Abstarct: In this research work, synthesis and characterization of silicon nanowires (SiNWs) were investigated for Au/Si Schottky photodiodes applications. For this purpose we have used two kinds of Si wafers: p-Si (100) 0.5 and 1-10 Ωcm; and n-Si (100) 0.22 Ωcm. SiNWs were fabricated through one-step mextal Assisted Chemical Etching (1-MACE) process in HF/ AgNO3/H2O2 aqueous solution. In the first step, the optimum concentration of AgNO3 for etching of p-Si wafers was determined. For this purpose, solutions with different AgNO3 concentrations (0.015 and 0.020 M) were used. The FESEM images confirmed the formation of ordered and uniform arrays of nanowires in the higher concentration of AgNO3 (i.e. 0.020 M). Then in continue, the effect of etching time on samples morphologies using FESEM and TEM images were examined. These results showed that with increasing the etching time the average lengths of the NWs are increased while their diameters are decreased. Also we found that mesoporous silicon nanowires (mp-SiNWs) were obtained only through the etching durations of 60 and 80 minutes. In studying the influence of substrate resistivity, the FESEM and TEM images indicated that with increasing the resistivity of Si wafers, the average lengths and diameters of NWs are increased while the porosity is decreased. According to SAED patterns, nanowires still preserved the single crystalline structure of the starting Si wafers. The reflectance spectra of the etched samples revealed their very low reflectance (less than 0.1%) in the visible range. Such a substantially low reflectance in visible up to near infrared range, which is not achievable with the conventional anti-reflecting coatings, is suitable for the Si-baxsed solar cell applications. Raman spectra of the samples indicated the red-shifted peak position. The downshifts are attributed to the formation of silicon nano-crystallites (SiNCs) within the NWs. Using photoluminescence (PL) measurements it was revealed that the corresponding spectra only appears in samples etched for 60 and 80 min in which the SiNCs are decorated on the sidewalls of the NWs. The fabricated photodiodes (Au/p-SiNWs/Al) were exposed to LED lamps with 463, 526 and 626 nm wavelengths (blue, green and red lights respectively). In dark conditions the I-V data of the samples showed rectifying behavior; and under illumination indicated considerable variations in electrical current in reverse bias condition. Also, I-t characterizations of the samples showed a fast response to the incident lights, while the highest photocurrent was achieved for the red light illumination. We found out that samples with etching duration of 80 min have the highest photo-response ratio among these samples. In n-Si (100) etched samples, at room temperature only the 80 minutes etched sample showed the formation of mp-SiNWs. Furthermore, the effect of etching solution temperature on the morphological properties of nanowires were investigated. The FESEM and TEM images showed that the lengths of NWs are increased by increasing etching temperature from room temperature to 50 and 75 ℃, but the diameter changes are slight. Also the SAED patterns indicated that the SiNWs prepared at room temperature (RT) have single crystal structure, while those prepared at higher temperatures have polycrystalline structure. In addition, the reflectance spectra of the samples showed a significant reduction after NWs formation on Si wafer. The Fabricated Schottky photodiodes (Au/n-SiNWs/Al) were exposed to blue, green and red LED lamps. In all samples, I-t characterizations showed fast response to the incident lights and the highest photocurrent was occurred for red illumination. We found out that sample prepared during 80 min etching at 50 ℃ has the highest photo-response ratio.