Ultrahigh Speed and Broadband Few-Layer MoTe2/Si 2D-3D Heterojunction-Based Photodiodes Fabricated by Pulsed Laser Deposition

2D transition metal dichalcogenides are promising candidates for high-performance photodetectors. However, the relatively low response speed as well as the complex transfer process hinders their wide applications. Herein, for the first time, the fabrication of a few-layer MoTe2/Si 2D-3D vertical heterojunction for high-speed and broadband photodiodes by a pulsed laser deposition technique is reported. Owing to the high junction quality, ultrathin MoTe2 film thickness, and unique vertical n-n heterojunction structure, the photodiode exhibits excellent device performance in terms of a high responsivity of 0.19 A W-1 and a large detectivity of 6.8 x 10(13) Jones. The device is also capable of detecting a broadband light with wavelength spanning from 300 to 1800 nm. More importantly, the device possesses an ultrahigh response speed up to 150 ns with a 3-dB electrical bandwidth approaching 0.12 GHz. This work paves the way toward the fabrication of novel 2D-3D heterojunctions for high-performance, ultrafast photodetectors.