Spin-polarized light-emitting diodes based on CrI₃ operating without external spin injection.

Area of Science:

• Spintronics
• Materials Science
• Optoelectronics

Background:

• Spin-polarized light-emitting diodes (SPLEDs) are crucial for on-chip information processing, converting electron spin to circularly polarized light.
• Existing SPLEDs often use GaAs-based emitters, requiring complex epitaxial growth and facing challenges in achieving high circular polarization.
• Efficient spin injection, transport, and recombination are critical for high-performance SPLEDs, necessitating high-quality materials.

Purpose of the Study:

• To develop an alternative approach for SPLEDs using monolayer chromium triiodide (CrI₃) as the light-emitting material.
• To investigate the feasibility of using graphene/hexagonal boron nitride tunneling contacts for carrier injection.
• To demonstrate controllable circular polarization of electroluminescence governed by the magnetic order of CrI₃.

Main Methods:

• Fabrication of a heterostructure device with monolayer CrI₃ sandwiched between graphene/hexagonal boron nitride tunneling contacts.
• Electrical characterization of carrier injection and electroluminescence (EL) properties.
• Investigation of the magnetic field dependence of EL polarization.

Main Results:

• Electroluminescence exhibiting circular polarization was achieved despite injection of unpolarized carriers.
• The polarization helicity was directly controlled by the magnetic order of the monolayer CrI₃ emitter.
• A significant degree of polarization (20%) was observed, reversible with a low magnetic field (~0.17 T).

Conclusions:

• Monolayer CrI₃ serves as an effective emitter for SPLEDs, offering an alternative to traditional GaAs-based devices.
• The heterostructure approach demonstrates inherent integrability, simplifying device fabrication.
• This CrI₃-based platform presents a promising avenue for future on-chip spin-optoelectronic applications.