-state reaction sintering route. A systematic study on the pyroelectric response, electrocaloric effect and energy storage properties has been carried out in a wide temperature range, in order to explore its multifunctional features. The obtained results from X-ray diffraction technique, performed at room temperature, revealed the coexistence of two ferroelectric phases governed by the tetragonal (P4mm) and monoclinic (C1m1) symmetries. The pyroelectric behavior of the studied sample has been analyzed by the static method, from the temperature dependence of the pyroelectric current. The electrocaloric response as well as the energy storage performance have been investigated from the ferroelectric hysteresis loops (P−E curves), at 50 kV/cm, covering a wide temperature range. The obtained results revealed a ferroelectric ceramic composition with suitable properties and strong potential to be used in multifunctional electronic devices based on pyroelectric sensors combined with high efficiency energy storage performance and solid-state refrigeration technologies.

Electrical characteristics of in situ Mg-doped β-Ga2O3 current-blocking layer for vertical devices

The lack of p-type doping has impeded the development of vertical gallium oxide (Ga2O3) devices. Current blocking layers (CBLs) using implanted deep acceptors have been used to demonstrate vertical devices. This paper presents a pioneering demonstration of in situ Mg-doped β-Ga2O3 CBLs grown using metal–organic chemical vapor deposition. The Mg-doping density during growth was calibrated by quantitative secondary ion mass spectroscopy. Electrical test structures were designed with in situ Mg doped layers with various targeted Mg doping concentrations. The effectiveness of the CBL is characterized by using temperature-dependent current–voltage measurements using n-Mg-doped-n structures, providing crucial insight into the underlying mechanisms. Pulsed measurements show similar blocking characteristics as DC. To further validate the experimental results, a TCAD simulation is performed, and the electrically active effective doping is found to be dependent on the Mg-doping density, offering an alternate perspective on the optimization of CBL performance. Breakdown measurements show a peak 4 MV/cm field strength.

Different reverse leakage current transport mechanisms of planar Schottky barrier diodes(SBDs) on sapphire and GaN substrate

The effects of different substrates on the off-state leakage current in gallium nitride (GaN) planar diodes are experimentally demonstrated and studied by analyzing temperature-dependent current–voltage characteristics. The two devices exhibit different leakage mechanisms despite being subjected to the same process conditions. The device with a sapphire substrate shows a more intricate leakage mechanism, implying the presence of additional leakage channels compared to the device with free-standing substrates. The electrical leakage characteristics in the planar GaN-on-sapphire device (referred to as utemp-SBD) and GaN substrate device (referred to as usub-SBD) Schottky barrier diodes (SBD) can be described by two distinct processes as the reverse bias gradually increases: utemp-SBD go through the thermionic emission (TE), variable range hopping (VRH), Frenkel–Poole (FP) emission and space-charge-limited conduction (SCLC) model; The leakage conduction mechanism of usub-SBD include TE, VRH, and FP emission mechanisms. It is noteworthy that in device 1, there is a rapid increase in leakage current within the voltage range of −36 to −40 V, primarily driven by the SCLC mechanism. This effect arises due to the presence of intrinsic traps in GaN grown on a heterogeneous substrate. Additionally, in the voltage range of −7 to −50 V (348 K to 448 K), the leakage mechanism shifts from FP emission to the VRH model, possibly due to variations in the Schottky barrier height.This study provides an in-depth analysis of the leakage mechanisms observed on different substrates and offers valuable insights for the design of planar gate transistors to minimize or avoid the occurrence of leakage channels.

Investigation of temperature dependant current transport mechanism in Ag/In2O3/p-Si/Al heterojunction

Employing the pulsed laser ablation technique nano-crystalline thin films of Indium oxide (In2O3) are deposited successfully on boron doped silicon substrate. The structural and morphological parameters of the films are investigated by using X-ray diffraction and atomic force microscopic (AFM) spectroscopy, respectively. The deposited films are the crystalline nanostructures with (400) as preferred diffraction peak and grain size of 56.56 nm approximately. The computed roughness (Rq) of In2O3 film is 1.02 nm. The AFM analysis validated the deposition of homogeneous smooth In2O3 films with surface roughness of the order of nanometer. UV–vis spectroscopy was used to study the optical properties of the films. Greater than 80% transparency in visible region was exhibited by the films. The value of the optical band gap was found to be 3.89 eV. The electrical parameters dominating the mechanism of current transport in n-In2O3/p-Si heterojunction were explored by observing the temperature-dependent current–voltage (I–V) properties. In the temperature range of 80–300 K, the ideality factor and barrier height were found to be strongly temperature dependent. It was noticed that with the decrease in temperature there is increase in ideality factor whereas decrease in barrier height which confirm the interfacial imperfections and inhomogeniety in potential barrier height distributions. The temperature dependence of I–V data has revealed the existence of double Gaussian distribution of barrier heights with mean values of 0.85eV and 0.78eV with standard deviation of 0.014 V and 0.012 V respectively. The modified Richardson's plot gives the average barrier height and Richardson's coefficient as 0.86eV and 4.7 × 105 Am−2K−2 in the temperature range 300 K–180 K and 0.77eV and 5.2 × 105 Am−2K−2, respectively in the temperature range 160 K–80 K. The values of Richardson's constants are of the order of known theoretical value of 3.2 × 105 Am−2 K−2.

