Temperature Dependence Of Current Research Articles

Modeling of Both Arrhenius and Non-Arrhenius Temperature-Dependent Drain Current for Organic Thin-Film Transistors

To describe both Arrhenius and non-Arrhenius temperature-dependent drain currents for the organic thin-film transistors, the effective trapped carrier concentration expression is presented. Based on the expression, following the Shur and Hack's trap limited carrier conduction theory, the analytical drain current model is developed. The temperature-dependent trap states' density is presented to explain the origin of the effective trapped carrier concentration expression.

Heat Hunting in a Freezer: Direct Measurement of Quasiparticle Diffusion in Superconducting Nanowire

Propagation and relaxation of nonequilibrium quasiparticles in superconductors are fundamental for functioning of numerous nanoscale devices, enabling operation of some of them, and limiting the performance of others. The quasiparticles heated above lattice temperature may relax locally via phonon or photon-emission channels, or diffuse over appreciable distances in a nanostructure altering the functionality of their remote components. Tracing quasiparticles experimentally in real-time domain has remained a challenging task owing to their rapid dynamics. With electronic nanothermometry, based on probing of the temperature-dependent switching current of a superconducting nanobridge, we monitor heat pulse carried by a flux of nonequilibrium quasiparticles as it passes by our detector with a noise-equivalent temperature of 10 $\mathrm{mK}/\sqrt{N}$, where $N$ is the number of pulses probing the bridge (typically $N=10\phantom{\rule{0.1em}{0ex}}000$), and temporal resolution of a single nanosecond. The measurement provides the picture of quasiparticle diffusion in a superconducting aluminum strip and direct determination of the diffusion constant $D$ equal to 100 ${\mathrm{cm}}^{2}/$s with no energy dependence visible.

Photostimulated Near-Resonant Charge Transport over 60 nm in Carbon-Based Molecular Junctions.

The bias and temperature dependence of both dark and photoinduced currents in carbon-based molecular junctions were examined over a wide range of oligomeric layer thickness (d) values from 4 to 60 nm. The dark current density versus bias (JV) response of nitroazobenzene molecular junctions exhibits the exponential thickness dependence consistent with coherent tunneling when d < 5 nm, but becomes weakly dependent on d and temperature (T) for d = 15-60 nm. The photocurrent (PC) response is orders of magnitude higher than the dark current for the same d and bias, with very different curve shape and much earlier onset with bias. Although the dark and PC differed greatly in magnitude for d > 14 nm, they both exhibit near zero attenuation coefficients (β < 0.05 nm-1) and are activationless (Eact < 5 meV) below ∼200 K. For d > 14 nm, both dark and PC become electric field (E) dependent and exhibit approximate overlap of J versus E response for d = 14-60 nm. The value of ln J versus E1/2 is linear for both PC and dark current, with very different magnitudes and slopes. We propose an orbital mediated transport for PC, which involves sequential tunneling of photogenerated electrons and holes between frontier orbitals of adjacent, weakly interacting oligomeric subunits. Such transport is "bulk-limited", E dependent, and nearly activationless due to small tunneling barriers and short distances between adjacent molecular orbitals. In contrast, the dark current is activated and injection limited due to an interfacial energy barrier much larger than that for bulk transport in the junction interior. Rapid, low-barrier transport between orbitals in adjacent molecules should significantly extend the "range" of molecular electronics to >50 nm and avoid the usually strong temperature dependence observed in thicker organic films.

Temperature-dependent resistive switching for gold/poly(methyl methacrylate)/heavily doped p-type Si/indium devices by incorporating black phosphorus into poly(methyl methacrylate)

This study determines the effect of incorporating black phosphorus (BP) nanosheets into poly(methyl methacrylate) (PMMA) on resistive switching (RS) mechanisms using the temperature-dependent current–voltage characteristics of gold/PMMA:BP/heavily doped p-type Si (p+-Si)/indium devices. A gold/PMMA:BP/p+-Si/indium device exhibits RS behavior, but a gold/PMMA/p+-Si/indium device exhibits set/reset–free current–voltage characteristics. The current in gold/PMMA:BP/p+-Si/indium devices is limited by ohmic conduction, the space charge or filled trap. Incorporating BP into PMMA results in a significant increase in the trap density for a PMMA:BP film, which increases the RS performance for gold/PMMA:BP/p+-Si/indium devices.

