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Sergio Sapienza

Bio: Sergio Sapienza is an academic researcher from University of Parma. The author has contributed to research in topics: Carrier lifetime & Etching (microfabrication). The author has an hindex of 1, co-authored 4 publications receiving 3 citations.

Papers
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Journal ArticleDOI
TL;DR: In this article, an experimental-simulation approach is presented to correlate the carrier lifetime measured by simple OCVD measurements versus temperature with the reverse recovery behavior of the body diode, that can be useful at the design stage of power converters.

4 citations

Journal ArticleDOI
TL;DR: A new sensor concept is proposed based on I-V curve analysis coupled with artificial vision inspection of a reference PV module to quantify and identify the type of dirt and its usefulness in the automatic scheduling of maintenance interventions in smart-grid PV modules is assessed.

3 citations

Journal ArticleDOI
TL;DR: In this article, the activation energy for the electrical activation of 1x1019 cm-3 and 1x1020 cm -3 ion implanted Al in 4H-SiC has been estimated.
Abstract: The activation energy for the electrical activation of 1x1019 cm-3 and of 1x1020 cm-3 ion implanted Al in 4H-SiC has been estimated. Ion implantation temperature and dose rate were in the range 430-500°C and around 1011 cm2s-1, respectively. Post implantation annealing temperatures varied between 1500 °C and 1950 °C. The annealing time per each annealing temperature was sufficiently long that the sheet resistance of the implanted layer could be equal to the stationary value at the applied annealing temperature. The Arrhenius plots of the room temperature sheet resistances with respect to the post implantation annealing temperatures featured an exponential trend for both the implanted Al concentrations. The activation energies of these plots are the activation energy for placing an implanted Al atom in a substitutional site, i.e. the electrical activation energy. Activation energies around 1 eV, equal within errors for the two implanted Al concentrations, were found.

3 citations

Journal ArticleDOI
TL;DR: In this article, the effect of circuit setup on the ambipolar lifetime is discussed and a method, originally developed for improving the estimate of low-level carrier lifetime in OCVD measurements, is used to correct the measured lifetime for this influence.
Abstract: The open-circuit voltage decay (OCVD) method is a well-known technique for conducting electrical measurements of carrier lifetime: the main advantages lie in the simple setup and the possibility of carrying out measurements in commercial devices without the need of removing the package, as for optical methods. Despite several researchers having reported carrier lifetimes measured by the OCVD method in different devices, there has been little discussion about the potential effect of the experimental setup on the obtained results. By comparing the outputs of the experimental measurements with those of numerical simulations, this study investigates the overlooked effect of the OCVD measurement setup on the former. Due to the growing importance of SiC-based devices, the analysis is applied to a 4H-SiC p-i-n diode. Two main points are addressed: 1) the effect of circuit setup on the ambipolar lifetime is discussed and a method, originally developed for improving the estimate of low-level carrier lifetime in OCVD measurements, is used to correct the measured lifetime for this influence; 2) the origin of the local minimum eventually appearing in the lifetime versus time curves is also investigated. It is found that the minimum can also be related to the time constant of the experimental setup, giving rise to doubts about the usual interpretation of this minimum as the minority carrier lifetime. A method is thus proposed to help discriminate between the two interpretations.

2 citations

Journal ArticleDOI
TL;DR: In this paper , the distribution of stress field on micro-machined structures was investigated by using μ-Raman spectroscopy, showing different stress distributions on strain gauge, single and double clamped beams.
Abstract: In this work, we investigate, by μ-Raman spectroscopy the distribution of stress field on a micro-machined structures. They were realized on a 3C-SiC substrate, grown on a Silicon On Insulator (SOI) wafer, after lithography and etching processes. Various structures, such as strain gauge, single and double clamped beams, were analyzed, showing different stress distributions. All the structures show an intense variation of stress close to the undercut region.

1 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, the microstructure, composition, as well as anti-oxidation performance of Al-doped SiC coatings with different preparation temperatures (1500-2100°C) were explored.

