Evaluation Of Contact Resistance Research Articles

Effect Evaluation and Modeling of p-Type Contact and p-Well Sheet Resistance of SiC MOSFET with Respect to Switching Characteristics

SiC metal-oxide-semiconductor field-effect transistors (MOSFETs) exhibit excellent high-speed switching characteristics. However, the sheet resistance of the p-body region and the contact resistance between the p-body region and source electrode significantly degrade the switching performance. In this study, to clarify the effect of resistance on switching speed, which has not been sufficiently explored before, we used the temperature dependence of sheet and contact resistance and conducted switching tests under different temperature conditions. Furthermore, we created a circuit model that considered body effects and compared the results of the models with the measurements. We were able to reproduce the same temperature and resistance dependences as those exhibited by the experimental results, thus confirming the effectiveness of the model.

Analytical modeling of contact resistance and recombination for silicon heterojunction solar cells using hybrid carrier selective passivating contacts

Abstract Silicon heterojunction solar cells using Carrier Selective Passivating Contacts (CSPC) are the potential contenders for high efficiency next generation photovoltaics. Besides numerical simulations, the mathematical analysis of parameters affecting the performance of these cells is gaining considerable attention. In this work, the factors affecting the selectivity of silicon heterojunction solar cell using Hybrid Carrier Selective Passivating Contacts (H-CSPC) are investigated. This includes the evaluation of contact resistance and recombinations in the device. The contact resistance is analyzed in terms of partial resistances wherein an equivalent resistance model for the cell using H-CSPC is devised and resistances are inspected using quasi fermi level collapse over the contacts. The selectivity of the cell at each contact is examined and the condition for maximum selectivity is derived. Further, the recombinations in different regions of the cell using H-CSPC are analyzed. The recombinations at the TiO2/c-Silicon interface strongly deteriorate the V oc of the cell which is quantified using an analytical model under interface defect constraints and the results obtained are compared with simulations.

Evaluation of thermal contact resistance of molten resin–mold interface during high-thermal-conductivity polyphenylene sulfide filling in injection molding

Evaluation of thermal contact resistance of molten resin–mold interface during high-thermal-conductivity polyphenylene sulfide filling in injection molding

Thermal contact resistance evaluation of a thermoelectric system by means of three I-V curves

To achieve a suitable performance in a thermoelectric (TE) device it is important to minimize the thermal contact resistances between the device external surfaces and the heat exchangers of the system (heat source and heat sink). Despite its relevance, there are not many methods available for the evaluation of the thermal contact resistance, and the existing ones typically employ complex setups. Here, we present a new method to determine the thermal contact resistance of a TE device thermally contacted to a heat sink and a heat source. The method is based on performing three current-voltage (I-V) curves at different system conditions under a small temperature difference. First, an I-V curve with a high voltage scan rate, which avoids the variation of the initial temperature difference, provides the ohmic resistance. A second I-V curve performed with a constant input heat power (or the device suspended) provides the TE resistance. Finally, a third I-V curve with a constant temperature difference between the heat exchangers allows obtaining the thermal contact resistance. Using this method, a thermal contact resistivity value of 3.57 × 10−4 m2KW−1 was obtained for a commercial Bi-Te TE module contacted with a heat source and a heat sink using thermal grease as thermal contact interface material, which is in good agreement with reported values. The new method is highly advantageous, since neither involves complex setups nor requires the measurement of heat fluxes. Moreover, it measures directly under operating conditions for small temperature differences.

Practical evaluation of electrical contact resistance of thermoelectric legs at high operation temperature

The evaluation of the electrical contact resistances of thermoelectric legs is important to predict the performance of thermoelectric modules. Thermoelectric modules can be divided into devices operating at high and low temperatures. In the former, the electrical contact resistance can change with temperature. However, many research groups have only analyzed the electrical contact resistance at mainly room temperature. In this study, an electrical contact resistance measurement system for thermoelectric legs of thermoelectric devices at high operating temperature (400 to 600 °C) is proposed, which provides a more accurate performance prediction. The measurement conditions are determined according to the amplitude and frequency of the current to minimize the measurement errors caused by the Peltier effect. Skutterudite thermoelectric legs with a Ti metallization layer are used to understand the specific contact resistance at high temperatures. Based on the obtained results, the thermoelectric module is analyzed through a simulation to investigate the power outputs with the specific contact resistances at both room and high operation temperatures.

