Bragg mirrors porous silicon back reflector for the light trapping in hydrogenated amorphous silicon

In this study we report on the photosensitivity of the electrical properties of a structure based on a thin film of hydrogenated amorphous silicon (a-Si:H) deposited onto a multilayer porous silicon (Bragg mirrors) formed in crystalline silicon (c-Si). We present the results obtained from dark and under illumination current-voltage (I-V) characteristics of Al/a-Si:H/PSi/c-Si structure. The aim of this study is to evaluate the influence of Bragg mirrors porous silicon at back-side on the electrical photosensitivity of a-Si:H. In this purpose, samples of monolayer and multilayer porous silicon have been formed in crystalline silicon by electrochemical etching method. The morphology and optical properties of monolayer samples have investigated by gravimetric analysis and reflectivity measurements, the Bragg mirrors are investigated by reflectivity measurements. The a-Si:H thin films were deposited by the DC magnetron sputtering technique in a mixture of argon and hydrogen atmosphere. These films were characterized by Fourier Transformed Infra Red spectroscopy and optical transmission. The I-V results obtained from dark show a decrease in current of Al/a-Si:H/PSi/c-Si structure compared with Al/a-Si:H/c-Si structure while there is enhancement of the photocurrent in the structure with Bragg mirrors back reflector. This result attests that the Bragg mirrors formed on crystalline silicon play an important role in the light trapping.