A high-speed photodiode may include a photodiode structure having a substrate, a light-absorbing layer and a light-directing layer that is deposited on a top surface of the photodiode structure and patterned to form a textured surface used to change the angle of incident light to increase a light path of the incident light when entering the photodiode structure. In one embodiment, the light-directing layer may include a plurality of polygon such as triangular projections to refract the incident light to increase the light path thereof when entering the photodiode structure. In another embodiment, a plurality of nanoscaled sub-triangular projections can patterned on both sides of each triangular projection to more effectively increase the light paths. In a further embodiment, porous materials can be used to form the light-directing layer.