Series Resistance Components Research Articles

Modelling and Simulation of a Photovoltaic Cell for Green Instrumentation Technology

Some photons are absorbed at the p-n junction; therefore a solar module is made up of photons of various energy. To represent the electrical behaviour of a solar cell, a single diode equivalent model has been utilised. A current source connected to a diode, a shunt resistance, and a series resistance component is used to simulate a perfect solar cell. Due to variations in light intensity and temperature, the parameters of the solar cell fluctuate. The mathematical model of the solar cell is developed using parameters in this study, and the model is then simulated with Matlab/Simulink. Solar cells may be used to generate renewable energy, which can be used in green instrumentation.

Improved Analysis of Gridline TLM Pattern Including Effect of Uncontacted Gridlines

Contact resistivity ( ρc ) for silicon solar cells is often measured using a pseudo-TLM pattern of equally spaced gridlines, which is cut from the cell itself. In this measurement, the uncontacted (floating) gridlines between two contacted gridlines are usually assumed to be disconnected from the silicon sheet. Analysis of such TLM data yields an approximate value of ρc , which is reasonably accurate for LT / L > 1, but increasingly less accurate for LT / L x /AlO x or SiN x ) to contact a p+-poly (p-TOPCon) layer, an n+-poly (n-TOPCon) layer, or a p+-boron (p-diffused) layer. The improved TLM analysis gave ρc values of 3.51, 0.89, and 5.26 mΩ·cm2, respectively. Analysis of the n-TOPCon data is complicated by 2-D current flow across the tunneling oxide and into the n-substrate, with corresponding uncertainty. Expressions for converting ρc to a component of series resistance are also given. Additional calculations were carried out to determine ρc error with approximate TLM analysis. With assumed LT / L values of 1, 0.5, and 0.25, the errors are 3.7%, 41%, and 280%, respectively.

Assessment of Series Resistance Components of a Solar PV Module Depending on Its Temperature Under Real Operating Conditions

Among the physical parameters of the standard single diode model of a solar cell, series resistance is one of those that strongly affects its performance. Contradictory changes in series resistance depending on temperature were reported in the literature. Accurate measurements of I-V characteristics were taken under different real operating conditions at constant temperature and solar irradiance, using a high-performance I-V curve tracer. The experimental results were used to determine series resistance of a photovoltaic module using two extraction methods. Empirical laws of series resistance components depending on module operating temperature were cheeked. It emerges that of the seven series resistance components, only four essentially determine its value.

Nondestructive Contact Resistivity Measurements on Solar Cells Using the Circular Transmission Line Method

The contact resistivity ( $\rho _c$ ) of screen-printed contacts is a significant component of series resistance in industrial solar cells. Measuring $\rho _c$ with standard techniques, such as the transmission line method (TLM), requires that the custom printed test structures be isolated from the device. In this article, we present a method for measuring $\rho _c$ on solar cells using the circular TLM (cTLM), where the test structures are hidden within the busbars of the solar cell. This alleviates the need for the test structure to be isolated from the device, allowing for the fast and nondestructive measurement of $\rho _c$ without causing additional shading on the cell. These measurements are performed with a semiautomatic tool, the ContactSpot-PRO, used for the accurate and systematic measurement of the $\rho _c$ on the cTLM structures. Our results show that the cTLM technique compares well to the linear TLM technique on several samples fired through a range of temperatures. However, numerical models generated using Quokka3 and scanning electron microscopy images indicate that structural differences in screen-printed TLM and cTLM structures affect the actual contact resistivity of each pattern. The numerical models also show how nonuniform sheet resistance beneath and in-between the printed contacts can affect the measured $\rho _c$ when using both the TLM and cTLM.

Extraction of individual components of series resistance using TCAD simulations meeting the requirements of 2- and 3-dimensional carrier flow of IBC solar cells

The series resistance (RS) of a solar cell, that influences fill factor and thus efficiency, is usually decomposed into individual components for development of optimization strategies. In this contribution we introduce a method to extract Rs of each part of the solar cell from TCAD simulation using free energy loss analysis. This method is particularly relevant for modern cell concepts where only TCAD simulation describes correctly high injection phenomena in lowly doped wafers, and where 2- or 3-dimensional carrier flow occurs (PERC, PERT, IBC) invalidating the classical analytical models for Rs description. We compare the lumped RS value extracted from the FELA to the RS extracted from the Multiple Light Intensity Method (MLIM) for IBC solar cells with various geometries and wafer doping levels, with and without a front surface field, and show that it is quite accurate even when high injection phenomena induce a slight underestimation of RS.

