Scalable Van der Waals Two-Dimensional PtTe Layers Integrated onto Silicon for Efficient Near-to-Mid Infrared Photodetection.

In recent years, there has been increasing interest in leveraging two-dimensional (2D) van der Waals (vdW) crystals for infrared (IR) photodetection, exploiting their unusual optoelectrical properties. Some 2D vdW materials with small band gap energies such as graphene and black phosphorus have been explored as stand-alone IR responsive layers in photodetectors. However, the devices incorporating these IR-sensitive 2D layers often exhibited poor performances owing to their preparation issues such as limited scalability and air instability. Herein, we explored wafer-scale 2D platinum ditelluride (PtTe) layers for near-to-mid IR photodetection by directly growing them onto silicon (Si) wafers. 2D PtTe/Si heterojunctions exhibited wavelength- and intensity-dependent high photocurrents in a spectral range of ∼1-7 μm, significantly outperforming stand-alone 2D PtTe layers. The observed superiority is attributed to their excellent Schottky junction characteristics accompanying suppressed carrier recombination as well as optical absorbance competition between 2D PtTe layers and Si. The direct and scalable growth of 2D PtTe layers was further extended to demonstrate mechanically flexible IR photodetectors.