AVS 53rd International Symposium
    Magnetic Interfaces and Nanostructures Thursday Sessions
       Session MI+EM-ThM

Paper MI+EM-ThM4
Remanent Electrical Spin Injection from Fe into GaAs Edge-Emitting Spin-LEDs

Thursday, November 16, 2006, 9:00 am, Room 2006

Session: Spin Injection
Presenter: G. Kioseoglou, Naval Research Laboratory
Authors: G. Kioseoglou, Naval Research Laboratory
O.M.J. van 't Erve, Philips Research Laboratories
A.T. Hanbicki, Naval Research Laboratory
C.H. Li, Naval Research Laboratory
B.T. Jonker, Naval Research Laboratory
Correspondent: Click to Email
Electron spin polarizations (P@sub spin@) of 40-70% have been obtained in GaAs due to electrical injection from Fe or FeCo contacts using surface-emitting spin-LEDs. In such LEDs, a narrow (100 Å) QW is typically used, and the heavy hole (HH) angular momentum is constrained to lie along the surface normal due to quantum confinement, requiring a similar orientation for the spin of the injected electrons. Since Fe has its magnetization easy axis in the substrate plane, a large magnetic field (>2.2 tesla) along the surface normal is required to saturate the magnetization out-of-plane. To take advantage of the small coercive fields and large remanent in plane magnetizations of Fe, the edge emitting geometry should be developed to facilitate transduction of the spin state variable between the electron spin and optical polarization. Here we demonstrate electrical spin injection from Fe into edge-emitting LEDs with relatively wide QWs (500 and 1000 Å) and compare surface and edge emission spin injection efficiencies. The edge-emitted optical polarization for the 100Å QW spin LED is zero, as expected due to hole spin orientation. For the wider QWs, the confinement energy diminishes and the magnetic field rather than the confinement defines the quantization axis. In this case the HH angular momentum can in principle lie in-plane, co-linear with the electron spin and light propagation direction, enabling a determination of P@sub spin@ via the same selection rules. We find similar spin injection efficiencies for electron spins (contact magnetization) oriented in-plane and normal to the surface. The magnitude of the edge emitted optical polarization is limited at low magnetic fields by the orientation of the HH angular momentum, which is constrained to lie partially out-of-plane due to the reduced symmetry accompanying weak localization at the QW interfaces. This work was supported by ONR.