  We have synthesized high-quality, micrometer-sized, single-crystal GeSe
nanosheets using vapor transport and deposition techniques. Photoresponse is
investigated based on mechanically exfoliated GeSe nanosheet combined with Au
contacts under a global laser irradiation scheme. The nonlinearship,
asymmetric, and unsaturated characteristics of the I-V curves reveal that two
uneven back-to-back Schottky contacts are formed. First-principles calculations
indicate that the occurrence of defects-induced in-gap defective states, which
are responsible for the slow decay of the current in the OFF state and for the
weak light intensity dependence of photocurrent. The Schottky photodetector
exhibits a marked photoresponse to NIR light illumination at a wavelength of
808 nm. The significant photoresponse and good responsitivity suggests its
potential applications as photodetectors.
