Waveguide-Integrated MoTe₂ p-i-n Homojunction Photodetector

Area of Science:

• Materials Science
• Nanotechnology
• Photonics

Background:

• Two-dimensional (2D) materials offer unique electronic and optical properties for on-chip photodetectors.
• Existing photoconductive devices often struggle with high dark current or low responsivity.
• Photonic integrated circuits require efficient and sensitive photodetection components.

Purpose of the Study:

• To demonstrate a high-performance on-chip photodetector using a molybdenum ditelluride (MoTe2) p-i-n homojunction.
• To integrate the MoTe2 device onto a silicon photonic crystal (PC) waveguide for enhanced light-matter interaction.
• To achieve ultralow dark current, high responsivity, and fast response speeds in the telecommunication O-band.

Main Methods:

• Fabrication of a MoTe2 p-i-n homojunction directly on a silicon PC waveguide.
• Utilizing a split silicon PC waveguide as back gates for selective doping of MoTe2.
• Characterization of device performance including dark current, responsivity, and response bandwidth.

Main Results:

• Successfully realized reconfigurable MoTe2 homojunctions (p-i-n, n-i-p, n-i-n, p-i-p) with rectification and ideality factors near 1.0.
• Achieved ultralow dark currents (<90 pA) and high photoresponsivity (0.4 A/W) in the telecommunication O-band.
• Demonstrated a high light-on/off current ratio (>10^4), a record normalized photocurrent-to-dark-current ratio (10^6 mW^-1), and a high dynamic response bandwidth (~34.0 GHz).

Conclusions:

• The developed MoTe2 p-i-n homojunction on a silicon PC waveguide offers a promising solution for on-chip photodetection.
• The device design enhances light-2D material interaction and enables versatile 2D material heterojunctions.
• This work paves the way for advanced 2D material-based devices such as photodetectors, laser diodes, and electro-optic modulators on silicon photonic chips.