Valley-Selective Linear-Polarization Photodetectors Based on the Photogating Heterostructure of SnS/Si

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Two-dimensional (2D) group-IV monochalcogenides offer anisotropy for polarization-resolved photonic devices.
• Understanding valley-selective photocurrent dynamics in these materials is crucial for device development.
• Challenges exist in optimizing device performance without sacrificing dichroic properties.

Purpose of the Study:

• To fabricate and characterize polarization-resolved photodetectors using tin sulfide (SnS) flakes.
• To investigate the valley-selective anisotropic photocurrent dynamics in SnS.
• To demonstrate high-performance, silicon-compatible photonic devices.

Main Methods:

• Fabrication of SnS/Si photodetectors using as-grown SnS flakes and a dry-transfer technique.
• Measurement of photocurrent response under 405 nm linearly polarized light.
• Analysis of photoelectric dichroism and its relation to valley polarization.

Main Results:

• The fabricated SnS/Si photodetectors exhibited a photocurrent response preferential along the zigzag direction with a dichroic ratio of 1.28.
• Photoelectric dichroism was attributed to polarized photoexcitation of in-plane valleys in SnS, dominated by the zigzag-polarized valley with the smallest bandgap.
• High responsivity (4.54 A W⁻¹) and detectivity (4.76 × 10¹⁰ Jones) were achieved due to photogating gain, enabling enhanced self-powered operation.

Conclusions:

• Fundamental transport evidence for valley-selective photocurrent in SnS flakes was provided.
• The findings support the use of SnS for polarization-sensitive photonic applications.
• A viable route towards multifunctional, silicon-compatible photonic devices was demonstrated.