Two-dimensional wide-bandgap GeSe2 vertical ultraviolet photodetectors with high responsivity and ultrafast response speed

Abstract

Germanium selenide (GeSe₂), as a typical member of 2D wide bandgap semiconductors (WBSs), shows great potential in ultraviolet (UV) optoelectronics due to its excellent flexibility, superior environmental stability, competitive UV absorption coefficient, and significant spectral selectivity. However, the GeSe₂-based UV photodetector suffers from high operation voltages and low photocurrent, which prevents its practical imaging applications. In this work, we report an elevated photocurrent generation in a vertical stacking graphene/GeSe₂/graphene heterostructure with low operation voltage and low power consumption. Efficient collection of photoexcited carriers in GeSe₂ through graphene electrodes results in outstanding UV detection properties, including a pronounced responsivity of 37.1 A W⁻¹, a specific detectivity of 8.83 × 10¹¹ Jones, and an ultrahigh on/off ratio (∼10⁵) at 355 nm. In addition, building a Schottky barrier between GeSe₂ and graphene and reducing the channel length can increase the photoresponse speed to ∼300 μs. These accomplishments set the stage for future optoelectronic applications of vertical 2D WBS heterostructure UV photodetectors.