We have measured the near-band-gap absorption of GaAs 1−x N x thin films with x Ͻ 0.012. The spectra were analyzed with a model which allows a precise determination of the band gap and of the width of the optical transitions; the latter is found to increase, for x Ͼ 0.002, well beyond what is expected in a III-V alloy. Ab initio calculations were performed within the generalized-gradient approximation with the exchange-correlation functional of Engel and Vosko [Phys. Rev. B 47, 13164 (1993)]. They reveal that the band gap depends markedly on nitrogen atomic configuration. The anomalous broadening of the intrinsic optical transitions thus gives strong evidence for configuration-induced band-gap fluctuations.

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Optical fi bressolar energy transmission and concentration provide a fl exible way of handling concentrated solar energy. Solar lighting with Fibre Optic Bundles (FOBs) can be considered a promising option for energy-effi cient green buildings. This study deals with the exergetic analysis and performance assessment of a system based on the idea of Transmission-Concentrated Solar Energy via Optical Fibres (TCSEvOF). A mathematical model is proposed for this study. The daily average exergy effi ciencies are found to be 27% for the spring and autumn equinoxes, it is expected that the presented model would be benefi cial to everyone involved in the design and performance evaluation of the solar lighting with FOB in building applications.

intense solar radiation and arid region in Algeria should be a promising issue to upgrade eco-friendly energy source alternative and promote climate change lute. For this purpose, we propose first principle investigation of the structural and the electronic bulk properties of the promising GaAsN alloy in delta-layer configuration within the aid of density functional theory framework. The simulation has been done to estimate the adequacy of this quantum design for optoelectronic and high efficiency photovoltaic applications. We particularly predict the evolution of the δ-layered Ga n As 1-n N 1 lattice constant for x=1/n in the range of 0