Broadband photodetectors based on topological insulator Bi2Se3 nanowire with enhanced performance by strain modulation effect

Abstract

Photoelectronic properties can be effectively modulated by external mechanical stimulation, which have been widely researched on materials with non-centrosymmetric wurtzite structure. Topological insulator (TI) materials with symmetric crystal structure have been theoretically predicted that its photoelectronic properties would also be greatly modulated through strain modulation effect. Here, for the first time, we experimentally demonstrate the strain modulation effect of TI Bi2Se3 nanowires (NWs), opening an innovative way to enhance the optoelectronic performance of TI materials. Single-crystal TI Bi2Se3 NWs were synthesized via a micro-environmental control chemical vapor deposition method. Based on these NWs, a high-performance photodetector (PD) with high responsivity, and broadband detection range from ultraviolet to near-infrared were fabricated. By introducing an external 0.54% compressive strain, the photocurrent and responsivity were enhanced by 97% and 503%, respectively, upon excitation by 442 nm light with an intensity of 17.6 mW/cm2. A theoretical model of the schematic energy band diagram was proposed to illustrate the enhancement mechanism. The results of theoretical calculation indicate that the conduction band of the TI can be modulated by strain, which can then influence the metal-semiconductor (M-S) junction potential for charges transport. This study reports a high-quality TI Bi2Se3 NWs based strain-modulated PDs, broadening the family of strain modulation materials system, and offering a promising material for high-performance broadband detectors.