Microwave photoinduced varactor on silicon substrate

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Angle-dependent ray tracing simulations of reflections on pyramidal textures for silicon solar cells

International audiencePyramidal textures are commonly used to reduce reflections from silicon solar cells and improve light absorption by light trapping. They are generally modelled or characterized under normal incidence. In this work, a monolayer 3D ray tracing program taking into account the polarisation of light have been developed, validated and used to compute the directional-hemispherical reflectance versus the azimuth and incidence angles for both regular upright pyramids and inverted ones, with (111) facets. Results are given for a wavelength of 0.7 µm. They show that this reflectance is not minimal at normal incidence but for an incidence angle near 20 • and that upright pyramids can have a lower hemispherical reflectance than inverted ones for incidence angles in the middle range. The bihemispherical reflectance is 19.6% for regular upright pyramids and 20.7% for inverted ones. The effect of the pyramids aspect ratio on the hemispherical reflectance at normal incidence is also studied. This reflectance decreases with the aspect ratio of both textures. Above an aspect ratio of 0.51, inverted pyramids have a lower hemispherical reflectance. But their bihemispherical reflectance is lower only for aspect ratios below 0.23

Propriétés electriques des transistors bipolaires à hétérojonction sur InP pour des applications optoélectroniques monolithiques

Les transistors bipolaires à hètèrojonction (TBHs) sur substrat InP sont des composants trés prometteurs pour la fabrication des circuits rapides à bas niveau de puissance dissipée. Ils trouvent des appliactions très attractives dans le domaine de l'optoélectronique integrée monolithique. Les résultats présentés dans ce travail démontrent que des InP/InGaAs opto-TBH de type guide d'onde, peuvent etre fabriqués avec un comportement preque idéal et un niveau du bruit aux basse fréquence très rèduit

Low frequency noise behaviour of InP/InGaAs heterojunction bipolar waveguide phototransistors

In this paper we report on both the DC and low frequency noise (LFN) properties of InP/InGaAs heterojunction bipolar phototransistors (HPTs) featuring waveguide type illumination. Both DC and LFN measurements demonstrate the good quality of these devices. In particular, they exhibit a 1/f noise figure-of-merit of 2.10-8 \u3bcm2, which is exceptionally very good in the field of the compound semiconductor HBTs, where values around 10-7 \u3bcm2 are usually reported