The Pd doped amorphous carbon (a-C:Pd) films were deposited on n-Si substrates with a native SiO2 layer using direct current magnetron sputtering. The dark and photo current–voltage (I–V) characteristics of the a-C:Pd/SiO2/Si were investigated. It is found that under white light illumination of 20 mW/cm2 at room temperature, the a-C:Pd/SiO2/Si fabricated at 350 °C has a large photoconductivity (the ratio of photocurrent to dark current) of 2000, which is much better than that of the a-C based junctions reported before. The large photoconductivity is attributed to the great increment of the reverse conductivity of the a-C:Pd/SiO2/Si under illumination, which is caused by the Pd doping.