Automation Software for Semiconductor Research Laboratories: Measurement System and Instrument Control Program (SeCLaS-IC)

Metal–semiconductor (MS) contacts are main aspects of almost all electronic circuit elements. Thus, contact mechanism and its electrical properties to develop a faster and more reliable electronic device should be known. The electrical characterization of MS devices (in terms of temperature-dependent and/or independent current–voltage (I–V), capacitance–voltage (C–V) and capacitance–frequency (C–f) measurements) is applied frequently in methods for determining the electrical properties and how it works and what the possible applications are. We prepared a program for basic electrical measurements and parameter extraction from these measurements of MS contacts. It is important to prepare and use such a program for a research laboratory, because electrical measurements must be made quickly after the production process and users should be able to carry out this process easily. This work can be discussed in two separate sections. The first section consists of a measurement system, automated instrument control program and data acquisition program (SeCLaS-IC Semiconductors Laboratory Software—instrument control). The second section is data evaluation and basic electrical parameter extraction program (SeCLaS-PC Semiconductors Laboratory Software—parameter calculation). In this paper, we discussed temperature-dependent current–voltage (I–V–T), capacitance–voltage (C–V–T) and capacitance–frequency (C–V–f) measurement system and instrument control program. This system is comprised of controlling program, liquid nitrogen (LN2)-cooled handmade cryostat system, temperature measurement system, and Keysight B2912A Precision Source/Measure Unit (SMU) and Keysight E4980A Precision LCR Meter. All programs were developed using Keysight VEE Pro (Visual Engineering Environment) software (Formerly Agilent VEE Pro).

Photoresponse of current-biased superconductor/normal metal strip with large ratio of resistivities

We study the perspective of thin bilayer strips made of highly resistive (in the normal state) superconductor (S) and low resistive normal metal (N) as a detector of electromagnetic radiation. A small minigap in the quasiparticle spectra, induced in the N layer due to proximity induced superconductivity from the S layer and the ability of low resistive N layer to carry a larger superconducting current than the host dirty superconductor leads to steep temperature dependence of critical current of SN strip in wide temperature ranges. It results in higher sensitivity of current-biased SN strip to the electromagnetic radiation in comparison with S strip. We present experimental results on several microns wide MoN/Cu and MoN strips, which confirm this statement in the bolometric regime. We also discuss possible advantages of single photon counting by narrow SN strips.

TRANZYSTOROWY UKŁAD DO POMIARU TEMPERATURY

W artykule zostały przedstawione schematy miernika temperatury opartego na strukturach tranzystorowych. Została przeanalizowana zależność prądu kolektora od temperatury bez i przy zastosowaniu linearyzacji funkcji przetwarzania. Zaproponowano metodę linearyzacji opartą na formowaniu prądu kompensacyjnego, która pozwoliła zmniejszyć błąd pomiaru temperatury do ± 0,006°C w zakresach temperatury 40… 60°C i 60… 80°C oraz do ±0,08°C w zakresie 10… 90°C.

