Surface Engineered Hybrid Core–Shell Si‐Nanowires for Efficient and Stable Broadband Photodetectors

Silicon nanostructures have gained intensive interest to develop broadband photodetectors at a large‐scale due to their excellent electronic properties. Herein, Si‐nanowires (SiNWs) decorated with reduced graphene oxide:carbon quantum dots (rGO:CQDs) nanocomposite (NC), as core–shell heterojunction building blocks for broadband (ultraviolet (UV)–near infrared (NIR)) photodetectors (PDs), are demonstrated. The SiNWs and CQDs are synthesized by wet‐chemical etching and facile pyrolysis methods, respectively. Photogenerated carriers are transported through rGO because of its high electron mobility and favorable band alignment with CQDs and Si. Further, to minimize the recombination of photogenerated carriers, and enhance the response in the visible region, plasmon‐enhanced AuCQDs are incorporated in the shell matrix. The optimized heterostructure (rGO:AuCQDs/undoped CQDs/SiNWs) is sensitive to a broad wavelength range covering the UV to NIR (360 to 940 nm) region, manifests the excellent responsivity of 16 A W−1 at 360 nm, detectivity (D*) of 2.2 × 1013 Jones, and noise equivalent power as low as 2.8 fW Hz−1/2. The optimized PDs heterostructure demonstrates excellent air‐stability after 8 days of illumination without any encapsulation or protective coating. The proposed simple, cost‐effective, and Si‐process‐line compatible fabrication of Si‐based PD device structure imposes a great promise for highly efficient and stable advanced futuristic optoelectronic devices. Broadband (360–940 nm) and stable photodetection is demonstrated in core–shell heterojunctions of Si‐nanowire core and a shell of undoped carbon quantum dots (UCQDs)/reduced graphene oxide:Au‐incorporated CQDs (rGO:AuCQDs). The UCQDs are used as effective buffer to passivate surface states on Si nanowires. Nanostructured AuCQDs promote optical absorption in UV–vis excitation and rGO ensures transport of photoexcited carriers resulting in broadband characteristics.