23 citations

Journal ArticleDOI
TL;DR: A combination of low roughness parameter and high correlation length identify the transition from ripples to jagged morphology.
Abstract: The root mean square (rms) surface roughness extracted from atomic force microscopy is widely employed to complement the characterisation of ion implantation processes in 4H-SiC. It is known that the protection of a carbon film eliminates or mitigates roughening of the SiC surface during postimplantation annealing. This study, based on a rich original data collection of Al+ ion implanted 4H-SiC samples, allows for a quantitative description of the surface morphology as a function of the annealing temperature and time and of the Al implanted concentration. With increasing thermal budget, the evolution from flat, to blurred with ripples, granular, and finally jagged surface, results in a monotonous increase in the root mean square roughness. Additional information is given by the trends of the roughness exponent and of the correlation length, extracted from the height-height correlation function, which account for the surface evolution below 1700°C and for the effect of the Al implanted concentration on the ripple size, respectively. A combination of low roughness parameter and high correlation length identify the transition from ripples to jagged morphology. LAY DESCRIPTION: Selective area doping is a key step in the fabrication of hexagonal Silicon Carbide (4H-SiC) power electronic devices. It is achieved by ion implantation followed by a high temperature postimplantation annealing to restore the lattice and electrically activate the dopants. Aluminium, the preferred p-type dopant, is electrically activated at temperature ranging between 1500°C and 2000°C. The time required to complete the activation process is longer the lower the annealing temperature, spanning between some minutes and hundreds of hours. During annealing, 4H-SiC wafers are encapsulated by a temperature-resistant carbon layer (C-cap) in order to avoid step bunching and reduce surface roughening. Nevertheless, surface modifications can occur at high temperature. For this reason, the characterisations of 4H-SiC doping processes report not only the electrical activation of the dopants, but also the root mean square surface roughness obtained at the end of the process. However, rms values can be scattered because technological parameters such as the heating system and the way to deposit and remove the C-cap can affect the final result as well as the process parameters. Furthermore, the C-cap resistance to long annealing has been proven only by electrical measurements, but the surface morphology has never been observed. This work presents a quantitative characterisation of the surface morphology of Al implanted 4H-SiC as a function of the annealing temperature, time and of the Al implanted concentration, independent of the heating system and of the C-cap technology. The produced sample collection allowed to correlate characteristic surface features with the corresponding quantities extracted from image analysis that can be more sensitive to process parameters than the sole rms. These findings can be used to enrich process optimisation tools.

7 citations

Journal ArticleDOI
TL;DR: In this article , the authors analyzed the carrier lifetime in a drift layer of 1.2 kV-class SiC p-n diodes to suppress bipolar degradation and showed that 1/e 2 lifetimes obtained from the as-received epiwafer were much longer than 7.2 ns, even after H + implantation, high-temperature annealing, or electron irradiation.

3 citations

Journal ArticleDOI
TL;DR: In this article, the effect of circuit setup on the ambipolar lifetime is discussed and a method, originally developed for improving the estimate of low-level carrier lifetime in OCVD measurements, is used to correct the measured lifetime for this influence.
Abstract: The open-circuit voltage decay (OCVD) method is a well-known technique for conducting electrical measurements of carrier lifetime: the main advantages lie in the simple setup and the possibility of carrying out measurements in commercial devices without the need of removing the package, as for optical methods. Despite several researchers having reported carrier lifetimes measured by the OCVD method in different devices, there has been little discussion about the potential effect of the experimental setup on the obtained results. By comparing the outputs of the experimental measurements with those of numerical simulations, this study investigates the overlooked effect of the OCVD measurement setup on the former. Due to the growing importance of SiC-based devices, the analysis is applied to a 4H-SiC p-i-n diode. Two main points are addressed: 1) the effect of circuit setup on the ambipolar lifetime is discussed and a method, originally developed for improving the estimate of low-level carrier lifetime in OCVD measurements, is used to correct the measured lifetime for this influence; 2) the origin of the local minimum eventually appearing in the lifetime versus time curves is also investigated. It is found that the minimum can also be related to the time constant of the experimental setup, giving rise to doubts about the usual interpretation of this minimum as the minority carrier lifetime. A method is thus proposed to help discriminate between the two interpretations.

2 citations

Journal ArticleDOI
TL;DR: In this paper , the impact of dust particles on the performance of solar panels was investigated and a modern cleaning technique for PV modules, which would save time because it could be operated away from the PV modules.
Abstract: Solar power plays a significant role in the contribution of energy worldwide. The performance of solar panels mainly depends upon geographical and environmental factors. Dust is an important well known ecological factor that significantly impacts the performance of solar panels in achieving the overall target of power production by renewable sources. Study about the performance of solar panels under the influence of dust particles becomes more effective when these are to be worked out in hot and dusty areas. The current goal of this review article is to provide the impact of dust particles on the performance of solar panels. To fulfil this goal, the researcher's contribution is updated in minor for 2015 to 2018 and signed for 2019 and 2020.The current authors of this review article also recommended the adoption of a modern cleaning technique for PV modules, which would save time because it could be operated away from the PV modules.

2 citations