Thickness effect of 2D PdSe2 film on performance of PdSe2/Si heterostructure photodetectors.

Two-dimensional (2D) PdSe2 film has the characteristics of adjustable bandgap, high carrier mobility, and high stability. Photodetector (PD) based on 2D PdSe2 exhibits wide spectral self-driving features, demonstrating enormous potential in the field of optical detection. Here, we design and fabricate PdSe2/Si heterojunction PDs with various thicknesses of the PdSe2 films from 10 nm to 35 nm. Due to the enhancement of light absorption capacity and built-in electric field of heterojunction, the photodetector with thicker PdSe2 film can generate more photo-generated carriers and effectively separate them to form a large photocurrent, thus showing more excellent photodetection performance. The responsivity and specific detectivity of the PdSe2/Si PDs with 10 nm, 20 nm, and 35 nm PdSe2 films are 2.12 A W-1 and 6.72 × 109 Jones, 6.17 A W-1 and 1.95 × 1010 Jones, and 8.02 A W-1 and 2.54 × 1010 Jones, respectively (808 nm illumination). The PD with 35 nm PdSe2 film exhibits better performance than the other two PDs, with the rise/fall times of 15.8 µs/138.9 µs at f = 1 kHz and the cut-off frequency of 8.6 kHz. Furthermore, we demonstrate that the properties of PdSe2/Si PD array have excellent uniformity and stability at room temperature and shows potential for image sensing in the UV-Vis-NIR wavelength range.