Negative Photoconductivity of Fe₃GeTe₂ Crystal with Native Heterostructure for Ultraviolet to Terahertz Ultra-Broadband Photodetection.

Abstract

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.