A floating gate negative capacitance MoS₂ phototransistor with high photosensitivity

Area of Science:

• Materials Science
• Nanotechnology
• Optoelectronics

Background:

• Monolayer MoS₂ shows promise for photodetectors and LEDs.
• Improving light sensitivity requires low dark current for detecting weak signals.
• Existing methods for enhancing photodetector detectivity often lack CMOS compatibility or sufficient dark current suppression.

Purpose of the Study:

• To develop a highly sensitive monolayer MoS₂ phototransistor with low dark current.
• To explore the potential of steep slope transistors in photodetector applications.
• To investigate the device's performance as optical memory and in artificial neural networks.

Main Methods:

• Fabrication of a monolayer MoS₂ floating gate negative capacitance phototransistor.
• Integration of a hafnium-zirconium oxide ferroelectric capacitor.
• Characterization of device performance under weak light illumination.

Main Results:

• Achieved a minimum subthreshold swing (SS_min) of 30 mV dec^-1.
• Demonstrated very low dark currents in the range of 10^-13–10^-14 A.
• Obtained a high detectivity of 7.2 × 10¹⁵ cm Hz^1/2 W^-1 due to enhanced photogating.
• Explored potential for optical memory and synaptic applications with long-term potentiation.

Conclusions:

• The developed phototransistor exhibits high photosensitivity to weak light signals.
• The device structure is suitable for future low-powered optoelectronic applications.
• The integration of ferroelectric materials offers a promising route for advanced photodetector design.