Direct Wide Bandgap 2D GeSe2 Monolayer toward Anisotropic UV Photodetection

As an important 2D layered metal dichalcogenide, germanium diselenide (GeSe2) with a direct wide bandgap is attracting increasing attention for its potential applications in ultraviolet (UV) detection. However, only few-layer GeSe2 has been reported to date. Here, a joint theoretical-experimental study on the optical and electronic properties of monolayer GeSe2 is presented, and monolayer GeSe2 is shown to have a direct wide bandgap of 2.96 eV. Consequently, monolayer GeSe2 does not respond to a major fraction of the visible spectrum. Notably, the photofield effect transistors based on the GeSe2 monolayer show p-type behavior, high responsivity, superior detectivity, and a fast response time, competitive with state-of-the-art UV detectors. In addition to the excellent photoresponse properties, 2D GeSe2 crystals also exhibit perpendicular optical reversal of the linear dichroism and polarized photodetection under wavelength modulation. Theoretical calculations of the band structure are used to shed light on these experimental results. The findings suggest that 2D GeSe2 is a promising candidate for highly selective polarization-sensitive UV detection.