2D Bi2Se3–ZnO nanoparticle heterojunction based ultrafast photodetectors for enhanced detection in the UV to telecommunication wavelength

Abstract

The attractive properties of topological insulators (TI) have led to their consideration for various optoelectronic devices, including photodetectors. While ultrathin films of TI materials such as Bi₂Se₃ show good detection performance, the formation of a heterojunction with another compatible semiconductor can enhance detection metrics such as responsivity, detectivity, external quantum efficiency (EQE), response times, and others, besides broadening the wavelength range of photodetection. Here, we report a photodetector based on a 2D Bi₂Se₃–ZnO nanoparticle heterojunction for the first time, showing a one to three orders of magnitude improvement in the above metrics over the corresponding detectors using a single layer homojunction Bi₂Se₃. The active layer is first grown by a simple vapor phase synthesis, followed by spin coating of the ZnO nanoparticles, forming a Bi₂Se₃–ZnO type-I heterostructure. The built-in potential at the heterojunction interface greatly aids in the separation and transport of photogenerated carriers, resulting in a high responsivity of 22.13 AW⁻¹, high detectivity of 7.04 × 10¹² Jones and EQE of 6.77 × 10³% under 405 nm laser illumination and an ultrafast response with a rise time of 14.7 μs and fall time of 32.2 μs. Moreover, the detector shows a high responsivity of 2.89 mA W⁻¹, detectivity of 9.2 × 10⁸ Jones, and current on/off ratio of 1.06 × 10³ at self-bias operation (0 V). Finite element modeling reveals the role of ZnO nanoparticles in enhancing the electric field and light–matter interactions to obtain the observed photodetector performance. These impressive figures-of-merit represent a significant advance in the field of TI-based photodetectors. Furthermore, the photodetector demonstrates a broadband detection range from ultraviolet to optical telecommunication wavelengths. The TI-based Bi₂Se₃–ZnO nanoparticle heterostructure, with its simple architecture and low-cost fabrication, holds tremendous potential for high-performance electronic and optoelectronic applications.