New trends in the preparation of high-performance Au/B-Si photodetector by wet chemical etching: the effect of etching time

Black silicon (B-Si) is a modification of normal silicon that has expanded its applications to high-performance optoelectronic devices and highly efficient solar cells. The reduction in optical reflection of B-Si is a crucial advantage that enables its efficient and economical use in photovoltaic devices. In this study, we investigate the effect of etching time on the structural, optical, and optoelectronic properties of B-Si prepared by the wet chemical etching method. Increasing the etching time results in the growth of nanostructures and the formation of larger pyramid sizes. The root mean square of surface roughness of B-Si decreases as the etching time increases. The optical reflectivity of B-Si decreases significantly with an increase in etching time. The average surface optical reflectivity decreases from 0.81 to 0.31 as the etching time increases from 10 min to 30 min. Photoluminescence studies reveal that as the etching time increases to 30 min, the emission peak shifts to longer wavelengths (red shift). The current–voltage characteristics of the Au/B-Si Schottky contact reveal that the best junction properties were found for the sample prepared at 30 min, as its ideality factor and barrier height were 1.5 and 0.71 eV, respectively. The figures of merit of the Au/B-Si photodetectors show a strong dependence on the etching time. The photodetector prepared at a time of 30 min exhibits the best performance, with its responsivity, external quantum efficiency, and detectivity at 16.7 A/W, 46.2 × 10²%, and 2.14 × 10¹² Jones at 450 nm and a bias of − 5 V. The obtained values of the figures of merit open the door for the detection of very weak optical signal applications. The energy band diagram of Au/B-Si photodetector as constructed under illumination.