The combination of photonics and silicon technology is a great challenge because of the potentiality of coupling electronics and optical functions on a single chip. Silicon nanocrystals are promising in various areas of photonics especially for light-emitting functionality and for photovoltaic cells. This review describes the recent achievements and remaining challenges of Si photonics with emphasis on the perspectives of Si nanoscale materials. Many of the results and properties can be simulated and understood based on theoretical studies. However, some of the key questions like the light-emitting mechanism are subjects of intense debates despite a remarkable progress in the recent years. Even more complex and important is to move the known experimental observations towards practical applications. The demonstrated devices and approaches are often too complex and/or have too low efficiency. However, the challenge to combine optical and electrical functions on a chip is very strong, and we expect more research activity in the field of Si nanophotonics in the future.

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Silicon Nanoscale Materials: From Theoretical Simulations to Photonic Applications

Solar cells in accordance with the present invention have reduced ohmic losses. These cells include photo-receptive regions that are doped less densely than adjacent selective emitter regions. The photo-receptive regions contain multiple four-sided pyramids that decrease the amount of light lost to the solar cell by reflection. The smaller doping density in the photo-receptive regions results in less blue light that is lost by electron-hole recombination. The higher doping density in the selective emitter region allows for better contacts with the metallic grid coupled to the multiple emitter regions. Preferably, the selective emitter and photo-receptive regions are both implanted using a narrow ion beam containing the dopants.

Solar cell fabrication with faceting and ion implantation

In recent years, silicon nanostructures have been investigated extensively for their potential use in photonic and photovoltaic applications. So far, for silicon quantum dots embedded in SiO2, control over inter-dot distance and size has only been observed in multiple bilayer stacks of silicon-rich oxides and silicon dioxide. In this work, for the first time the fabrication of spatially well-ordered Si quantum dots (QDs) in SiO2 is demonstrated, without using the multilayer approach. This ordered formation, confirmed with TEM micrographs, depends on the thickness of the initially deposited sub-stoichiometric silicon oxide film. Grazing incidence x-ray diffraction confirms the crystallinity of the 5 nm QDs while photoluminescence shows augmented bandgap values. Low-temperature current–voltage measurements demonstrate film thickness and order-dependent conduction mechanisms, showing the transition from temperature-dependent conduction in randomly placed dots to temperature-independent tunnelling for geometrically ordered nanocrystals. Contrary to expectations from dielectric materials, significant conduction and photocarrier generation have been observed in our Si QDs embedded in SiO2 demonstrating the possibility of forming initial film-thickness-controlled conductive films. This conduction via the silicon quantum dots in thick single layers is a promising result for integration into photovoltaic devices.

Film-thickness-dependent conduction in ordered Si quantum dot arrays

Solar cells and other semiconductor devices are fabricated more efficiently and for less cost using an implanted doping fabrication system. A system for implanting a semiconductor substrate includes an ion source (such as a single-species delivery module), an accelerator to generate from the ion source an ion beam having an energy of no more than 150 kV, and a beam director to expose the substrate to the beam. In one embodiment, the ion source is single-species delivery module that includes a single-gas delivery element and a single-ion source. Alternatively, the ion source is a plasma source used to generate a plasma beam. The system is used to fabricate solar cells having lightly doped photo-receptive regions and more highly doped grid lines. This structure reduces the formation of “dead layers” and improves the contact resistance, thereby increasing the efficiency of a solar cell.

Application specific implant system and method for use in solar cell fabrications

A system for processing substrates has a vacuum enclosure and a processing chamber situated to process wafers in a processing zone inside the vacuum enclosure. Two rail assemblies are provided, one on each side of the processing zone. Two chuck arrays ride, each on one of the rail assemblies, such that each is cantilevered on one rail assemblies and support a plurality of chucks. The rail assemblies are coupled to an elevation mechanism that places the rails in upper position for processing and at lower position for returning the chuck assemblies for loading new wafers. A pickup head assembly loads wafers from a conveyor onto the chuck assemblies. The pickup head has plurality of electrostatic chucks that pick up the wafers from the front side of the wafers. Cooling channels in the processing chucks are used to create air cushion to assist in aligning the wafers when delivered by the pickup head.

