Abstract-Warping effect-induced optical absorbance increment of topological insulator films for THz photodetectors with high signal-to-noise ratio

http://pubs.rsc.org/en/Content/ArticleLanding/2014/NR/C3NR06506E#!divAbstract

J. M. Shao,^a   H. Li^a and   G. W. Yang*^a  

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State Key Laboratory of Optoelectronic Materials and Technologies, Institute of Optoelectronic and Functional Composite Materials, Nanotechnology Research Center, School of Physics & Engineering, Sun Yat-sen University, Guangzhou 510275, P.R. China
E-mail: stsygw@mail.sysu.edu.cn

Nanoscale, 2014, Advance Article

DOI: 10.1039/C3NR06506E
Received 08 Dec 2013, Accepted 13 Jan 2014
First published online 27 Feb 2014

Strong optical absorbance makes topological insulator (TI) surfaces a promising high-performance photodetector in the terahertz (THz) to infrared frequency range. Here, we study the optical absorbance of more realistic TI films with hexagonal warping effect using the Fermi's golden rules. It was found that when the warping term is λ ≠ 0, the absorbance is no longer a universal value as that of graphene or ideal Dirac cone, but increases monotonously with the photon energy. The increment is positively correlated with the parameter λ/v_F³ where v_F is the Fermi velocity. The relative signal-to-noise ratio (SNR) of the TI film working as a photoresistor-type photodetector is significantly enhanced by the warping effect-induced absorbance increment. These investigations provide useful information for developing TI-based photodetectors with high SNR in the range of THz to infrared frequency.