Evaluation of Contact Thermal Resistance of Ag Paste under High Heat Flux Conditions

This study describes the evaluation of thermal contact resistance under high heat flux. Next-generation semiconductor devices have advantage, which are high voltage device, and can be used under very high temperature and high heat flux. The contact thermal resistance of TIM (Thermal Interface Material) used at high temperature, thus, should be evaluated. Ag paste is expected as TIM used at high temperature. In this study, the contact thermal resistance is experimentally evaluated by steady state method. The experimental apparatus has heat transfer surface of φ 20.0 mm, and applied contact pressure to the heat transfer surface is 0.09 MPa. The results show that the temperature gap between the heat transfer surfaces show complete different tendency before / after solidification of the Ag paste.

Reduction in contact resistance and structural evaluation of Al/Ti electrodes on Si-implanted GaN

We investigated the conditions of sample preparation for obtaining low contact resistance to Al/Ti electrode on n-GaN fabricated by Si implantation and analyzed its interface structure. In conditions of sample preparation showing the lowest resistance, we found that there is an AlN layer and not the generally believed TiN layer on the interface between the electrode and the GaN substrate. Silicon was implanted into GaN followed by annealing at 1200 °C to investigate the effects of surface carrier concentration on ohmic contact. Layers of Ti and Al were then deposited and annealed at 550–800 °C. In the sample annealed at 600 °C with a relatively high fluence of 5 × 1014 atoms/cm2, the sample displayed the lowest contact resistance of 1.2 × 10−7 Ωcm2. This indicates that the formation of a high concentration of impurities on the GaN surface, resulting from Si implantation effectively reduced the contact resistance of the Al/Ti electrode. Ti and Al were also deposited on un-implanted GaN substrates, and the resulting multilayer electrodes with different Al/Ti ratios were annealed at 550–900 °C to investigate the electrode structure and the detail structure of metal/semiconductor interface. The film compositions and the interfacial microstructures of the samples were analyzed by the Rutherford backscattering spectroscopy method, optical microscopy, high-resolution scanning electron microscopy (STEM), energy-dispersive X-ray spectroscopy (EDX), and electron energy loss spectroscopy (EELS). For samples with Al/Ti ratios of ∼4.2, the under part of electrode became rich in Al at annealing temperatures of 550–600 °C. On the basis of the STEM and EELS analysis, Ti was not present at immediately above the GaN substrate interface, whereas AlN (thickness = 1–2 nm) was present. The RBS-determined total amount of Ga was 5 × 1015 atoms/cm2, which corresponds to the amount of Ga in 1.1 nm of the GaN layer that is probably replaced by the AlN layer.

Highly Conductive, Strong, Thin, and Lightweight Graphite-Phenolic Resin Composite for Bipolar Plates in Proton Exchange Membrane Fuel Cells

Featuring high efficiency and power density, relatively low operating temperature (60-80°C), quiet operation, and environmental friendliness, proton exchange membrane fuel cells (PEMFCs) have become promising power sources for transportation, stationary, and portable applications (1, 2). Bipolar plate is a vital and multifunctional component in PEMFCs, accounting for 60-80% of fuel cell stack weight and 30-45% of stack cost (3). While conventional bipolar plate materials are graphite or metal, graphite-polymer composites have recently been investigated as bipolar plate materials to maximally utilize the electrical conductivity of graphite and the mechanical strength of polymers and to exploit the benefits of smaller size, lighter weight, easier fabrication, and reduced cost. In this study, different polymer composites for bipolar plates based on synthetic graphite (SG), natural graphite (NG), and expanded graphite (EG) at a fixed graphite to polymer weight ratio were prepared by compression molding and compared in terms of three main properties: flexural strength, flexural modulus, and in-plane electrical conductivity. Novolac phenolic resin was chosen to form the composite because of its low cost and easy processing. EG turned out to be the best candidate, exhibiting flexural strength of 109 MPa and flexural modulus of 24 GPa even with a high graphite loading of 80 wt% and a low plate thickness of 0.9 mm, as well as in-plane conductivity of 182 S/cm. The EG content was then varied in a range of 60-85 wt% to find out the optimal composite composition. After this, a sandwich structure of buckypaper-composite-buckypaper was created to probe the effects of adding buckypaper on the mechanical and electrical properties. In addition, carbon nanotubes (CNTs) were incorporated into the EG-novolac resin composite for the first time, to the best of our knowledge, at low concentration of 0.5-2 wt% in the hope of potential benefits through nanostructuring. Through-plane electrical conductivity and corrosion resistance were also assessed for the composites with MWNTs 0-2 wt%. Previous research efforts on through-plane conductivity measurement either involved use of a reference material (4, 5), or calculated the sample bulk resistance roughly by assuming that all the contact resistances were the same (6), or did not provide specific description capable of separated analysis of interfacial contact resistance and bulk resistance (7). Herein a modified approach is suggested for detailed and reliable evaluation of through-plane resistance and contact resistance. As to corrosion behavior studies, a majority of them concentrated on metallic plates, some emerged in recent years to delve into the corrosion stability of graphite composites (8, 9), while the field of corrosion characteristics of EG-based bipolar plates and the influence that CNTs would have on their corrosion properties remains unexplored. The present work thus aims to shed some light on this aspect as well.