The Influence of Operating Temperature on the Performance of BIPV Modules

To investigate the effect of the operating temperature on the performance of building integrated photovoltaic modules, two different crystalline silicon (c-Si) module types (glass/backsheet and glass/glass) with two different mounting configurations (ventilated and insulated) were installed in Canobbio, Switzerland and monitored over more than four years outdoors. The differences in the performance loss rates (PLRs) between module types and mounting configurations were determined by using the year-over-year methodology. The glass/backsheet module was markedly affected by the higher operating temperature: PLR changed from 0.01%/yr for ventilated to $-$ 0.42%/yr for insulated. However, the glass/glass module showed an opposite and unexpected trend: PLR changed from $-$ 0.10%/yr for ventilated to 0.26%/yr for insulated. Analysis of the IV curve parameters revealed that the decreased performance of the insulated glass/backsheet module was chiefly due to the loss in the fill factor with increased resistance; however, the gain in the short-circuit current ( I sc) was the main driver for the increased performance of the insulated glass/glass module. Real-world temperature coefficients were further examined and they were mostly found to be in line with the values measured indoors. Lower power–temperature and higher current–temperature dependence of the insulated glass/glass module, compared to the ventilated construction, supported the observed performance and current behavior of this module.

Gate-Leakage Current Mechanisms in Silicon Field-Effect Solar Cells

Field-effect solar cells (FESCs) are increasingly attractive for 2-D heterojunction solar cells and especially for gate-tunable Schottky-junction solar cells. A prerequisite for applying FESCs is that the gate-leakage (GL) power must be far less than the output power. However, the conduction mechanism of the GL current in a FESC has yet to be described clearly, thereby leading to excessive gate power consumption. In this work, the GL current mechanisms for a silicon FESC are extracted and analyzed using temperature-dependent current-voltage measurements under dark and illuminated conditions. It shows that the GL current for a FESC in the dark is dominated by both temperature-dependent Poole-Frenkel (P-F) emission and hopping conduction, whereas, under illumination changes to the temperature-independent space-charge-limited (SCL) current. Furthermore, whether the incident light power of 62.5, 100, or 125 mW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> is used, or the gate dielectric of SiO2 is replaced by HfO2, the dominant GL current mechanism is consistent. Finally, the trap energy level is approximately calculated as 0.38-0.72 eV based on a P-F emission analysis; the mean trap spacing of 0.01-0.18 nm and the activation energy of approximately 0.02 and 0.05 eV are extracted by a hopping conduction analysis. Meanwhile, a rigorous SCL conduction analysis provides a carrier mobility of 1.4 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-8</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ·V <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> ·s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> in SiO2 and 5.3 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-8</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ·V <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> ·s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> in HfO2.

An Extensive Study of the Electrical Conduction in HKUST-1 Single Crystals

Metal-Organic Frameworks (MOFs), which is three-dimensional (3-D) nanoporous materials composed of metal ions and organic ligands coordinated together, has recently attracted enormous attention as functional materials for electronic devices owing to their structural and functional flexibility in the design, as well as relatively high thermal stability [1, 2]. Although there are some reports so far that guest molecule doping drastically improves the electrical conduction of MOFs, e.g. the electrical conductivity of HKUST-1 (Cu3(btc)2) increases by infiltration of TCNQ, most of those experiments has been done using pellet or polycrystalline film samples [3, 4]. To extract an intrinsic electrical current conduction, avoiding the influences of grain boundaries and the residual stress introduced into the film due to the substrate mismatching, the use of single crystalline sample is essential. In this work, we investigated the dominant conduction mechanism of TCNQ-infiltrated bulk HKUST-1 single crystals which include much less grain boundaries and residual stress, by measuring the electrical conductivity as functions of a bias voltage, temperature, and pressure. Sub-mm sized HKUST-1 single crystals were fabricated and infiltrated with TCNQ using a saturated TCNQ/CH2Cl2 solution. The temperature dependence of DC current between 30 °C to 110 °C in the ambient shows that a current at 10 V decreases with increasing temperature down to undetectable value of less than 1 x 10-12 A, although the current value at 30 °C of around 1 x 10-6 A is similar to that of polycrystalline films [3]. We also confirmed that the temperature dependence of DC current for un-infiltrated HKUST-1 single crystals almost agrees with those of the TCNQ-infiltrated ones. Therefore, TCNQ infiltration is not effective in improving an electrical conductivity and the relatively high electrical conductivity at 30 °C is attributed to the presence of water absorbed by samples from the ambient, which was confirmed by thermogravimetric analysis. These results indicate that the current we measured was attributed to the ionic conduction probably due to the electrolysis of water inside the nanoporous structure not to the electronic conduction. Therefore, it is implied that the drastic improvement of the conductivity in the TCNQ-infiltrated HKUST-1 reported in ref. [3] is due to the use of film instead of bulk single crystal. It is suggested that the residual stress introduced into the HKUST-1 film by substrate mismatching plays a key role in the improved electronic conduction of the TCNQ-infiltrated HKUST-1 system. We will also discuss the effect of applying high pressure to the single crystals.

