Predictable quantum efficient detector based on n-type silicon photodiodes

The predictable quantum efficient detector (PQED) consists of two custom-made induced junction photodiodes that are mounted in a wedged trap configuration for the reduction of reflectance losses. Until now, all manufactured PQED photodiodes have been based on a structure where a SiO2 layer is thermally grown on top of p-type silicon substrate. In this paper, we present the design, manufacturing, modelling and characterization of a new type of PQED, where the photodiodes have an Al2O3 layer on top of n-type silicon substrate. Atomic layer deposition is used to deposit the layer to the desired thickness. Two sets of photodiodes with varying oxide thicknesses and substrate doping concentrations were fabricated. In order to predict recombination losses of charge carriers, a 3D model of the photodiode was built into Cogenda Genius semiconductor simulation software. It is important to note that a novel experimental method was developed to obtain values for the 3D model parameters. This makes the prediction of the PQED responsivity a completely autonomous process. Detectors were characterized for temperature dependence of dark current, spatial uniformity of responsivity, reflectance, linearity and absolute responsivity at the wavelengths of 488 nm and 532 nm. For both sets of photodiodes, the modelled and measured responsivities were generally in agreement within the measurement and modelling uncertainties of around 100 parts per million (ppm). There is, however, an indication that the modelled internal quantum deficiency may be underestimated by a similar amount. Moreover, the responsivities of the detectors were spatially uniform within 30 ppm peak-to-peak variation. The results obtained in this research indicate that the n-type induced junction photodiode is a very promising alternative to the existing p-type detectors, and thus give additional credibility to the concept of modelled quantum detector serving as a primary standard. Furthermore, the manufacturing of PQEDs is no longer dependent on the availability of a certain type of very lightly doped p-type silicon wafers.Peer reviewe

MESURES OPTIQUES POUR LA CARACTERISATION D’ECLAIRAGES A LED

International audienceNEOLUX, a French company specialized in the development of LED lightings, built a photometry laboratory for the complete characterization of luminaries. During the metrological evaluation process of its equipments, the measurement accuracy of portable spectroradiometers was studied by comparison with instruments from the French national metrology institute called “Laboratoire commun de métrologie LNE-Cnam”. Huge measurement differences were observed between the portable spectroradiometers.NEOLUX, société française spécialisée dans la conception d’éclairages à LED, s’est dotée d’un laboratoire de photométrie pour la caractérisation complète de luminaires. Dans le cadre de l’évaluation métrologique de ses équipements, l’exactitude de mesure de spectroradiomètres portatifs a été étudiée par comparaison à des équipements du Laboratoire Commun de Métrologie LNE-Cnam. D’importants écarts de mesures entre les spectroradiomètres portatifs ont été observés

A high resolution set up devoted to the measurement of the Bidirectional Reflectance Distribution Function around the specular peak, at LNE-CNAM

We see objects because they reflect light. This reflected light contains information that allows us not only identify the shape of the object but also its appearance. The overall appearance of an object is a combination of different visual attributes like gloss, texture, color or transparency, which are produced by the interaction between the object, the light falling upon it and the visual system [1]. Our interest in this article is to characterize the gloss of a surface. Our approach is the measurement of the Bidirectional Reflectance Distribution Function (BRDF) of the surface in, and around the specular direction, where the specular peak is located. For this, we developed a dedicated gonioreflectometer with a very high angular resolution. In this paper we present the equipment and measurements made on different surface

Realisation of the ITS-90 and thermodynamic temperature measurements above 960 °C using a monochromator-based radiance comparator

International audienceAt LNE-Cnam, the International Temperature Scale of 1990 (ITS-90) and thermodynamic temperature measurements above the silver point, are carried out with a radiance comparator. This instrument is, more generally, devoted to any radiance comparison in temperature range from the ambient to 3000 °C. The instrument developed in the early 1990s at LNE-Cnam has the advantage of being completely adjustable. Compared to compact radiation thermometers based on lenses and a narrow-band interference filter, the radiance comparator is only made of gold coated mirrors and a Czerny-Turner monochromator to select the spectral bandwidth. The instrument offers the possibility to tune the geometric extent and the slit scattering function. In return, the radiance comparator is a complex instrument that requires a complete and a regular characterisation at the highest level of accuracy. In the first part, this paper describes the instrument and its operating principle. In a second part, a complete study of the wavelength calibration, the slit scattering function, size of source effect, out-ofband transmittance, linearity and other main sources of uncertainty are presented and discussed. Their associated uncertainties are estimated separately and are grouped together to give an example of propagation of uncertainties when realising the ITS-90