A method for direct contact resistance evaluation in low voltage coplanar organic field-effect transistors

In this paper, a method for the extrapolation of contact resistance in organic field-effect transistors (OFETs) from a single transfer characteristic curve in the linear regime is proposed. The method, namely DIrect Contact Resistance Extrapolation (DICRE), is based on the idea of making the current dependent only on contact resistance by setting the device in large over-threshold conditions. Constant contact resistance with respect to gate-to-source voltage is considered as an acceptable approximation, as confirmed by other examples in the literature. The effectiveness of the method is demonstrated by extrapolating the contact resistance of two different OFET structures (self-aligned and not self-aligned) and comparing the results with standard reference techniques, namely the Modified Transmission Line Method (M-TLM) and the Y function method. The results demonstrate that the DICRE method can be applied to low voltage devices without any damage to the gate insulator, even if the applied gate-to-source voltage drop is well beyond the values normally employed for transistor operation. The proposed method allows extrapolating a value of contact resistance comparable with the ones derived by TLM, with restrained variability. Moreover, the capability of properly recognizing the differences in contact resistance values between OFET structures with different features in terms of source/drain-gate overlap is reported. Finally, the possibility of correctly deriving the contact resistance dependence on drain-to-source voltage using DICRE is discussed.

Direct Contact Resistance Evaluation of Thermoelectric Legs

In developing intermediate temperature (300–700 °C) thermoelectric modules with high conversion efficiencies exceeding 10 %, the evaluation of the electrical contact resistance between the thermoelectric material and metallic electrode is a critical issue. In this work, a novel direct contact resistance measurement apparatus is proposed that enhances the previously reported extrapolation based erroneous contact resistance evaluation methods. The accuracy and resolution of this apparatus are investigated in detail, and the proposed novel contact resistance measurement exhibits sufficient performance to evaluate high efficiency thermoelectric modules. The presence of the Peltier effect in the direct current-induced contact resistance measurements is verified experimentally using the proposed apparatus. Two modified measurement parameters, i.e., the pulse shape input current and heat dissipating metallic block, are proposed and their effects in suppressing the unintended Peltier effect are discussed in detail.

3-D thermal analysis and contact resistance evaluation of power cable joint

Aiming at the overheating problem of power cable joints, which is mainly caused by great contact resistance and unqualified installation, a 3-D electromagnetic-thermal model for power cable joint was set up, and a method was presented to deal with the influence on the thermal distribution of power cable joint caused by the contact resistance RJ. Example calculation was described in details, and the result shows that the cable conductor temperature along the axial direction exponentially decreases within the range of 2 m away from the cable joint center. The numerical results agreed with the analytical results and measured results within 5%. Then the influence rules of contact coefficient k, ambient temperature Tamb and load current I on cable joint thermal distribution were investigated. Finally, the piecewise functions of the cable temperature difference ΔT, k and I were developed to evaluate the RJ of the power cable joint by regression analysis, which can be used to evaluate whether a power cable joint is qualified or not, and the correlation coefficients are greater than 0.999. Results indicate that to ensure the lower conductor temperature of cable joint than that of cable body, the k should be less than 2.7, and the relative error between the proposed evaluation method and the simulation method is within 2%.

Distorted constriction contact resistance between clamped slabs

Purpose – The purpose of this paper is the more exact evaluation of distorted constriction contact resistance between two clamped slabs or thin films, having a bi-dimensional current lines structure. Design/methodology/approach – Mathematical modeling using conformal mappings. Findings – The influence of the tarnish film on the distorted constriction resistance is clarified and three new exact formulas are proposed for the distorted constriction resistance between clamped slabs with rectangular contact spot. Comparisons with early proposed formula for constriction resistance of slab narrowing and with finite element analysis results are presented. Research limitations/implications – The research is limited to direct current and homogeneous and isotropic media and the results can be extended at alternate current when the skin effect is negligible. Practical implications – Exact evaluation of 2D constriction contact resistance which appears in macro-scale contacts electrical equipment and in MEMS devices, particularly in crimp contacts. Originality/value – The proposed formulas are new, original, simple and exact.

On the mobility and contact resistance evaluation for transistors based on MoS2 or two-dimensional semiconducting atomic crystals

Contact resistance (Rc) can substantially obscure the extracted mobility based on standard transconductance or two-point conductance measurements of field-effect devices especially for low density of states materials such as MoS2 or similar atomic crystals. Currently, there exists a pressing need for a routine technique that can decouple mobility extraction from Rc. By combining experiments and analysis, we show that the Y-function method offers a robust route for evaluating the low-field mobility, threshold voltage and Rc even when the contact is a Schottky-barrier as is common in two-dimensional transistors. In addition, an independent modified transfer length method evaluation corroborates the Y-function analysis.

