Semiconductor-baaed magneto-photonic crystals and their applications

点击翻译按钮获取中文摘要

We have successfully grown a new quaternary alloy magnetic semiconductor (InGaMn)As, and have found that it is ferromagnetic with T_c〜130K. In (InGaMn)As, the lattice constant and the bandgap can be changed, and it can be grown on lattice-matched InP substrates, thus having good compatibility with optical communication devices. More recently, we have realized high T_c of 172-250K in Mn-delta-doped GaAs/p-AlGaAs heterostructures, which are the highest values ever reported in III-V based materials. Recently, we find out the giant planar Hall effect in Mn-delta-doped GaAs/p-AlGaAs heterostructures and clarified the magnetic anisotropy. Such new magnetic quantum heterostructures are very attractive in view of fundamental research as well as potential applications to "spintronics".Recently, we observed negative TMR and oscillations of the TMR ratio (with varying the AlAs thickness) in GaMnAs/AlAs/InGaAs/AlAs/GaMnAs double-barrier ferromagnetic tunnel junctions, for the first time in magneti … More c semiconductor systems. This is caused by the appearance of resonant tunneling and TMR effects at the same time. Realization of such large spin-dependent tunneling in semiconductor heterostructures, that is spin injection from one semiconductor layer to another semiconductor layer via tunneling, is an very significant step towards future spintronics, in which one tries to use the spin degree of freedom in semiconductor devices.We have fabricated ferromagnet(MnAs)/III-V semiconductor(GaAs) granular structures, hereafter GaAs : MnAs, by annealing (GaMn)As at 500-800℃. During the annealing process, MnAs ferromagnetic clusters with diameters of a few nm were formed in a matrix of GaAs (or GaMnAs), exhibiting a superparamagnetic behavior. We have established the fabrication process and have measured magneto-optic properties. Furthermore, we have fabricated GaAs:MnAs sandwiched by GaAs/AlAs distributed Bragg Reflectors (DBRs), and have showed significant enhancement of magneto-optical effect by using multiple interference and localization of light in the GaAs:MnAs magnetic layer. This structure offers new opportunity for the application to spin-controlled photonic devices based on III-V compound semiconductors. Recently, we have found extremely large positive magnetoresistance of 600 % at room temperature in the GaAs:MnAs granular structures, and further investigations are underway. Less