Pure circular polarization electroluminescence at room temperature with spin-polarized light-emitting diodes

TL;DR

This study demonstrates room-temperature electroluminescence with nearly pure circular polarization from GaAs-based spin-LEDs without external magnetic fields, highlighting advances in spin-polarized light emission.

Contribution

It introduces a novel GaAs-based spin-LED design achieving high circular polarization at room temperature without external magnetic fields.

Findings

CP purity increases with current density, reaching near 100% at 100 A/cm2

Device structure with stripe-laser-like features and AlOx tunnel barrier enhances performance

Spin-dependent re-absorption and birefringence influence polarization characteristics

Abstract

We report the room-temperature electroluminescence (EL) with nearly pure circular polarization (CP) from GaAs-based spin-polarized light-emitting diodes (spin-LEDs). External magnetic fields are not used during device operation. There are two small schemes in the tested spin-LEDs: firstly, the stripe-laser-like structure that helps intensifying the EL light at the cleaved side walls below the spin injector Fe slab, and secondly, the crystalline AlOx spin tunnel barrier that ensures electrically stable device operation. The purity of CP is depressively low in the low current density (J) region, whereas it increases steeply and reaches close to the pure CP when J = 100 A/cm2. There, either right- or left-handed CP component is significantly suppressed depending on the direction of magnetization of the spin injector. Spin-dependent re-absorption, spin-induced birefringence and optical spin-axis conversion are suggested to account for the observed experimental results.