C212 3オメガ法を用いた接触熱抵抗評価によるナノ構造ビスマステルライド薄膜の熱電特性

C212 3オメガ法を用いた接触熱抵抗評価によるナノ構造ビスマステルライド薄膜の熱電特性

Modified transmission-line method for evaluation of the contact resistance: Effect of channel-length-dependent threshold voltage

A modified transmission-line method (TLM) for organic field-effect transistors (OFET) contact resistance extraction is proposed. It is shown that the standard TLM approach can provide even the apparent negative contact resistance due to assumption of linear channel-length-dependence of the channel resistance and constant threshold voltage. This can be corrected by the modified TLM, where effect of channel-length-dependent threshold voltage is included with taking into account the dielectric nature of the active layer of OFETs. Obtained results illustrate the need of the threshold voltage discussion for contact resistance evaluation and demonstrate modified TLM approach as more reliable extraction method.

Power transfer-length method for full biasing contact resistance evaluation of organic field-effect transistors

A development of the conventional transfer-length method (TLM) for organic transistors’ contact resistance evaluation is proposed. By adding the dissipated power in access resistance and in the channel, we found that TLM can be extended to the non-linear region, i.e., up to saturation regime, which is widely believed to be a barrier for TLM application now. To improve the extraction accuracy and stability, a modified TLM version is used for the operation at small gate voltages. This modified power TLM is applied to polymer and pentacene field-effect transistors and proved as a useful tool for the contact resistance evaluation as a function of gate and drain voltages from common current–voltage characterizations.

Thermal Analysis of a New Type Langmuir Probe Based on Numerical Simulation and Experimental Studies

A new design of Langmuir Probe (LP) used for diagnosing plasma in Tokamak has been reported in this work. The thermal state of LP is given by finite element analysis and an explanation of temperature variation based on the changes in heat flux are presented. The evaluation of thermal contact resistance at the interface of different materials are presented. A effective analytical method based on numerical calculation and experimental investigation has been developed for studying the heat transfer capability of LP. This method, is able to predict the inner thermal state of LP, thereby leading to optimize the design of LP. Excellent agreement between simulated results and calculated results figured out by ANSYS and experimental data, indicated the validity of this model. These results obtained are useful for developing the high-performance LP.

Direct evaluation of low-field mobility and access resistance in pentacene field-effect transistors

Organic field-effect transistors (OFETs) suffer from limitations such as low mobility of charge carriers and high access resistance. Direct and accurate evaluation of these quantities becomes crucial for understanding the OFETs properties. We introduce the Y function method (YFM) to pentacene OFETs. This method allows us to evaluate the low-field mobility without the access or contact resistance influence. The low-field mobility is shown to be more appropriate than the currently applied field-effect mobility for the OFETs’ performance evaluation. Its unique advantage is to directly suppress the contact resistance influence in individual transistors, although such contact resistance is a constant as compared to the widely accepted variable one with respect to the gate voltage. After a comparison in detail with the transmission-line method, the YFM proved to be a fast and precise alternative method for the contact resistance evaluation. At the same time, how the contact resistance affects the effective mobility and the field-effect mobility in organic transistors is also addressed.

817 固体表面間の接触熱抵抗評価 : うねりの影響に関する理論的検討(GS 熱工学IV)

817 固体表面間の接触熱抵抗評価 : うねりの影響に関する理論的検討(GS 熱工学IV)

Numerical and experimental study of the contact resistance for high copper alloys in force domain 1–100 N

High copper alloys were required by the industry to improve mechanical and electrical contact resistance for connecting device. This work addresses the electrical contact resistance law versus force in the range (1-100 N) for sphere/plan shapes. The designed samples are submitted to indentation (static contact) and insertion (sliding contact). Experimental power law of contact resistance versus forces was obtained where the law parameters are well related to electrical resistivity, Young modulus, yield stress... Previous analytical relationship R c = f(F c ) in the literature and finite element simulation code are used to discuss the origin and the validity of such practical power law. Nevertheless the analytic expression are found unsatisfactory, the numerical model gives some agreement with this previous experimental law. However better convergence between numerical and experimental data was obtained in indentation when the surface topography is considered. The obtained results are a useful tool to evolve compromise between the electrical and mechanical aspects for a high loading contact. The main statement is that numerical model including the real topography and roughness is robust so it can be used in different contact shape and complex design for contact resistance evaluation. Finally, depending on the hardness and the resistivity, these uncoated materials were found to act on fretting apparitions and its level.