A solution-fabricated tellurium/silicon mixed-dimensional van der Waals heterojunction for self-powered photodetectors

Abstract

Monoelemental two-dimensional (2D) tellurium (Te) has proved an excellent potential candidate for next-generation (opto)electronic devices due to its unique properties such as topological surface states, high carrier mobility, high light absorption coefficient, air stability, and flexibility. However, owing to a short photo-carrier lifetime brought by ultra-narrow bandgap and a large dark current brought by intrinsic high conductivity, Te-based photodetectors still suffer from limited performance, which severely impedes their further practical use in photodetection with low dissipation. In this study, we fabricated a p–n photodiode based on a 2D Te/Si mixed-dimensional van der Waals heterojunction (vdWH) constructed with well-designed type-I band alignment for high-performance near-infrared photodetection and polarized visible light-response under zero bias voltage. A strong built-in electric field across the p-Te and n-Si interface is introduced to suppress the dark current and accelerate the photo-generated carrier separation. As a result, a broadband sensitivity from 325 nm to 1064 nm light is exhibited. In particular, excellent self-powered performance with a low dark current of 2 pA, an ultrahigh I_light/I_dark ratio over 10⁵, a high responsivity (R) of 6.49 A W⁻¹, and a high specific detectivity (D*) of 7.79 × 10¹² Jones under 808 nm illumination can be achieved. Intriguingly, due to the in-plane low-symmetry atomic structure of Te nanosheets, it shows a linear polarization response with a photocurrent anisotropic ratio of 2.1 at 635 nm without any power supply. The above results prove that Te nanosheets are an ideal nanomaterial integrated with Si technology for high-performance and multifunctional optoelectronic systems in the future.