Series resistance effect on time zero dielectrics breakdown characteristics of MOSCAP with ultra-thin EOT high-k/metal gate stacks**Project supported by the National High Technology Research and Development Program (863 Program) of China (No. SS2015AA010601), the National Natural Science Foundation of China (Nos. 61176091, 61306129), and the Opening Project of the Key Laboratory of Microelectronics Devices & Integrated Technology, Institute of Microelectronics,

The time zero dielectric breakdown characteristics of MOSCAP with ultra-thin EOT high-k metal gate stacks are studied. The TZDB results show an abnormal area dependence due to the series resistance effect. The series resistance components extracted from the Fowler–Nordheim tunneling relation are attributed to the spreading resistance due to the asymmetry electrodes. Based on a series model to eliminate the series resistance effect, an area acceleration dependence is obtained by correcting the TZDB results. The area dependence follows Poisson area scaling rules, which indicates that the mechanism of TZDB is the same as TDDB and could be considered as a trap generation process.

Outwitting the series resistance in scanning spreading resistance microscopy

The performance of nanoelectronics devices critically depends on the distribution of active dopants inside these structures. For this reason, dopant profiling has been defined as one of the major metrology challenges by the international technology roadmap of semiconductors. Scanning spreading resistance microscopy (SSRM) has evolved as one of the most viable approaches over the last decade due to its excellent spatial resolution, sensitivity and quantification accuracy. However, in case of advanced device architectures like fins and nanowires a proper measurement of the spreading resistance is often hampered by the increasing impact of parasitic series resistances (e.g. bulk series resistance) arising from the confined nature of the aforementioned structures. In order to overcome this limitation we report in this paper the development and implementation of a novel SSRM mode (fast Fourier transform-SSRM: FFT-SSRM) which essentially decouples the spreading resistance from parasitic series resistance components. We show that this can be achieved by a force modulation (leading to a modulated spreading resistance signal) in combination with a lock-in deconvolution concept. In this paper we first introduce the principle of operation of the technique. We discuss in detail the underlying physical mechanisms as well as the technical implementation on a state-of-the-art atomic force microscope (AFM). We demonstrate the performance of FFT-SSRM and its ability to remove substantial series resistance components in practice. Eventually, the possibility of decoupling the spreading resistance from the intrinsic probe resistance will be demonstrated and discussed.

Pd/Ta2O5/SiC Schottky-diode hydrogen sensors formed by using rapid thermal oxidation of Ta thin films

Pd/Ta2O5/SiC Schottky-diode hydrogen sensors were fabricated, and their hydrogen gas sensing performance was investigated at 573 K and 773 K. Interfacial Ta2O5 films of 120 nm in thickness were formed by using rapid thermal oxidation (RTO) of the sputtered Ta films on SiC. The crystallinity of the Ta and the Ta2O5 films were characterized by using X-ray diffraction (XRD). As-sputtered Ta films on 4H-SiC are composed of α-Ta (body-centered-cubic) and β-Ta (tetragonal), and α-Ta (110) is the dominant orientation. After RTO at 573 K, the Ta films are converted to β-Ta2O5 (orthorhombic). The diode sensors show high sensitivity to H2 even at the low H2 concentration of 500 ppm, and the voltage change of the sensor upon H2 exposure is proportional to the H2 concentration in the range of 500 ∼ 2000 ppm at 573 K. The response voltage ΔV is shown to arise mostly from the change in the series resistance component of the sensor upon H2 exposure; the main origin of that change is believed to be the Ta2O5 interfacial layer. The response time t90 of the sensor at 573 K was estimated to be approximately 8 s.

Silver Contact Grid: Inferred Contact Resistivity and Cost Minimization in 19% Silicon Solar Cells

The analysis of silicon solar cell contacts having an H-bar front grid pattern is extended by enabling the contact resistivity to be inferred from the measurement of total series resistance and the determination of six individual components of series resistance. Analysis of the contact system was completed for a representative 19% cell fabricated from a 156-mm pseudosquare p-Cz wafer using standard production processes, including phosphorus ion implantation, thermal oxide surface passivation, silicon nitride deposition, and screen-printing and firing of front silver gridlines and busbars, back silver soldering pads, and back aluminum contact. Gridline width was measured to be 80 μm after firing, with an average thickness of 7.4 μm and an effective resistivity of 4.7 μΩ·cm. Contact resistivity to the uniform 91 Ω/ <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\square$</tex></formula> emitter was inferred to be 5.3 mΩ·cm <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$^{2}$</tex></formula> from the total series resistance and its components. Using these values, gridline spacing was optimized for maximum efficiency (1.7 mm, 91 lines, 19.1%, $0.040/W) or minimum silver cost (2.1 mm, 74 lines, 19.0%, $0.038/W). The analysis methodology was further applied to examine the impact of gridline width and silver pricing on cell efficiency and incremental cost. Such analysis can serve as a guideline for future contact system designs when the cost of silver changes or when printing technology allows narrower lines.

