Ultrasensitive and broadband polarization-sensitive topological insulator photodetector induced by element substitution.

Topological insulators are considered as one of the preferred materials for high-performance optoelectronic devices due to their small bulk bandgaps and ultra-high carrier mobility. However, the existence of their unique Dirac like surface states makes the corresponding optoelectronic devices to have high dark current, and the logic circuit cannot be turned off effectively. Opening the surface state gap by element doping is an effective means to achieve high performance of devices. Here, we design and prepare single crystal Bi2Se2.15S0.85 nanowires by a facile iodine-assisted chemical vapor transport method and a fabricated individual Bi2Se2.15S0.85 nanowire based photodetector. The devices exhibit remarkable photoresponse over the broadband wavelength ranging from ultraviolet C (275 nm) to near-infrared (1310 nm) with the low dark current of 10−12 A. They show superior optoelectrical properties with an ultrafast response speed of 170 ns, detectivity of 9.35 × 1011 Jones, a competitive responsivity of 1.31 A/W, and superb stability to keep great photoresponse for at least one year, which are superior to the reported photodetectors. Additionally, benefiting from the anisotropic crystal structure of Bi2Se2.15S0.85, the devices also display good polarization detection performance in a wide spectral range from 266 nm to 1064 nm with a dichroic ratio of 1.81 at 360 nm. [ABSTRACT FROM AUTHOR]