Enhanced light trapping using plasmonic nanoparticles

International audiencePlasmonics is a new light trapping method used in photovoltaic (PV) solar cells. A significant enhancement of the scattered and absorbed incident light due to the use of silver nanoparticles (Ag-NPs) was observed, which yield to the exaltation of the electromagnetic field in the vicinity of these NPs. In this context, we investigate optically and morphologically the effect of the NPs size dependence on the localized surface plasmon resonance. Extinction, absorption and scattering cross sections are calculated using Mie theory

CABRERA SÁNCHEZ, AGUSTÍN Y FAMILIA [Material gráfico]

Copia digital. Madrid : Ministerio de Educación, Cultura y Deporte, 201

Donor behaviour of implanted hydrogen ions in silicon wafers

Symposium on Hydrogen in Semiconductors, San Francisco, CA, APR 13-14, 2004International audienceP type Czochralski (Cz) and float-zone (FZ) grown silicon wafers were investigated with doping levels of 5x10(14) and 2x10(15) cm(-3), respectively. Hydrogen ions are implanted at a dose of 2x10(16) cm(-2), at energies in the range 20 to 250 keV and are accumulated at depth R-p in the range 0.2 to 2.4 mum. After implantation the wafers are annealed between 350 and 600 degreesC for 30 min, under argon flow. It is found that a graduated n-p junction is formed, and after metallization a photovoltaic device is obtained, which works like a solar cell. SIMS analysis shows that, around R-p, hydrogen concentration achieves 10(21) cm(-3). I-V and C-V curves confirm the formation of a N-type layer in which the donor concentration is about 5x10(17) cm(-3). When the samples are annealed at temperatures higher than 550degreesC the counter-doping vanishes. The observed behaviour of hydrogen is irrespective of oxygen concentrations in the wafers as it occurs in Cz (oxygen rich) like in FZ (oxygen poor) wafers. If the wafers are ion implanted with helium at the same dose and energy no junction appears. It is concluded that the agglomeration of hydrogen in silicon after ion implantation at a dose exceeding 10(16) cm(-2) gives rise to the formation of shallow donors

Electrical characterisation of 4H-SiC epitaxial samples treated by hydrogen or helium

6th European Conference on Silicon Carbide and Related Materials, Newcastle upon Tyne, ENGLAND, SEP, 2006International audienceThis paper presents results of investigations about the influence of Hydrogen (introduced by annealing or plasma implantation), and Helium (ion implantation followed by a proper annealing for creating nanocavities) on the electrical properties of 4H-SiC n-type epitaxial samples. First, 4H-SiC epitaxial layers were hydrogenated either by annealing under H-2 ambient or by a RF plasma treatment. This last process took place before or after the deposition of Schottky contacts. Two different annealing temperatures were imposed (300 degrees and 400 degrees C), as well as two plasma hydrogen doses for the same low energy. An improvement of electrical characteristics (25 % increasing of the minority carrier diffusion length, lowering of ideality factor, better switching characteristic) is detected for samples annealed at 400 degrees C. The treatment of 4H-SiC surface in hydrogen plasma through Ni metal also increases the diffusion length, but not sufficiently to have an effect on IN characteristics. A second set of 4H-SiC epitaxial layers were secondly implanted with He+ ions at two distinct temperatures. An annealing at 1700 degrees C during 30 minutes under argon atmosphere was then carried out. C-V measurements revealed the presence of a high charge density zone around the nanocavities, containing fixed negative charges, opposite in sign to the donor atoms

Minority Carrier Lifetime Measurements in Specific Epitaxial 4H-SiC Layers by the Microwave Photoconductivity Decay

7th European Conference on Silicon Carbide and Related Materials, Barcelona, SPAIN, SEP 07-11, 2008International audienceWe report oil measurements of the minority carrier lifetime for different epitaxial 4H-SiC layers by using the microwave photoconductivity decay (mu-PCD) method. This is a non-contacting, non-destructive method very useful for the monitoring of recombination processes in semiconductor material, Distinct samples have been analyzed, giving different lifetime values. Transmittance and absorption spectra have also been carried out. The n-type layers, giving rise to a specific absorption peak near 470 nm, are not sensitive to optical excitation for the used wavelengths, as opposite to p-type layers whose lifetime values depend on thickness and doping

n-p junction formation in p-type silicon by hydrogen ion implantation

International audienceHydrogen ion implantations at an energy of 250keV and a dose of 3 x 10(16) cm(-2) were applied to float zone, Czochralski grown silicon wafers and to multicrystalline samples. It was found that after annealing at 350degreesC < T < 550degreesC for 1 h a n-p junction is formed and a photovoltaic behaviour is observed. Spectral responses show that the photocurrent in the near infrared part of the spectrum is comparable to that given by a standard silicon solar cell. The depth of the junction is about 2mum and C-V measurements show that the junction is graduated. Hydrogen plasma immersion leads to similar results. The conversion of p- to n-type silicon is explained by the formation of shallow donor levels associated to a high concentration of hydrogen. (C) 2002 Elsevier Science B.V. All rights reserved

