Thickness-Controlled Three-Dimensional Dirac Semimetal for Scalable High-Performance Terahertz Optoelectronics

The advent of topological semimetals with peculiar band structure and exotic transport provides an unprecedented material platform that allows exploring novel optoelectronics for circumventing technological bottlenecks. Cd₃As₂, a three-dimensional Dirac semimetal, represents a hallmark system for studying nontrivial quantum phenomena led by Dirac/Weyl physics. However, controllable growth and device implementation are still in their infancy due to lack of efficient ways to make use of light-induced effects in semimetals. In this study, highly sensitive, low-energy photodetection up to terahertz (THz) band wavelength along with fast response at room temperature has been implemented in an antenna-assisted Cd₃As₂ planar structure, which is derived from molecular-beam epitaxial growth. It is demonstrated that the THz photodetector based on semimetal Cd₃As₂ films possesses a responsivity of 0.04 A/W and a NEP value of 430 pW/Hz^1/2. Nonequilibrium manipulation of Dirac fermions with thickness-controlled gap phases and an electromagnetic-coupling effect has been well exploited. Our results portray opportunities for developing high-performance, scalable low-energy photodetectors enabled by a Dirac semimetal, which is promising for broadband photoresponses in the highly pursued THz band.