A Study of Parasitic Series Resistance Components in In–Ga–Zn–Oxide (a-IGZO) Thin-Film Transistors

We extracted the effective channel length and parasitic series resistance in a-IGZO inverted-staggered etch-stop (ES) TFTs. When there is an overlap between the drain or source electrode and the FET channel, the resistance of the channel underneath the overlapping regions is very low compared with other channel region resistance. As a result, the effective channel length is smaller than the physical length. The aforementioned definition of effective channel length in terms of device geometric parameters seems to be specific for ES a-IGZO TFTs.

Analysis of series resistance of crystalline silicon solar cell with two-layer front metallization based on light-induced plating

Improving the front metallization quality of silicon solar cells should be a key to enhance cell performance. In this work, we investigated a two-layer metallization scheme involving light-induced plating (LIP) and tried to quantify its impact on the series resistance of the front grid metals and FFs on finished cells. To estimate the effect of LIP processing on a printed and fired seed layer, individual components of series resistance were measured before and after LIP processing. Among them, grid resistance and contact resistance were closely observed because of their large contribution to series resistance. To optimize the plating on the seed metal grid, the grid resistance of the two-layer metal grid structure was calculated as a function of cross section area of the plated layer. Contact resistivity of the grid before and after LIP processing was analyzed to understand the contact resistance reduction, as well. As a result, the efficiency of solar cells with 80 μm seed metal grid width increased by 0.3% absolute compared with conventional solar cells of 120 μm metal grid width. The total area of electrodes in conventional cells was 1800 mm 2 and electrodes area of LIP processed solar cells was 1400 mm 2. The efficiency gain was due to reduction of shadowing loss from 7.7% to 6.0% without the increase of resistance due to two-layer front metallization.

3D Analysis of the performances degradation caused by series resistance in concentrator solar cells

This paper deals with the modeling of series resistance components in silicon concentrator solar cells. The main components of the macroscopic series resistance are analyzed by means of one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) numerical simulations. It is shown that the contribution of the lateral current flux, flowing along the emitter region, and of the transverse current flux, flowing along the metal grid, cannot be neglected and, hence, the operation of solar cells subjected to high current densities cannot be described by simple one-dimensional models. The percentage weight of 2D and 3D components on the total value of the series resistance is evaluated and rules for the proper design of the cell geometries are given. An analysis of the effectiveness of the most popular methods for the extraction of the series resistance from the I–V curves of solar cells is also proposed.

Gate-Length-Dependent Strain Effect in n- and p-Channel FinFETs

This brief reports the experimentally measured strain effect on electron and hole transport in (110)-oriented FinFETs. To separate out the series-resistance component, the low drain-bias resistance is differentiated with respect to the gate voltage. It is found that the hole mobility is enhanced while the electron mobility reduced toward short-channel devices. This effect is attributed to the gate-length-dependent strain in FinFET device structures.

Explanation for the dark I–V curve of III–V concentrator solar cells

AbstractThe measurement of the dark I–V curve is one of the most straightforward methods for characterizing solar cells. Consequently, an accurate knowledge of its meaning is of high relevance for the comprehension and technological feedback of these devices. In this paper, an explanation of the dark I–V curve for concentrator III–V solar cells is presented using a 3D (three‐dimensional) model in order to provide a proper data fit that provides meaningful physical parameters that are also compatible and coherent with a data fit from illumination curves. The influence on the dark I–V curve of the most significant series resistance components of concentrator solar cells is also analysed concluding that only the vertical component as well as the front contact‐specific resistance can be assessable by means of this characterization method while both emitter and metal sheet resistances cannot be detected. For comparison purposes, the same experimental data have been fitted by means of a traditional two‐diode model showing that, although an accurate dark I–V curve fitting can be achieved, the extracted parameters are unable to reproduce illumination data since lumped models assume the same ohmic losses distribution for both dark and illumination conditions. Copyright © 2007 John Wiley &amp; Sons, Ltd.

Microinductive Signal Conditioning With Resonant Differential Filters: High-Sensitivity Biodetection Applications

Inductive-based devices integrated with Si technology for biodetection applications are characterized, using simple resonant differential filter configurations. This has allowed the corroboration of the viability of the proposed circuits, which are characterized by their very high simplicity, for microinductive signal conditioning in high-sensitivity sensor devices. The simulation of these simple circuits predicts sensitivities of the differential output voltage which can achieve values in the range of 0.1-1 V/nH, depending on the coil parameters. These very high-sensitivity values open the possibility for the experimental detection of extremely small inductance changes in the devices. For real microinductive devices, both series resistance and parasitic capacitive components contribute to the decrease of the differential circuit sensitivity. Nevertheless, measurements performed using micro-coils fabricated with relatively high series resistance and coupling parasitic effects have allowed detection of changes in the range of 2 nH. which are compatible with biodetection applications with estimated detection limits below the picomolarity range.