Temperature dependent lifetime spectroscopy (TDLS) for the identification of metallic impurities

6th International Conference on Crystalline Silicon Photovoltaics (SiliconPV), CEA INES, Chambery, FRANCE, MAR 07-09, 2016International audienceThe paper is devoted to the identification of the metallic impurities in silicon wafers by using Temperature Dependent Lifetime Spectroscopy (TDLS). We consider the variation of all recombination mechanisms, intrinsic and extrinsic, to follow the variation of lifetime with the temperature. The extrinsic recombination mechanism is based on the standard Shockley-Read-Hall theory (SRH) [1], [2] and we simulated the variation of SRH lifetime for two impurities : gold and iron. The simulation results show that their SRH lifetime variations with the temperature are opposite and that the presence of a peak is characteristic of the impurity studied. Experimental measurements are displayed showing the identification of gold impurity by means of Phase-Shift TDLS (PS-TDLS) measurement. Thanks to these results, we demonstrate that PS-TDLS is an efficient method to identify gold and iron impurities at concentrations as low as 1.10(10)cm(-3) for a doping level of 1.10(15)cm(-3). (C) 2016 The Authors. Published by Elsevier Ltd

Electrical characterizations of hydrogenated 4H-SiC epitaxial samples

11th International Autumn Meeting on Gettering and Defect Engineering in Semiconductor Technology (GADEST 2005), Giens, FRANCE, SEP 25-30, 2005International audience4H-SiC epitaxial layers were hydrogenated by means of plasma treatment and annealing, aiming at passivating the surface by forming bonds with Si atoms. Ni/SiC Schottky contacts were processed, and investigated by electrical methods (I-V-T, C-V-T, EBIC, DLTS). The annealings were performed at two different temperatures (300 degrees C and 400 degrees C) in H-2 ambient. The Inductively Coupled Plasma (ICP) treatment was effected before and after the Schottky contact metallization, and two integrated hydrogen doses were imposed for the same low energy (500 eV/atom). Two deep levels were detected in the gap of the sample hydrogenated at the highest dose before contact deposition, similar to the double defect RD1/2 associated to the vacancy pair V-Si-V-C. No deep level was found on other plasma-hydrogenated samples, which electrical characteristics are the same than for virgin SiC. A slight improvement of electrical parameters (lowering of ideality factor, increasing of minority carrier diffusion length, better switching behaviour) was only measured on the sample annealed at 400 degrees C

Nickel and gold identification in p-type silicon through TDLS: a modeling study

International audienceIn Silicon, impurities introduce recombination centers and degrade the minority carrier lifetime. It is therefore important to identify the nature of these impurities through their characteristics: the capture cross section σ and the defect level Et. For this purpose, a study of the bulk lifetime of minority carriers can be carried out. The temperature dependence of the lifetime based on the Shockley-Read-Hall (SRH) statistic and related to recombination through defects is studied. Nickel and gold in p-type Si have been selected for the SRH lifetime modeling. The objective of the analysis is to carry out a study to evaluate gold and nickel identification prior to temperature-dependent lifetime measurements using the microwave phase-shift (μW-PS) technique. The μW-PS is derived from the PCD technique and is sensitive to lower impurity concentrations. It has been shown that both gold and nickel can be unambiguously identified from the calculated TDLS curves

Electrical characterisation of 4H-SiC epitaxial samples treated by hydrogen or helium

6th European Conference on Silicon Carbide and Related Materials, Newcastle upon Tyne, ENGLAND, SEP, 2006International audienceThis paper presents results of investigations about the influence of Hydrogen (introduced by annealing or plasma implantation), and Helium (ion implantation followed by a proper annealing for creating nanocavities) on the electrical properties of 4H-SiC n-type epitaxial samples. First, 4H-SiC epitaxial layers were hydrogenated either by annealing under H-2 ambient or by a RF plasma treatment. This last process took place before or after the deposition of Schottky contacts. Two different annealing temperatures were imposed (300 degrees and 400 degrees C), as well as two plasma hydrogen doses for the same low energy. An improvement of electrical characteristics (25 % increasing of the minority carrier diffusion length, lowering of ideality factor, better switching characteristic) is detected for samples annealed at 400 degrees C. The treatment of 4H-SiC surface in hydrogen plasma through Ni metal also increases the diffusion length, but not sufficiently to have an effect on IN characteristics. A second set of 4H-SiC epitaxial layers were secondly implanted with He+ ions at two distinct temperatures. An annealing at 1700 degrees C during 30 minutes under argon atmosphere was then carried out. C-V measurements revealed the presence of a high charge density zone around the nanocavities, containing fixed negative charges, opposite in sign to the donor atoms