6 research outputs found
Hole spin injection from a GaMnAs layer into GaAs-AlAs-InGaAs resonant tunneling diodes
We have investigated the polarization-resolved electroluminescence (EL) of a p–i–n GaAs/AlAs/InGaAs resonant tunneling diode (RTD) containing a GaMnAs (x = 5%) spin injector under high magnetic fields. We demonstrate that under hole resonant tunneling condition, the GaMnAs contact acts as an efficient spin-polarized source for holes tunneling through the device. Polarization degrees up to 80% were observed in the device around the hole resonance at 2 K under 15 T. Our results could be valuable for improving the hole-spin injection in GaMnAs-based spintronic devices
Spin polarization of carriers in InGaAs self-assembled quantum rings inserted in GaAs-AlGaAs resonant tunneling devices
In this work, we have investigated transport and polarization resolved photoluminescence (PL) of n-type GaAs-AlGaAs resonant tunneling diodes (RTDs) containing a layer of InGaAs self-assembled quantum rings (QRs) in the quantum well (QW). All measurements were performed under applied voltage, magnetic fields up to 15 T and using linearly polarized laser excitation. It was observed that the QRs’ PL intensity and the circular polarization degree (CPD) oscillate periodically with applied voltage under high magnetic fields at 2 K. Our results demonstrate an effective voltage control of the optical and spin properties of InGaAs QRs inserted into RTDs
Spin injection in n-type resonant tunneling diodes
We have studied the polarized resolved photoluminescence of n-type GaAs/AlAs/GaAlAs resonant tunneling diodes
under magnetic field parallel to the tunnel current. Under resonant tunneling conditions, we have observed two
emission lines attributed to neutral (X) and negatively charged excitons (X−
). We have observed a
voltage-controlled circular polarization degree from the quantum well emission for both lines, with values up to
−88% at 15 T at low voltages which are ascribed to an efficient spin injection from the 2D gases formed at the
accumulation layers
Hole spin injection from a GaMnAs layer into GaAs-AlAs-InGaAs resonant tunneling diodes
We have investigated the polarization-resolved electroluminescence (EL) of a p–i–n GaAs/AlAs/InGaAs resonant tunneling diode (RTD) containing a GaMnAs (x = 5%) spin injector under high magnetic fields. We demonstrate that under hole resonant tunneling condition, the GaMnAs contact acts as an efficient spin-polarized source for holes tunneling through the device. Polarization degrees up to 80% were observed in the device around the hole resonance at 2 K under 15 T. Our results could be valuable for improving the hole-spin injection in GaMnAs-based spintronic devices
Voltage Controlled Electron Spin Dynamics In Resonant Tunnelling Devices
We investigate the electron spin dynamics in a p-type GaAs/AlAs resonant tunnelling device by measuring the time- and polarized-resolved photoluminescence (PL) from the GaAs quantum well under a high magnetic field (15 T). The voltage dependence of the PL transients have revealed various tunnelling processes with different time constants that give rise to distinct spin-polarized carriers injected into the double-barrier structure. © 2014 IOP Publishing Ltd.4716Zutic, I., Fabian, J., Sarma, S.D., Spintronics: Fundamentals and applications (2004) Reviews of Modern Physics, 76 (2), pp. 323-410. , DOI 10.1103/RevModPhys.76.323Fabian, J., Matos-Abiague, A., Ertler, C., Stano, P., Zutic, I., (2010) Acta Phys. Slov., 57, pp. 565-907. , 10.2478/v10155-010-0086-8 0323-0465Wu, M.W., Jiang, J.H., Weng, M.Q., (2010) Phys. 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Diversidade e capacidade simbiótica de rizóbios isolados de nódulos de Mucuna-Cinza e Mucuna-Anã
As espécies de mucuna são muito utilizadas como adubos verdes, e poucas informações estão disponíveis a respeito dos rizóbios nativos capazes de nodulá-las. O objetivo deste trabalho foi avaliar a diversidade e a capacidade simbiótica de isolados bacterianos de nódulos de mucuna-cinza (Mucuna pruriens (L.) DC.) e mucuna-anã (Mucuna deeringiana (Bort.) Merr.). As bactérias foram isoladas de nódulos de mucunas cinza e anã cultivadas em vasos com solos de um sistema de produção agroecológica. Foram isoladas 160 bactérias, sendo 80 de mucuna-anã e 80 de mucuna-cinza, que foram autenticadas e selecionadas para avaliação da capacidade simbiótica. A diversidade dos isolados foi avaliada por meio das características culturais em meio de cultura YMA e da técnica de análise de restrição do produto de PCR do gene 16S rDNA. A inoculação de cinco isolados em mucuna-cinza e dois em mucuna-anã apresentou elevada biomassa da parte aérea. A maioria dos isolados apresentou crescimento rápido e acidificou o meio de cultura. A análise de restrição demonstrou que as bactérias isoladas apresentam baixa similaridade com estirpes de referência, sugerindo a existência de isolados pertencentes a novos grupos, capazes de nodular as mucunas anã e cinza