Mixed-dimensional vertical Bi2O2Se nanopillars/Si heterojunctions with the light confinement effect for high-performance photodetection

Bi2O2Se is considered to be a promising layered semiconductor material in the post-graphene era due to its high mobility, moderate bandgap, excellent air stability, and compatibility with current electronic industries. Heterojunctions based on Bi2O2Se, formed by introducing energy band-aligned heterogeneous semiconductor materials, exhibit significant potential for self-powered photodetection applications. However, currently all the reported Bi2O2Se-based heterojunctions are integrated in thin-layer configurations along Bi2O2Se's basal plane. Their photoelectric conversion performance is still limited by weak light absorption in thin-layer Bi2O2Se heterojunctions. To address this, we demonstrate a novel mixed-dimensional vertical Bi2O2Se nanopillars/Si heterojunction-based photodetector, achieved by depositing one-dimensional n-type Bi2O2Se nanopillars on three-dimensional p-type Si wafers via magnetron sputtering. The light confinement effect of the vertical Bi2O2Se nanopillars extends the light transmission path within Bi2O2Se, effectively mitigating the high reflectivity of planar silicon and the high transmittance of thin-layer Bi2O2Se, thereby enhancing the heterojunction's light absorption. The built-in electric field directed from n-type Bi2O2Se to p-type Si, combined with well-matched energy bands, facilitates the efficient separation of photogenerated electron-hole pairs, improving the photoelectric conversion efficiency and response speed of the heterojunction. The heterojunction photodetector exhibits self-powered characteristics, with a specific detectivity reaching 4.2 x 10(12) Jones and rapid rise/fall times of 24/40 mu s. Furthermore, the heterojunction photodetector demonstrates a broad spectral response, spanning from the ultraviolet to visible to near-infrared light region. Our work paves the way for the development of high-performance optoelectronic devices based on new-generation mixed-dimensional layered semiconductor materials.