Room-Temperature Spin Injection And Optical Polarization In Nitride-Based Blue And Ultra-Violet Spin Light-Emitting Diodes

RT spin injection and optical polarization in nitride-based spin-LEDs are investigated. By employing CoFeB/MgO as the spin injector, the spin relaxation time and diffusion length in n-type GaN film are revealed to be 54.9 ps and 214.4 nm, respectively, through the three-terminal Hanle measurement. As the spin injector structure is applied to blue spin-LED, a maximal circular polarization of 3.3% is detected in electroluminescence, with the surface-emitting geometry and under a vertical magnetic field. UV spin-LED with n-Al0.05Ga0.95N transport layer is also fabricated, whose optical polarization is relatively smaller due to the larger spin-orbit coupling in Al atoms.