Full-zone optical spin injection in AlxGa1-xAs alloys

Abstract Full-zone optical spin-injection in Al x Ga 1-x As alloys is investigated by analysing the degree of circular polarization (DCP) of luminescence in a quantum well architecture. Aluminium content in AlGaAs barrier layers is varied to explore both the direct and indirect bandgap regime. For all the samples, experimental data are compared with a 30 band k.p model addressing the band-structure of the alloy and the optical spin injection over the entire Brillouin zone. We observe circularly-polarized luminescence arising from the spin generation either around Γ or L valley. We interpret the specific shape of the DCP within a framework accounting smaller electron spin relaxation in the higher k points of the X valley of AlGaAs barrier layer. Moreover, it is found that the presence of strain plays a vital role in governing the magnitude and shape of the degree of circular polarization spectra for near band edge excitation while exciting spin-polarized carriers in the direct bandgap AlGaAs.. We believe that these findings are important for the realization of AlGaAs based spin-photonic devices aiming possible applications in quantum technology.