High Detectivity Graphene-Silicon Heterojunction Photodetector.

Area of Science:

• Materials Science
• Optoelectronics
• Semiconductor Devices

Background:

• Graphene/n-type silicon (n-Si) heterojunctions show promise for photodetectors due to rectifying behavior and photoresponsivity.
• Previous devices had limited specific detectivity because of high dark currents.

Purpose of the Study:

• To enhance the specific detectivity of graphene/n-Si heterojunction photodetectors.
• To reduce dark current by introducing an interfacial oxide layer.

Main Methods:

• Fabrication of graphene/n-Si heterojunctions with a thin interfacial oxide layer.
• Characterization of electrical and photoresponse properties, including dark current, responsivity, photo-to-dark current ratio, and current noise spectral density.
• Performance evaluation under ambient and vacuum conditions.

Main Results:

• The interfacial oxide layer reduced dark current by two orders of magnitude at zero bias.
• Achieved a specific detectivity of 5.77 × 10^13 cm Hz^(1/2) W^(-1) at 890 nm in vacuum at room temperature.
• Demonstrated high responsivity (0.73 A W^(-1)) and an exceptional photo-to-dark current ratio (≈10^7).
• Dark current suppression was further observed in vacuum.

Conclusions:

• The interfacial oxide layer effectively suppresses dark current in graphene/n-Si heterojunctions.
• The optimized photodetectors exhibit record-high specific detectivity for planar graphene/Si devices at room temperature.
• Graphene/Si heterojunctions with interfacial oxides are highly promising for developing high-performance, high-detectivity photodetectors.