n-Type GaSe Thin Flake for Field Effect Transistor, Photodetector, and Optoelectronic Memory

The family of 2D chalcogenide semiconductors has been growing rapidly. Metal monochalcogenides, for instance, can enable new possibilities in functional electronics and optoelectronics. A Gallium Selenide (GaSe) thin flake is used to fabricate a back gated field effect transistor (FET) with n-type conduction behavior and wide hysteresis at the ambient conditions. The device shows high mobility up to 28 cm² V⁻¹ s⁻¹ with I_on/I_off ratio over 10³. Under the laser exposure, the device shows a decrease in the threshold voltage and a left-shift of the transfer characteristic with a slight increase in the current. The transfer characteristic exhibits a hysteretic behavior with hysteresis width linearly dependent on the applied gate voltage. Moreover, the GaSe-based FET shows a photo response with a photoresponsivity of 475 mAW⁻¹ and detectivity of 4.6 × 10¹² Jones. The photocurrent rise and decay times are 0.1 and 1.3 s, respectively. Furthermore, the GaSe FET device can be used as a performant memory device with well separated states and memory window enhanced by the laser exposure, confirming an optoelectronic memory class.