Spin-polarized light-emitting diodes with Mn-doped InAs quantum dot nanomagnets as a spin aligner.
ABSTRACT We have fabricated and characterized surface-emitting, spin-polarized light-emitting diodes with a Mn-doped InAs dilute magnetic quantum dot spin-injector and contact region grown by low-temperature molecular beam epitaxy, and an In(0.4)Ga(0.6)As quantum dot active region. Energy-dispersive X-ray and electron energy loss spectroscopies performed on individual dots indicate that the Mn atoms incorporate within the dots themselves. Circularly polarized light is observed up to 160 K with a maximum degree of circular polarization of 5.8% measured at 28 K, indicating high-temperature spin injection and device operation.
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ABSTRACT: The electronic structure, spin splitting energies, and g factors of paramagnetic In 1-x Mn x As nanowires under magnetic and electric fields are investigated theoretically including the sp-d exchange interaction between the carriers and the magnetic ion. We find that the effective g factor changes dramatically with the magnetic field. The spin splitting due to the sp-d exchange interaction counteracts the Zeeman spin splitting. The effective g factor can be tuned to zero by the external magnetic field. There is also spin splitting under an electric field due to the Rashba spin-orbit coupling which is a relativistic effect. The spin-degenerated bands split at nonzero k z (k z is the wave vector in the wire direction), and the spin-splitting bands cross at k z =0, whose k z -positive part and negative part are symmetrical. A proper magnetic field makes the k z -positive part and negative part of the bands asymmetrical, and the bands cross at nonzero k z . In the absence of magnetic field, the electron Rashba coefficient increases almost linearly with the electric field, while the hole Rashba coefficient increases at first and then decreases as the electric field increases. The hole Rashba coefficient can be tuned to zero by the electric field. Copyright EDP Sciences/Società Italiana di Fisica/Springer-Verlag 2007Physics of Condensed Matter 01/2007; 58(3):263-268. · 1.28 Impact Factor
Article: Piezomagnetic quantum dots.[show abstract] [hide abstract]
ABSTRACT: We study the influence of deformations on magnetic ordering in quantum dots doped with magnetic impurities. The reduction of symmetry and the associated deformation from circular to elliptical quantum confinement lead to the formation of piezomagnetic quantum dots. The strength of elliptical deformation can be controlled by the gate voltage to change the magnitude of magnetization, at a fixed number of carriers and in the absence of an applied magnetic field. We reveal a reentrant magnetic ordering with the increase of elliptical deformation and suggest that the piezomagnetic quantum dots can be used as nanoscale magnetic switches.Physical Review Letters 12/2008; 101(20):207202. · 7.94 Impact Factor