Negative Photoconductivity of Fe₃GeTe₂ Crystal with Native Heterostructure for Ultraviolet to Terahertz...

Gaining insight into the photoelectric behavior of ferromagnetic materials is significant for comprehensively grasping their intrinsic properties and broadening future application fields. Here, through a specially designed Fe₃GeTe₂/O-Fe₃GeTe₂ heterostructure, first, the broad-spectrum negative photoconductivity phenomenon of ferromagnetic nodal line semimetal Fe₃GeTe₂ is reported that covers UV-vis-infrared-terahertz bands (355 nm to 3000 µm), promising to compensate for the inadequacies of traditional optoelectronic devices. The significant suppression of photoexcitation conductivity is revealed to arise from the semimetal/oxidation (sMO) interface-assisted dual-response mechanism, in which the electron excitation origins from the semiconductor photoconductivity effect in high-energy photon region, and semimetal topological band-transition in low-energy photon region. High responsivities ranging from 10³ to 10⁰ mA W^-1 are acquired within ultraviolet-terahertz bands under ±0.1 V bias voltage at room temperature. Notably, the responsivity of 2.572 A W^-1 at 3000 µm (0.1 THz) and the low noise equivalent power of 26 pW Hz^-1/2 surpass most state-of-the-art mainstream terahertz detectors. This research provides a new perspective for revealing the photoelectric conversion properties of Fe₃GeTe₂ crystal and paves the way for the development of spin-optoelectronic devices.