Statistical analysis of AC dielectric breakdown in transformer oil-based magnetic nanofluids

Insulating nanofluids often exhibit better insulating properties than their base liquids. In particular, dielectric breakdown performance of insulating liquids may be remarkably enhanced by the presence of nanoparticles. The purpose of this paper is to demonstrate experimental evidence of the missing enhancing effect of the magnetic nanoparticles dispersed in transformer oil and to find potential reasons for the unimproved AC dielectric breakdown. The research is conducted on a long-term stable magnetic nanofluid with three different volume fractions of iron oxide nanoparticles coated with oleic acid. The AC dielectric breakdown voltage is investigated at various temperatures and statistically treated. Temperature-dependent viscosity, dissipation factor, and AC electric current are presented as supporting experimental results. In searching for the reason of the unimproved dielectric breakdown, we focus on the nanoparticle interface and consider the limited ability of the modified nanoparticles to act as charge trapping centers under the AC dynamic conditions.

Evidence of Poole-frenkel and Fowler-Nordheim tunneling transport mechanisms in leakage current of (Pd/Au)/Al0.22Ga0.78N/GaN heterostructures

In this report, the gate leakage mechanism for AlGaN/GaN high electron mobility transistors (HEMTs) is consistently analyzed by means of temperature-dependent reverse gate current–voltage characteristics in the temperature range of 60–320 K. The gate leakage current of the AlGaN/GaN HEMT is studied by adjusting the experimental data using Poole–Frenkel (PF), and Fowler–Nordheim (FN) tunneling. In the temperature range of 200–325 K, the reverse bias leakage current is well dominated by a Frenkel-Poole emission model. The scenario describing the PF mechanism assumes that a defect level at φt = 0.45eV could be considered as an intermediate level through which carriers can transit to reach another level attributed to dislocations closer to conduction band. On the other hand, the FN mechanism seems to operate over the entire temperature range of 60–320 K and starts to dominate the gate leakage current due to triangular barrier formation.

Methods of Compensation for the Temperature Dependence of the Reference Voltage Sources of Integrated Circuits

The basic principles of reference voltage source construction are considered in the article. Possible sources of error of the output reference voltage, advantages and disadvantages of the existing architectural solutions of the reference voltage sources are analyzed. An architectural solution for the construction of a reference voltage source with higher order nonlinearities compensation is proposed, which has a temperature independent output voltage and is capable of operating at a supply voltage equal to or below 1 V. This solution has the possibility of implementing in the standard CMOS technology. Recommendations for compensation for the error caused by the offset voltage of the operational amplifier are given.In the modern world, integrated circuits (ICs) are the nucleus of virtually all electronic systems. When designing many ICs, one of the most important tasks is to generate accurate voltages for the entire circuit. The ICs that create these voltages are often referred to as the reference voltage sources. The reference voltage is a major component of both fully analog and digital circuits and even memory elements. There is a particular demand for low voltage power supplies as it is required for modern gadgets, mobile phones, laptops, cameras, etc. They should have low sensitivity to changes in power supply, possible deviations in the parameters of the manufacturing process and temperature.The reference voltage sources in standard CMOS technology have high precision output voltage, but temperature dependence is a problem. Another problem of such circuits is the inability to operate with a supply voltage below 1 V. The reasons for this are two: the principle of their operation is based on a bandgap of silicon equal to 1.25 V, which already exceeds 1 V of power; the second reason is that low voltage sources of reference voltage contain an operational amplifier, which should also operate at low power. In this case, low voltage power supply generators have poorer accuracy rates than classical implementation. Therefore, improving the characteristics of reference voltage sources while being able to operate at a supply voltage close to or below 1 V is a problem and requires a compromise solution.In the article was analyzed generators that provides proportional to absolute temperature (PTAT) voltage at their outputs, generators that provides complementary to absolute temperature (CTAT) voltage at their outputs. The source of the high-order nonlinearity was analyzed.The schematic of implementing reference voltage generators was proposed. The formulas for output voltage was derivated. The basic principles of operation of proposed schematic was described. The voltage reference, which utilizes the temperature-dependent currents generated from the parasitic n-p-n and p-n-p bipolar junction transistor devices in the CMOS process, is presented.

