Electrostatically enhanced infrared absorption in two-dimensional van der Waals structures

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Two-dimensional (2D) semiconductors offer strong light absorption but possess large bandgaps, limiting broadband photodetection.
• Van der Waals (vdW) heterostructures can narrow bandgaps for infrared excitation, but controlling interlayer transitions is challenging.

Purpose of the Study:

• To establish a correlation between interfacial charge redistribution and enhanced interlayer excitations in 2D vdW structures.
• To explore engineering strategies for optimizing interlayer transitions in 2D vdW heterostructures for photodetection.

Main Methods:

• Utilized first-principles simulations to investigate electronic properties.
• Employed electrostatic engineering approaches, including external electric fields, substitutional doping, and graphene interlayers.
• Analyzed interfacial charge redistribution and bandgap modulation.

Main Results:

• Demonstrated that external electric fields, doping, and graphene interlayers reduce interlayer bandgaps by hundreds of millielectronvolts.
• Showcased significant increases in interfacial charge exchange through these engineering strategies.
• Achieved absorption coefficients exceeding 10^5 cm^-1 across visible to mid-infrared wavelengths.

Conclusions:

• Established a direct link between interfacial charge redistribution and enhanced interlayer excitations in 2D vdW structures.
• Provided versatile engineering strategies for reducing bandgaps and increasing charge exchange.
• Offered essential design principles for developing high-performance broadband photodetectors using 2D vdW materials.