Magnetic Doping-Driven Tailoring of Photoresponse in Nanostructured Bi₂Se₃ Topological Insulator for Optoelectronics

The quest for cutting-edge materials with superior optoelectronic properties underscores the promise of topological insulators. The growth of the TI-based heterojunction enables the junction at the interfaces characterized by the strong built-in potential, significantly enhancing the photodetection performance. In this study, we report undoped and Cr-doped layered nanostructured Bi₂Se₃ heterojunctions exhibiting remarkable optical functionalities. Enhanced photocurrent and reduced dark current were observed with decreasing doping concentrations. Notably, the undoped Bi₂Se₃ displayed greater built-in potential which is mitigated in the Cr-doped Bi₂Se₃ owing to the alteration in carrier mobility and band structure alignment. To evaluate its potential applicability, photodetectors were fabricated utilizing undoped and Cr-doped Bi₂Se₃. The lowest Cr-doped Bi₂Se₃ exhibited the highest photoresponsivity of 19.6 A/W, whereas the undoped Bi₂Se₃ demonstrated superior performance, 37.1 A/W corresponding to a 1000 nm wavelength. The study presents an effective approach for developing ultrabroadband and high-performance devices, highlighting the potential of fabricated devices in advanced optoelectronic applications.