The invention relates to a photodiode, which can expand an absorption band of a light and finish detection from a visible light band to an infrared light band (400nm to 1350nm). The photodiode has relatively high responsiveness on two important bands of 0.8-0.9 microns and 1.1-1.35 microns. The photodiode structurally comprises a heavily doped N-type Si substrate with an opening, wherein a lightly doped N-type Si epitaxial layer, heavily doped P-type Si and a table structure are sequentially laminated on the N-type Si substrate; the table structure comprises an intrinsic Ge buffer layer and heavily doped P-type Ge thereon; and a silicon dioxide dielectric layer and a passivation layer are sequentially laminated on the table. A metal contact cathode VR is arranged on the back surface of the N-type Si substrate; a first metal contact anode VAF is arranged on the heavily doped P-type Si; a second metal contact anode VAS is arranged on the heavily doped P-type Ge; and an anti-reflection layer is arranged on the back surface of the lightly doped N-type Si epitaxial layer.