Control of Circular Photogalvanic Effect of Surface States in the Topological Insulator Bi2Te3 via Spin Injection.

The circular photogalvanic effect (CPGE) provides a method utilizing circularly polarized light to control spin photocurrent and will also lead to novel opto-spintronic devices. The CPGE of three-dimensional topological insulator Bi2Te3 with different substrates and thicknesses has been systematically investigated. It is found that the CPGE current can be dramatically tuned by adopting different substrates. The CPGE current of the Bi2Te3 films on Si substrates are more than two orders larger than that on SrTiO3 substrates when illuminated by 1064 nm light, which can be attributed to the modulation effect due to the spin injection from Si substrate to Bi2Te3 films, larger light absorption coefficient, and stronger inequivalence between the top and bottom surface states for Bi2Te3 films grown on Si substrates. The excitation power dependence of the CPGE current of Bi2Te3 films on Si substrates shows a saturation at high power especially for thicker samples, whereas that on SrTiO3 substrates almost linearly increases with excitation power. Temperature dependence of the CPGE current of Bi2Te3 films on Si substrates first increases and then decreases with decreasing temperature, whereas that on SrTiO3 substrates changes monotonously with temperature. These interesting phenomena of the CPGE current of Bi2Te3 films on Si substrates are related to the spin injection from Si substrates to Bi2Te3 films. Our work not only intrigues new physics but also provides a method to effectively manipulate the helicity-dependent photocurrent via spin injection.

Current Transport Mechanism in Palladium Schottky Contact on Si-Based Freestanding GaN

In this study, the charge transport mechanism of Pd/Si-based FS-GaN Schottky diodes was investigated. A temperature-dependent current–voltage analysis revealed that the I-V characteristics of the diodes show a good rectifying behavior with a large ratio of 103–105 at the forward to reverse current at ±1 V. The interface states and non-interacting point defect complex between the Pd metal and FS-GaN crystals induced the inhomogeneity of the barrier height and large ideality factors. Furthermore, we revealed that the electronic conduction of the devices prefers the thermionic field emission (TFE) transport, not the thermionic emission (TE) model, over the entire measurement conditions. The investigation on deep level transient spectroscopy (DLTS) suggests that non-interacting point-defect-driven tunneling influences the charge transport. This investigation about charge transport paves the way to achieving next-generation optoelectronic applications using Si-based FS-GaN Schottky diodes.

Charge Transport in Vertical GaN Schottky Barrier Diodes: A Refined Physical Model for Conductive Dislocations

Charge transport mechanisms of forward and reverse leakage currents in vertical GaN Schottky barrier diodes are investigated by measuring the temperature-dependent current–voltage characteristics. The results show that the leakage current is primarily governed by dislocation-associated thermionic field emission (TFE). The primary transport path is the reduced, localized conduction band around the dislocation core rather than the continuum defect states. A refined phenomenological physical model is developed for conductive dislocations in GaN, emphasizing that: 1) surface donors, surrounding the core of dislocations, can significantly shrink the barrier region after ionization, causing severe TFE leakage; 2) the $\text{O}_{N}$ donors likely to be responsible for TFE have a typical density of $\sim 1\,\,\!\times \! \,\,10^{{18}}$ cm $^{-{3}}$ at 300 K and activation energy of 78 meV; and 3) the barrier height at donor sites is ~0.65 eV at 300 K, which is reduced by ~0.4 eV with respect to the dislocation-free region.

