1,721,376 research outputs found
Experimental technique for the performance evaluation and optimization of 1/f noise spectrum investigation in electron devices
No full textIn this paper, a fast and systematic experimental technique is proposed, which is devoted to the performance evaluation of power spectral density non-parametric estimators, in the framework of 1/f-noise bias-varying investigation at the ports of semiconductor electron devices. The methodology, which allows to overcome the need both for cumbersome analytical computation of a-priori moments, and non-reliable and time-consuming conventional statistical inference, provides the performance of the estimator and related parameters under investigation from a single realization, by exploiting the frequency stationarity of non-parametric algorithms in the relative and asymptotical sense. The technique has been applied to the case-study of a power MOSFET, by considering Bartlett, Welch and circular Welch estimators and different time windows and data record segmentation strategies, in order to verify its capabilities and, in particular, to identify the optimal non-parametric estimation of 1/f noise spectrum. In addition, results obtained by means of conventional statistical inference are compared to the estimates provided by the technique proposed, to the aim of further experimental assessment
Development of an analytical mobility model for the simulation of ultra-thin single- and double-gate SOI MOSFETs
No full textNumerical Simulation and Experimental Characterization of Emitter Wrap through Solar Cells with Deep Grooved Base Contact (EWT-DGB)
No full textAbstractIn this work we present an Emitter Wrap Through cell with Deep Grooved Base contact (EWT-DGB), designed for both 1-sun and concentrating applications. The proposed approach, which consists in a deep grooved hole array composed by holes of two alternating doping type, allows both a reduction of the cell series resistance and an increase in collection efficiency also by using relatively thick substrates with low lifetime. The measured experimental data including dark J-V characteristics, figures of merit (FOMs) under illumination and external quantum efficiency (EQE) are compared to the results of 3-D drift-diffusion TCAD numerical simulations. Moreover, the impact of the hole spacing and of process-dependent physical parameters (interface defects) on FOMs is investigated by means of simulations
Simulation Study of Multi-wire front Contact Grids for Silicon Solar Cells
No full textMulti-wire (MW) front-contact schemes represent a promising alternative to standard H-pattern structure with ribbon busbar (BB) in silicon solar cells. In the case of MW schemes, busbar are replaced by copper wires. MW have been demonstrated to enhance the photo-generation with respect to a standard H-pattern structure with ribbon busbar when solar cells are encapsulated and assembled in modules. However, the influence of the geometrical and optical properties of the encapsulation layers as well as of wires on the optical effective shading is not exhaustively treated by the literature. In this work, we have performed electro-optical simulations of MW and BB based solar cells in order to calculate the effective optical shading factor, the enhancement of conversion efficiency and the saving of contact-paste, with respect to the BB design. Specifically, we have studied by means of a ray-tracing simulation tool the significant impact of the front contact grid geometry, of the encapsulation layer thickness and of the optical properties of the cell front interface on the effective optical shading. The calculated values of effective optical shading are used to determine the enhancement of the figures of merit and the paste saving with respect to the reference silver BB scheme. On the basis of our calculations the adoption of optimized MW designs may enhance the conversion efficiency up to 0.5 %(abs), allowing paste saving up to 50 mg per cell
Investigation of the p-GaN gate breakdown in forward-biased GaN-based power HEMTs
No full textIn this letter, we report a detailed experimental investigation of the time-dependent breakdown induced by forward gate stress in GaN-based power HEMTs with a p-type gate, controlled by a Schottky metal/p-GaN junction. When a high stress voltage is applied on the gate, a large voltage drop and an electric field occur in the depletion region of the p-GaN close to the metal interface, promoting the formation of a percolation path. We have investigated the mechanisms underlying the gate breakdown by adopting different stress conditions, analyzing the influence of the temperature, and investigating the activation energy of the traps. In addition, thanks to this approach, the device lifetime has been evaluated and an original empirical model, representing the relationship between the gate leakage current and the time to failure, has been proposed
Theoretical study of the impact of rear interface passivation on MWT silicon solar cells
No full textIn this study we analyze the impact of a rear point contact (RPC) scheme in metal wrap through (MWT) solar cells with passivated base by means of numerical simulations. We adopt a modeling methodology which avoids cpu and memory intensive simulations of the whole true three-dimensional solar cell. The proposed approach exploits simplified three-dimensional simulation in combination to the adoption of calibrated semi-empirical models to account for the RPC scheme in an effective way. The sensitivity of the main figures of merit of the complete MWT cell to geometrical and doping parameters such as substrate thickness, hole size as well as substrate resistivity is discussed. From our simulations we observe that the adoption of a passivated base enhances significantly the conversion efficiency. In particular, we calculate an increase of efficiency up to 1.07%abs1.07%abs with respect to MWT without RPC and up to 1.33%abs1.33%abs with respect to conventional front contact solar cells, depending upon the substrate resistivity and the substrate thickness. The optimum base contact fraction results within the range 3–5 % and it is higher in the case of lower substrate doping or larger holes
Analysis of the impact of geometrical and technological parameters on recombination losses in interdigitated back-contact solar cells
No full textThis paper presents a detailed analysis of the recombination losses in an interdigitated back-contact (IBC) solar cell by means of three-dimensional numerical simulation. In particular, we discuss about the influence of geometrical and technological parameters such as the bulk thickness, the emitter contact fraction and the passivation effectiveness of the gap region on the saturation current density and on the carrier collection efficiency at region and mechanism-wise level. Moreover, the simulation results in terms of main figures of merit of the solar cell are reported and discussed. The paper shows that, except for the parasitic resistive losses, the optimum contact fraction at the emitter and base strongly depends on the presence of physical competing mechanisms, such as the internal optical bottom reflectivity and the recombination losses at the passivated emitter and base. In addition, the study underlines the critical role played by the passivation properties of the gap region, which may potentially be detrimental in terms of Fill-Factor and conversion efficiency
Experimental characterization of low-frequency noise in power MOSFETs for defectiveness modelling and technology assessment
Full text linkIn this work we analyse the applicability of low-frequency (LF) noise measurement in order to study the defectiveness in the gate oxide of power MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors). To this purpose, we implement a low-noise experimental set-up, which is able to measure, in particular, the flicker ("1/f'') contribution to the drain noise current of the device under test, with high accuracy in terms of noise floor and the adequate bias system flexibility required by the application. First, we show how these measurements can be used to empirically detect the physical model and related compact expressions, which best describe the source of 1/f-like fluctuations in this type of devices. Then, according to the selected physical model, the defect density in the gate oxide is extracted. In order to validate the proposed methodology, experimental data are reported and discussed in the case of power U-MOSFETs
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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