Vertical MoTe₂/Ge Heterojunction Photodiode for 1550-nm Near-Infrared Photodetection

We demonstrate a vertical MoTe2/Ge heterojunction near-infrared photodiode that exhibits a low dark current density, an improved capacity of weak optical signal detection with a peak detectivity of $1.15\times 10^{{11}}$ Jones under a light density of 1 mW cm $^{-{2}}$ , and a response speed with a rise/fall time of 8/6 $\mu \text{s}$ operating at a 1550-nm light illumination. The device performance characteristics indicate that MoTe2/Ge heterojunction photodiode is promising for the potential practical application of photodetection at 1550 nm.