Topological meron lattice enabled GaN spin-LEDs with enhanced circular polarization at room temperature

Conventional spin-polarized light-emitting diode (spin-LEDs) exhibit limited circular polarization (CP) ratios (<10%) at room temperature (RT) and polarization degradation at elevated currents, hindering practical applications. This work demonstrates a GaN-based blue spin-LED that leverages a topological meron-antimeron lattice to achieve highly circularly polarized electroluminescence at RT without external magnetic fields. The spin injector, comprising Pd/Fe/MgO multilayers epitaxially grown under a 9 T magnetic field, features atomically sharp interfaces and enhanced crystallinity, with meron–antimeron pairs exhibiting alternating Bloch-type spin configurations confirmed by real-space Lorentz transmission electron microscopy. The device achieves a CP degree ( P c ) exceeding 20%, surpassing conventional nitride-based spin-LEDs, and exhibits a counterintuitive P c increase (Δ P c ≈ 5.3%–7.8%) at higher injection currents (2 mA). This phenomenon originates from chiral spin textures generating Berry-phase-derived equivalent magnetic fields, which suppress Dyakonov–Perel spin relaxation. A polarization quantum efficiency (η T = EQE × P c ) is introduced to holistically evaluate spin-to-photon conversion efficiency. These results establish meron lattices as a robust platform for spin-optoelectronic integration, offering transformative potential for optical communications, quantum technologies, and energy-efficient displays.