On-Nanowire Axial Heterojunction Design for High-Performance Photodetectors

We report the growth of high-quality CdS/CdS_xSe_1-x axial heterostructure nanowires (NWHs) via a temperature-controlled chemical vapor deposition method. Microstructural characterizations revealed that these NWHs have a single-crystalline structure with abrupt heterojunctions. Local photoluminescence and mapping near the heterojunctions show only two separated narrow band-edge emission bands from the two different adjacent semiconductors, further demonstrating the high-quality of these heterostructures. Moreover, the photodetector based on the single NWH shows a performance (higher responsivity (1.18 × 10² A/W), faster response speed (rise ∼68 μs, decay ∼137 μs), higher I_on/I_off ratio (10⁵), higher EQE (3.1 × 10⁴ %), and broader detection range (350-650 nm)) at room temperature superior to that of photodetectors based on single band gap nanostructures. This work suggests a much simpler route to achieve superior NWHs for applications in optoelectronic devices.