Topological Insulator Based Dual State Photo‐Switch Originating Through Bulk and Surface Conduction Channels

Abstract

Topological insulators are novel electronic materials, where time reversal symmetry protects the spin‐polarized surface states from backscattering. Although, the bulk offers a trivial semiconducting response to incident light, but the metallic surface states exhibit interesting electrical response towards the incident radiation, such as polarization dependent surface photocurrent and topological phase transitions. Here, we study the temperature dependent near‐infrared photoresponse in bismuth selenide (Bi2Se3) nano‐flakes. A very good photo‐sensitivity to near‐infrared 800 nm wavelength is observed for the temperature range 300–2 K. Voltage responsivity at 2 K (1.481 × 1010 VW−1) is estimated to be four‐order greater than at 300 K (2.095 × 106 VW−1) and is comparatively much higher than the previously reported values of voltage responsivity in other materials. Interestingly, we also find the temperature dependent existence of both positive and negative photoresponse in our device. An anomalous photoresponse reversal is observed at 2 K, where resistance of the nano‐flake increases under light illumination. We propose that this phenomenon is due to the topological surface states, which have dominant transport contribution at very low temperatures. These observations establish the fact that topological insulators can be further engineered to develop a dual state photo‐switch, by manipulating the bulk and surface state conduction contribution.

High performing flexible optoelectronic devices using thin films of topological insulator

“…It indicates that more carriers are excited in the thick films which could be due to the bulk contribution. The earlier literature suggests that in topological insulator material there is a possibility of photocurrent contributions originating from the bulk of the sample as well as from the surface states also 47 , 49 , 50 . Thickness dependent optical properties were studied theoretically and decrease in optical conductivity was observed with decrease in thickness of the film 48 .…”

Ultrahigh Stability 3D TI Bi2Se3/MoO3 Thin Film Heterojunction Infrared Photodetector at Optical Communication Waveband

“…Therefore, the photocurrent generated by the device is larger than that generated by pure materials. In addition, the ultrahigh photocurrent of the device is also related to the TSS of Bi 2 Se 3 , which provides a surface channel for carriers to pass quickly …”

“…In addition, the ultrahigh photocurrent of the device is also related to the TSS of Bi 2 Se 3 , which provides a surface channel for carriers to pass quickly. [39] The R i , EQE, and D* curves are calculated according to the corresponding formulas above-mentioned (Figure 3b-d).…”

Epitaxial Growth of Topological Insulators on Semiconductors (Bi2Se3/Te@Se) toward High‐Performance Photodetectors

“…Topological insulators (TIs), a class of nontrivial quantum matter simultaneously possessing insulating bulk states and the time reversal symmetry protected Dirac‐like surface states, have been extensively applied in superconductors, thermoelectric devices, and novel photoelectronic devices . Among all TIs, bismuth selenide (Bi 2 Se 3 ) has been confirmed as an outstanding TI due to its unique characteristics like small bandgap of about 0.35 eV, high surface mobility (10 4 cm 2 V −1 s −1 ), dual photoconductivity response property, superior electrical conductivity, and excellent photoconductivity . The intrinsic small bandgap nature allows Bi 2 Se 3 to absorb light over a broad wavelength range, while the robust topological structure makes Bi 2 Se 3 maintain stable in ambient or harsh environment .…”