For the full implementation of spintronic circuits, it is necessary to transmit spin information from one device to another. Electrons in semiconductors often suffer from high spin relaxation rates, making electrical transport of spin information highly inefficient. Here, we propose optical transport of spin information as an alternative. We demonstrate that the spin information associated with electrons injected from Co2FeSi and Fe layers into the quantum wells of spin light emitting diodes (spin-LEDs) can be transported optically in the form of circularly polarized light and deciphered electrically via the magnetic field dependence of the photocurrent in a distant detector spin-LED.

We report an energy gap for hole photoexcitation in ferromagnetic Ga 1-x Mn x P that is tunable by Mn concentration (x ≤ 0.06) and by compensation with Te donors. For x~0.06, electrical transport is dominated by excitation across this gap above the Curie temperature (T C ) of 65 K and by thermally-activated hopping below T C . Magnetization measurements reveal a moment of 3.5 µ B per substitutional Mn while the large anomalous Hall signal unambiguously demonstrates that the ferromagnetism is carriermediated. In aggregate these data indicate that ferromagnetic exchange is mediated by holes localized in a Mn-derived band that is detached from the valence band.

We have synthesized GaN x As 1-y P y alloys (x ~ 0.3-1% and y=0-0.4) using nitrogen N ion implantation into GaAsP epilayers followed by pulsed laser melting and rapid thermal annealing techniques. As predicted by the band anticrossing model, the incorporation of N splits the conduction band (E M ) of the GaAs 1-y P y substrate, and strong optical transitions from the valence band to the lower (E -) and upper (E + ) conduction subbands are observed . The relative strengths of the E -and E + transition change as the localized N level E N emerges from the conduction band forming narrow intermediate band for y > 0.3.The results show that GaN x As 1-x-y P y alloys with y>0.3 is a three band semiconductor alloy with potential applications for high-efficiency intermediate band solar cells.PACS numbers: 71.20.Nr; 78.66.Fd; 61.72.Vv; 89.30 The potential technological importance of the multiband semiconductors raises the question if they can also be realized in group III-N x -V 1-x HMAs as well. In most III-V compounds the localized N level lies above the conduction band edge. An exception is the GaAs 1-y P y alloy system in which N-level falls below the conduction band edge for y>0.3. Consequently the anticrossing interaction of the N states with the extended conduction band states in these GaAsP alloys is expected to result in the formation of a narrow band of intermediate states. This is supported by the observation that the fundamental bandgap in GaN x P 1-x is transformed from indirect to direct for x > 0.005. [22][23][24]. However, the novel band structure of GaN x As 1-x-y P y alloys has not been explored [25,26] yet. In this paper we report the synthesis of quaternary GaN x As 1-x-y P y 4 alloys using N + implantation in epitaxially grown GaAsP films followed by pulsed laser melting techniques. We demonstrate that GaN x As 1-x-y P y with y>0.3 is a multiband system that can be exploited for the fabrication of IBSCs. GaN x As 1-x-y P y layers were formed by N + implantation into ~0.5 µm thick GaAs 1-y P y (y=0-0.35) epitaxial films grown by metalorganic chemical vapor deposition (MOCVD) on semi-insulating GaAs substrate. Sequential N + implants with energies of 80 and 33keV with doses of 7x10 15 and 2.4x10 15 cm -2 , respectively, were used to create ~0.2 µm thick layers with a uniform N atomic concentration of ~4.4x10 20 cm -3 (2 mole percent). The implanted structures were subjected to pulsed-laser melting (PLM) in air using a KrF excimer laser (λ=224nm) with pulse duration ~30 ns and photon fluence at the sample between 0.2 and 0.4J/cm 2 . Both the ion implantation and PLM processes are inherently non-equilibrium. Using a pulsed excimer laser, the heavily-damaged layer caused by ion implantation can be melted and recrystallized on time scales on the order of 10 -7 s. Such rapid solidification prevents secondary phase formation even when the equilibrium solubility limit has been exceeded by orders of magnitude [27]. This combined ion beam and laser processing approach has been demonstrated as an effective approac...