Temperature sensor based on Sn2P2S6 crystal

Sn2P2S6, Sn2P2(Se0.05S0.95)6 and Sn2P2Se6 crystals are resistant to water, weak chemical aggressive media, and magnetic field. Model of low-temperature sensors is suggested, based on temperature dependences of the ac current.

Improved direct current electrical properties of XLPE modified by graftable antioxidant and crosslinking coagent at a wide temperature range

AbstractTo enhance the DC electrical performance of cross‐linked polyethylene (XLPE), the graftable antioxidant methacrylic acid 2‐hydroxy‐3‐(4‐anilinoanilino) propyl ester (GA), which contains carbonyl and amino groups, and the crosslinking coagent trimethylolpropane trimethacrylate (TMPTMA), which contains carbonyl groups, are individually or co‐grafted onto XLPE. The slightly higher deep trap density introduced by higher grafting concentration of TMPTMA results in more significant suppression effect of conductance current and enhanced breakdown strength at a lower temperature, while the suppression effect for the conductance current at 90°C becomes weakened due to limited trap energy. Meanwhile, the deeper energy level introduced by GA suppresses the conductance current and improves the electrical strength of XLPE at 90°C more significantly. By co‐grafting, the conductance current of XLPE in a wide range temperature can be significantly reduced, especially for the temperature dependence of conductance current, which is beneficial to suppress the field strength reversal. The results of thermally stimulated current and molecular simulation show that the polar groups of two monomers introduce deep charge traps in XLPE. The co‐grafting system ensures the rationality of the crosslinking reaction kinetics and does not affect the cable manufacturing.

Experimental Study on the Critical Current Properties of Flexible Nb3Al Superconducting Wires in Cryocooler System

In recent years, Jelly-rolled Nb/Al composite monofilament Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Al superconducting wires with an outer diameter of 30 μm, and multi-stranded Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Al wires were successfully fabricated by NIMS in Japan. So, it is necessary to measure the temperature dependence of the critical current of Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Al wires in cryocooler system for development of superconducting applications cooled by conduction cooling method. The single and multi-stranded ultrafine Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Al superconducting sample wires with different outer diameter were prepared to evaluate the critical current properties. The critical currents of sample wires were evaluated by the current sweep method and constant current method. In this study, the sample wires were soldered to the copper wire to prevent burnout of the sample wire during critical current measurements. Therefore, the amount of current shunted to the copper wire was estimated to accurately evaluate the critical current of the superconducting wire. Also, the critical current of Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Al wires due to bending strain (bending radius of 5 to 15 mm) was experimentally investigated. From the critical current measurement results of Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Al wires with different cross-sectional structures, it was confirmed that the superconducting properties of the wires were improved by reducing the wire diameter. It was shown that the critical current density of the developed Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Al wire is lower than that of REBCO wire, but higher than that of commercial NbTi and Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn wires.

Effect of Strand Damage in Nb3Sn Rutherford Cables on the Quench Propagation in Accelerator Magnets

Accelerator magnets employing Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn Rutherford cables are more susceptible to conductor degradation than Nb-Ti magnets. Recent measurements on a Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn accelerator magnet have revealed unexpected behaviour such as decaying voltages at constant current plateaus of V-I measurements, inverse ramp rate and temperature dependence of quench currents, and anomalous quench propagation measured by so-called quench antennas. Numerical modelling has shown that these anomalies can be explained by an inhomogeneous degradation in the Rutherford cable, in which a subset of strands is fully or partially degraded. In this paper, we study how this type of degradation can affect the early stages of quench propagation. With the aid of a network model, we show how quench antenna signals can be used to diagnose inhomogeneous conductor degradation in the Rutherford cable.

Electron and hole injection barriers between silicon substrate and RF magnetron sputtered In2O3 : Er films

In2O3 : Er films have been synthesized on silicon substrates by RF magnetron sputter deposition. The currents through the synthesized metal/oxide/semiconductor (MOS) structures (Si/In2O3 : Er/In-contact) have been measured for n and p type conductivity silicon substrates and described within the model of majority carrier thermoemission through the barrier, with bias voltage correction to the silicon potential drop. The electron and hole injection barriers between the silicon substrate and the film have been found to be 0.14 and 0.3 eV, respectively, by measuring the temperature dependence of the forward current at a low sub-barrier bias. The resulting low hole injection barrier is accounted for by the presence of defect state density spreading from the valence band edge into the In2O3 : Er band gap to form a hole conduction channel. The presence of defect state density in the In2O3 : Er band gap is confirmed by photoluminescence data in the respective energy range 1.55–3.0 eV. The band structure of the Si/In2O3 : Er heterojunction has been analyzed. The energy gap between the In2O3 : Er conduction band electrons and the band gap conduction channel holes has been estimated to be 1.56 eV.