Tunable 2H–TaSe₂ room-temperature terahertz photodetector

Two-dimensional transition metal dichalcogenides (TMDs) provide fertile ground to study the interplay between dimensionality and electronic properties because they exhibit a variety of electronic phases, such as semiconducting, superconducting, charge density waves (CDW) states, and other unconventional physical properties. Compared with other classical TMDs, such as Mott insulator 1T–TaS₂ or superconducting 2H–NbSe₂, bulk 2H–TaSe₂ has been a canonical system and a touchstone for modeling the CDW measurement with a less complex phase diagram. In contrast to ordinary semiconductors that have only single-particle excitations, CDW can have collective excitation and carry current in a collective fashion. However, manipulating this collective condensation of these intriguing systems for device applications has not been explored. Here, the CDW-induced collective driven of non-equilibrium carriers in a field-effect transistor has been demonstrated for the sensitive photodetection at the highly-pursuit terahertz band. We show that the 2H–TaSe₂-based photodetector exhibits a fast photoresponse, as short as $14\mu s$, and a responsivity of over 27 V/W at room temperature. The fast response time, relative high responsivity and ease of fabrication of these devices yields a new prospect of exploring CDW condensate in TMDs with the aim of overcoming the existing limitations for a variety of practical applications at THz spectral range. (topical review)