The α-In2Se3 THz Photodetector

Terahertz (THz) photodetectors are widely used for applications related to security measurements and medicine due to their noninvasive properties; they are also used in the sixth-generation (6G) communication standard. High-performance THz photodetectors are in high demand; 2-D materials with intriguing ultrafast charge transport characteristics are promising candidates for preparing high-performance THz photodetectors. However, only graphene and black phosphorus (BP), which have a high carrier mobility, have been extensively used for fabricating THz photodetectors. THz photodetectors based on other 2-D materials are extremely rare. This work focuses on the 2-D material
$\alpha $
-In
₂
Se
₃
, which has a high carrier mobility, comparable to that of BP. An
$\alpha $
-In
₂
Se
₃
transistor based on the plasma-wave-rectification effect was fabricated as a THz photodetector. The photocurrent of the
$\alpha $
-In
₂
Se
₃
transistor under 0.12-THz illumination is smaller than that measured in dark conditions. Our THz photoresponse result is unusual compared with that of conventional THz devices. Two main factors contribute to this result. When the
$\alpha $
-In
₂
Se
₃
transistor is under 0.12-THz illumination, first, a higher order recombination occurs, and the net carrier concentration then decreases; second, the carrier movement changes from being temperature-activated to being band-like transport, and the carrier mobility then decreases. Therefore, the photocurrent of the
$\alpha $
-In
₂
Se
₃
transistor is smaller than the dark current. Furthermore, the
$\alpha $
-In
₂
Se
₃
transistor has potential uses in memory applications due to the ferroelectricity of
$\alpha $
-In
₂
Se
₃
. Thus, the
$\alpha $
-In
₂
Se
₃
transistor can be developed for use as an artificial photoinhibitory synaptic device in all-optical neural network simulations and low-energy-consumption THz photodetectors.