Direct Wide Bandgap 2D GeSe₂ Monolayer toward Anisotropic UV Photodetection

Abstract

graphene, however, is problematic for many optoelectronic applications. Semiconducting layered metal dichalcogenides (LMDs) have generated an immense amount of interest, owing to their specific bandgaps in the ≈1-2.4 eV range. [2] Most LMDs undergo a transition from an indirect bandgap material in the multilayer form to a direct bandgap material in the monolayer form and exhibit strong lightmatter interaction at the 2D limit. [3,4] All of these features make 2D LMDs promising materials for several applications, such as transistors [5] and optoelectronic [6] and valleytronic [7] devices. Nonetheless, the finite bandgap of such reported LMDs largely restricts their applications in IR and ultraviolet (UV) photodetection. [8] UV photodetection, particularly in the solar blind range (200 to 280 nm), has great potential in the missile detection, flame alarms, and so forth. However, the lack of wide bandgap LMD materials makes realizing 2D UV photodetectors a challenge.As a new important member of the LMD family, germanium diselenide (GeSe 2 ), with a direct wide bandgap, has many potential applications in UV detection and IR waveguides. [9] Moreover, GeSe 2 exhibits a monoclinic crystal structure, [10] within two crystallographically different types of GeSe 4/2 tetrahedra centered on the Ge1 and Ge2 atoms, as shown in As an important 2D layered metal dichalcogenide, germanium diselenide (GeSe 2 ) with a direct wide bandgap is attracting increasing attention for its potential applications in ultraviolet (UV) detection. However, only few-layer GeSe 2 has been reported to date. Here, a joint theoretical-experimental study on the optical and electronic properties of monolayer GeSe 2 is presented, and monolayer GeSe 2 is shown to have a direct wide bandgap of 2.96 eV. Consequently, monolayer GeSe 2 does not respond to a major fraction of the visible spectrum. Notably, the photofield effect transistors based on the GeSe 2 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 GeSe 2 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 GeSe 2 is a promising candidate for highly selective polarization-sensitive UV detection.

Anisotropic 2D SiAs for High‐Performance UV–Visible Photodetectors

“…[35] A reduced anisotropic response at higher photon energy was also observed for GeAs, GeSe, GeSe 2 , TaIrTe 2 , and Te. [14,32,[43][44][45] Our anisotropic ratio at 514.5 nm is higher than those of other IV-V group 2D materials at similar wavelengths: 1.52 for GeP at 532 nm, 3.4 for SiP at 671 nm, 1.49 for GeAs at 520 nm, and 2 for GeAs 2 at 532 nm, respectively. [28,[30][31][32] The anisotropic ratio at 325 nm is also higher than those of GeSe 2 at 266 nm (1.14) and GeS 2 at 325 nm (1.8).…”

Recent Progress of Heterojunction Ultraviolet Photodetectors: Materials, Integrations, and Applications

“…Limited by the availability of wide‐bandgap 2D semiconductors, the progress of UV photodetectors based on 2D materials is restricted 69,70. However, the newly investigated 2D materials of GeSe 2 ,71 Sr 2 Nb 3 O 10 ,11 and GeS 2 72 have shown bandgap of about 3 eV, and they have been fabricated into UV photodetectors showing competitive photoresponse with state‐of‐the‐art UV detectors. As a typical 2D layered semiconductor, the Pb and I atoms of PbI 2 are covalently bonded within each plane and the planes are stacked together by weak vdWs force (Figure 1c).…”

Symmetry‐Reduction Enhanced Polarization‐Sensitive Photodetection in Core–Shell SbI3/Sb2O3 van der Waals Heterostructure

“…Symmetry‐reduction as a method of disordering atoms to change the density of states in a certain direction by heterostructure enhances the dichroic ratio. Therefore, symmetry‐reduction as a valid method of enhancing structural anisotropy can numerously enrich the family of in‐plane anisotropy semiconductors and has extensively utilized in polarization‐sensitive photodetection …”