On-Nanowire Axial Heterojunction Design for High-Performance Photodetectors

We report the growth of high-quality CdS/CdS x Se1–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.