In past few years, transition metal dichalcogenides (TMDs), such as molybdenum disulfide (MoS2), molybdenum diselenide (MoSe2), tungsten disulfide (WS2), tungsten diselenide (WSe2), have attracted great research interests due to their superior electronic, optical, and mechanical properties. In particular, excellent absorbance (5-10 %) and high quantum efficiency (~104 %) have allowed TMDs to be exploited as channel materials in high-performance photodetectors with high responsivity and high detectivity. However, most TMD photodetectors operated in the limited detection range from ultraviolet to visible region (10 ~ 780 nm) because TMDs generally have an energy bandgap between 1 and 2 eV. Although it was possible to detect 1064 nm and 980 nm lights by utilizing rhenium diselenide (ReSe2) and multi-layer MoS2 with relatively small bandgap (1 and 1.3 eV, respectively), no further researches to detect lights with longer wavelength by using TMD materials were reported yet.
Here, we demonstrate a highly responsible IR photodetector operating based on the interlayer optical transition phenomenon. This IR photodetector formed on ReS2/ReSe2 heterostructure not only extended the detection range up to IR region (1310 nm) that individual ReS2- and ReSe2- photodetectors cannot cover, but also maintained high responsivity even under IR region (3.64 × 105 A/W at λ = 980 nm and 1.58 × 105 A/W at λ = 1310 nm). The small interlayer bandgap of 0.62 eV formed at the ReS2/ReSe2 heterojunction interface lead to the interlayer optical transition phenomenon, consequently enabling photocarriers to be easily generated with less energy than the band-to-band transition.
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