Enhanced photodetection and a wider spectral range in the In2S3–ZnO 2D–3D heterojunction: combined optical absorption and enhanced carrier separation at the type-II heterojunction

Abstract

Highly efficient broadband photodetectors based on 2D metal chalcogenides have enchanted immeasurable research curiosity due to their tunable bandgap and unique electrical properties suitable for applications in optoelectronic nanodevices. In the present study, we fabricated photodetectors based on heterojunctions composed of 2D nanoflakes of indium sulfide (In₂S₃) and ZnO with the aim to enhance the photodetection spectral range. The fabricated 2D–3D heterostructure exhibited superior photodetection performance in terms of a high responsivity (R_λ), specific detectivity, and external quantum efficiency with a broader spectral response extending from the UV to visible region. It displayed a high responsivity value of 440 mA W⁻¹, specific detectivity of 10 × 10¹⁰ Jones, and external quantum efficiency of 330%. The experimentally measured optical absorption edge, work function, and valence band offset confirmed the formation of a type-II band alignment at the β-In₂S₃–ZnO interface, which promoted the charge-carrier separation. The present study presents a novel way of enhancing the photodetector properties by combining a well-known oxide semiconductor with a 2D material having tunable optical properties.