A method to determine the gate bias-dependent and gate bias-independent components of MOSFET series resistance from S-parameters

An S-parameter measurement-based procedure for the extraction of the bias dependent and bias independent components of the MOSFET series resistance is presented. The proposed procedure allows the direct and analytical determination of these components from measurements performed on a single device. The method is verified by achieving good agreement between simulated and experimental data for a 0.18-/spl mu/m channel-length MOSFET.

Evaluation of InGaP/InGaAs/Ge triple-junction solar cell and optimization of solar cell's structure focusing on series resistance for high-efficiency concentrator photovoltaic systems

The series resistance of an InGaP/InGaAs/Ge triple-junction solar cell was evaluated in detail. Series resistance components such as electrode resistance, tunnel junction resistance and lateral resistance between electrodes were estimated separately. The characteristics of the triple-junction solar cell under concentrated light were evaluated by equivalent circuit calculation with a simulation program with integrated circuit emphasis (SPICE). By equivalent circuit calculation, the optimization of cell designs was performed, focusing on series resistance and cell current in order to realize high-efficiency concentrator cells.

Advanced model and analysis of series resistance for CMOS scaling into nanometer regime. II. Quantitative analysis

Source/drain (S/D) series resistance components and device/process parameters contributing to series resistance are extensively analyzed using advanced model for future CMOS design and technology scaling into the nanometer regime. The total series resistance of a device is found to be very sensitive to the variations of the sidewall thickness, the doping concentration in the deep junction region, and the Schottky barrier height of the silicide contact. A prediction of series resistance trends with technology generation indicates that silicide-diffusion contact resistance and overlap resistance will be major components in the total series resistance of nanometer-scale CMOS transistors scaled according to the ITRS roadmap. The key factors for challenging scaling barriers related to parasitic resistance are quantitatively examined as a function of technology scaling and it is shown that the series resistance can be substantially reduced through controlling both the abruptness of the S/D junction profile and the silicide Schottky barrier engineering.

Nickel, Platinum and Zirconium Germanosilicide Contacts to Heavily Phosphorous Doped Silicon-Germanium Alloys for Advanced CMOS Source/Drain Junctions

ABSTRACTAs the MOSFET dimensions continue to shrink, source/drain contact resistance is emerging as the dominant component of the MOSFET parasitic series resistance. To meet the series resistance requirements of future MOSFETs, contact resistivity values near 10-8 ohm-cm2 are required. Selective Si1-xGex source/drain technology has been proposed as an alternative to ionimplantation to form the ultra-shallow junctions of future CMOS technology nodes. One of the key advantages of this technology is the smaller band gap of Si1-xGex, which provides a smaller contact barrier height, an essential requirement for reducing the contact resistivity. We have previously reported low-resistivity of Ni germanosilicide NiSi1-xGex and Pt germanosilicide PtSi1-xGex contacts to boron doped Si1-xGex alloys. In this work, Zr germanosilicide, Zr(Si1-xGex)2 was considered as an alternative material with a higher thermal stability than Ni and Pt germanosilicides. The contact resistivity values for different contact materials were measured using four-terminal Kelvin structures. The results from this work show that both Zr and Pt germanosilicides yield high contact resistivity values around 10-7 ohm-cm2. On the other hand Ni germanosilicide contacts can reach 10-8 ohm-cm2 with further improvements using a thin layer of Pt under Ni.

Influence of series resistance on guidelines for manufacture of concentrator p-on-n GaAs solar cells

This paper deals with the determination of the main factors influencing series resistance in p-on-n GaAs solar cells working at concentration levels of 1000 suns or higher. Prior to this analysis, a comparison between different front metal grid geometries is presented to show the strong influence that the front grid component of series resistance exerts on its global value. Once the inverted square grid geometry is selected, a detailed analysis of the different components of series resistance is carried out. For this purpose, a multidimensional optimisation of the whole GaAs solar cell (antireflecting coatings, series resistance and semiconductor structure) has been used for the first time. In order to orient the manufacture of very high concentrator GaAs solar cells, recommendations on the threshold values of solar cell size, specific p- and n-contact resistances, thickness of the front metal grid and both doping level and thickness of the substrate are formulated. Several traditional ideas on the influence of these parameters are questioned. Copyright © 2000 John Wiley & Sons, Ltd.