Predictable quantum efficient detector for low optical flux measurements

The predictable quantum efficient detector (PQED) is a primary standard of optical power, which utilizes two custom-made induced-junction photodiodes that are mounted in a wedged trap configuration for the reduction of reflectance losses. PQED photodiodes of p-type and n-type were characterized for their dark current dependence on reverse bias voltage at room temperature. As simulations predict that the dark current will decrease exponentially with temperature, the temperature dependence of dark current for the n-type photodiodes was also measured. Two n-type induced-junction photodiodes were assembled inside a liquid nitrogen cryostat. The results from the dark current measurements indicate that the cooled n-type photodiodes are suitable for measuring optical fluxes in the few photon regime. A photon flux of approximately 7,000,000 photons per second was measured using the PQED at a cryogenic temperature with a relative standard uncertainty of 0.15%. The results support the utilization of the PQED as a primary standard of optical power in single and few photon applications.

AlInSb/InSb Heterostructures for IR Photodetectors Grown by Molecular-Beam Epitaxy

A photodetector heterostructure based on AlInSb/InSb was grown by molecular-beam epitaxy. Mesostructures of different diameters were fabricated. The temperature dependence of the dark current was measured. It was demonstrated that the built-in barrier blocks the flow of majority charge carriers, thus reducing the dark-current density (relative to that for a pin structure based on InSb). The measured dependence of the dark current on the mesostructure size revealed that the bulk current component prevails over the surface one.

Electron Transport across Vertical Silicon/MoS2/Graphene Heterostructures: Towards Efficient Emitter Diodes for Graphene Base Hot Electron Transistors.

Heterostructures comprising silicon, molybdenum disulfide (MoS2), and graphene are investigated with respect to the vertical current conduction mechanism. The measured current-voltage (I-V) characteristics exhibit temperature-dependent asymmetric current, indicating thermally activated charge carrier transport. The data are compared and fitted to a current transport model that confirms thermionic emission as the responsible transport mechanism across devices. Theoretical calculations in combination with the experimental data suggest that the heterojunction barrier from Si to MoS2 is linearly temperature-dependent for T = 200-300 K with a positive temperature coefficient. The temperature dependence may be attributed to a change in band gap difference between Si and MoS2, strain at the Si/MoS2 interface, or different electron effective masses in Si and MoS2, leading to a possible entropy change stemming from variation in density of states as electrons move from Si to MoS2. The low barrier formed between Si and MoS2 and the resultant thermionic emission demonstrated here make the present devices potential candidates as the emitter diode of graphene base hot electron transistors for future high-speed electronics.

Consistent Surface-Potential-Based Modeling of Drain and Gate Currents in AlGaN/GaN HEMTs

In this article, the gate current in AlGaN/GaN high-electron mobility transistors is modeled in a surface potential-based compact model. The thermionic emission, the Poole–Frenkel emission, and the Fowler–Nordheim tunneling are the dominant mechanisms for the gate current in the forward- and reverse-bias regions. These conduction mechanisms are modeled within the framework of the ASM-GaN compact model, which is a physics-based industry-standard model for GaN HEMTs, hence yielding a consistent model for the drain and gate currents. The proposed model captures the gate voltage, drain voltage, temperature, and gate-length dependencies of the gate current. The results of dc gate-leakage measurements of two GaN HEMT, differing only in terms of gate length, over a wide range of temperature, showing these current-conduction mechanisms, are presented, and the proposed model is validated accordingly. The developed gate current model, implemented in Verilog-A, is in excellent agreement with the experimental data.