Momentum-Direct Infrared Interlayer Exciton and Photodetection in Multilayer van der Waals Heterostructures

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Interlayer excitons (IX) are crucial quasiparticles in type-II van der Waals heterostructures (vdWH).
• Existing research primarily focuses on momentum-indirect IX with visible light emission, neglecting momentum-direct IX and infrared absorption vital for device applications.

Purpose of the Study:

• To propose and construct a WSe2/InSe vdWH hosting momentum-direct IX and near-infrared interlayer absorption.
• To characterize the IX properties and demonstrate a functional near-infrared vdWH photodetector.

Main Methods:

• First-principles density functional theory calculations.
• Power- and temperature-dependent photoluminescence spectroscopy.
• Fabrication and characterization of a near-infrared vdWH photodetector.

Main Results:

• Demonstrated a multilayer WSe2/InSe vdWH with momentum-direct IX and near-infrared absorption at room temperature.
• Measured an IX binding energy of 43 ± 5 meV and electrically tuned IX energy by 180 meV.
• Achieved a near-infrared photodetector with photoresponsivity of 33 A W⁻¹, detectivity of 1.8 × 10¹⁰ Jones, and response time of 3.7 μs at 1150 nm.

Conclusions:

• The developed WSe2/InSe vdWH successfully hosts momentum-direct IX and exhibits infrared absorption.
• The study demonstrates the potential for infrared-responsive vdWHs with momentum-direct IX in optoelectronic devices.
• The fabricated photodetector shows promising performance for near-infrared detection and imaging applications.