Substrate processing system and method

Plasma immersion ion implantation is an alternative doping technique for the formation of Ultra Shallow Junctions in semiconductor. In this study, we present the PIII technology developed by the company Ion Beam Services and called PULSION®. We explain the advantages of PIII for the conception of thin emitter solar cells and the use of N type silicon in the fabrication of photodiode. Electrical characterisations of solar cells prepared by immersion of silicon wafer in BF3 plasma are presented, showing a satisfying photovoltaic behaviour and more specially an increase of internal quantum efficiency in the short wavelength range, due to the thickness of the emitter.

Plasma Immersion Ion Implantation applied to P+N junction solar cells

SiO2 multilayers with embedded Si nanocrystals (Si-ncs) were investigated as an approach for developing highly efficient all Si tandem solar cells. The nanostructured samples, fabricated by means of a reactive magnetron sputtering, were structurally and optoelectronically characterized using different techniques. High resolution transmission electron microscopy (TEM) and energy filtered images in TEM show a high density of Si-nc with uniform sizes below 4 nm, while electrical characterization indicates high resistance values (102 kΩ) of these samples. In order to develop a better understanding of the optoelectronical behavior, photocurrent I-V curves were measured, obtaining variations under “dark” or “illumination” conditions. Recombination lifetimes in the order of tenths of nanoseconds were estimated by applying the transverse pump/probe technique.

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Structural and optoelectronical characterization of Si-SiO2/SiO2 multilayers with applications in all Si tandem solar cells

To achieve the requirements of the 45nm ITRS technology node and beyond, beamline implantation has reached its limit in terms of low energies. Plasma immersion ion implantation (PIII) is thus an alternative doping technique for the formation of ultrashallow junctions for source/drain extension in silicon devices. In this study, the authors present some results obtained on the PIII prototype called PULSION® designed by the IBS French company. In previous works [F. Torregrosa et al., Proceedings of the 14th International Conference on Ion Implant Technology, 2004 (unpublished); Proceedings of the 16th International Conference on Ion Implant Technology, 2006 (unpublished), p. 6], it has been shown that this machine offers the possibility to reach ultralow energy implantations and then to obtain implantation depths of only a few nanometers. One of the main issues is then to highly activate these junctions with a limited diffusion of dopants. Wafers have been implanted by PULSION® with acceleration voltages fr...

Realization of ultrashallow junctions by plasma immersion ion implantation and laser annealing

Selon un aspect, la presente description concerne un dispositif de detection de contamination surfacique par des particules evoluant en air libre. Il comprend une surface de collecte (10), fixe, destinee a recevoir des particules sur l'une de ses faces (11) et une tete optique (30) agencee du cote de la surface de collecte oppose a la face de reception (11) des particules. La tete optique un systeme optique imageur (38) pour la formation d'une image d'une surface d'analyse elementaire (13i) de la surface de collecte (10) sur une surface de detection (33) et une source d'eclairage (34, 35) permettant l'emission d'au moins un faisceau d'eclairage adapte pour recouvrir ladite surface d'analyse elementaire (13i). Des moyens de deplacement (40) de la tete optique (30) permettent un balayage selon les deux directions de la surface de collecte (10).

Procedes et dispositifs de detection de la contamination surfacique par des particules evoluant en air libre

A light source for injecting excess carriers into a semiconductor wafer, fully illuminating a surface of the wafer According to the disclosed embodiments, the source includes at least one set of point sources which are spaced apart at regular intervals along the X and Y axes, such that the source emits a monochromatic beam of a size that is at least equal to that of the semiconductor wafer surface to be illuminated Each of the point sources is sinusoidally modulated by a common electrical modulator, the distance between two point sources and the distance between the source and the semiconductor wafer surface to be illuminated being selected such that the monochromatic light beam uniformly illuminates the surface

Marcel Pasquinelli

Papers

Plasma Immersion Ion Implantation applied to P+N junction solar cells

Structural and optoelectronical characterization of Si-SiO2/SiO2 multilayers with applications in all Si tandem solar cells

Realization of ultrashallow junctions by plasma immersion ion implantation and laser annealing

Procedes et dispositifs de detection de la contamination surfacique par des particules evoluant en air libre

Electrically-modulatable extended light source and a measurement device for characterising a semiconductor including one such source