An In2Se3/Ge heterojunction is fabricated via molecular beam epitaxy. The p-n junction device features a broadened photosensitive spectrum ranging from a visible (VIS) to short-wave infrared (SWIR) region (400-1700 nm). Notably, self-powered high responsivity of 0.32 A/W@450 nm and 0.52 A/W@1550 nm, decent specific detectivity of 3.2 × 1011 Jones@450 nm, and 5.2 × 1011 Jones@1550 nm at zero bias are achieved. Moreover, our photodetector exhibits a fast response speed with a sub-millisecond response time. These results can be attributed to the high quality of the In2Se3-Ge interface. Benefiting from the superposable dual-band photoresponse, the potential of the device for encrypted optical communication has been demonstrated.