Asymmetric Schottky Contacts Enhanced Two-Dimensional Heterojunctions for Self-Powered Broadband and Polarization-Sensitive Photodetection

Schottky junction photodetectors, which utilize metal–semiconductor contacts, have attracted considerable attention due to their low cost, simplified fabrication process, and rapid response time. These attributes render them highly promising for applications in self-powered photodetection. Nevertheless, the Fermi-level pinning effect at the interface, the existence of defect states, and the substantial reverse leakage current of back-to-back Schottky junctions in devices often lead to difficulties in achieving precise modulation of the Schottky barrier and suboptimal rectification performance. In this study, an enhanced Au/2H-MoTe₂/1T’-MoTe₂ heterojunction based on asymmetric Schottky contacts is proposed for constructing a self-powered broadband and polarization-sensitive photodetector. The incorporation of the van der Waals material 1T’-MoTe₂ mitigates the Fermi-level pinning effect, thereby significantly enhancing the rectification performance, with a rectification ratio exceeding 10⁴. Furthermore, the intrinsic in-plane anisotropy of 1T’-MoTe₂ endows the heterojunction with polarization photodetection capabilities. The wavelength-dependent photocurrent anisotropy ratio varies from 2.61 at 405 nm to 5.4 at 808 nm. More importantly, the presence of two codirectional built-in fields at the interface effectively extends both the photodetection range and overall performance. The heterojunction exhibits broadband response ranging from 405 to 2200 nm at zero bias. Under 660 nm laser irradiation, it demonstrates a peak On/Off ratio of 5.97 × 10⁴, a responsivity (R) of 80.59 mA/W, an external quantum efficiency (EQE) of 15.14%, and a specific detectivity (D*) of 1.05 × 10¹² Jones. This research not only demonstrates a high-performance and multifunctional self-powered photodetector but also offers valuable insights into the development of advanced photodetectors.