This paper studies the electronic transport property through a square potential barrier in armchair-edge graphene nanoribbon (AGNR). Using the Dirac equation with the continuity condition for wave functions at the interfaces between regions with and without a barrier, we calculate the mode-dependent transmission probability for both semiconducting and metallic AGNRs, respectively. It is shown that, by some numerical examples, the transmission probability is generally an oscillating function of the height and range of the barrier for both types of AGNRs. The main difference between the two types of systems is that the magnitude of oscillation for the semiconducting AGNR is larger than that for the metallic one. This fact implies that the electronic transport property for AGNRs depends sensitively on their widths and edge details due to the Dirac nature of fermions in the system.
The spin-dependent conductance and magnetoresistance ratio (MRR) for a semiconductor heterostructures consisting of two magnetic barriers with different height and space have been investigated by the transfer-matrix method. It is shown that the splitting of the conductance for parallel and antiparallel magnetization configurations results in tremendous spin-dependent MRR, and the maximal MRRs reach 5300% and 3800% for the magnetic barrier spaces W = 81.3 and 243.9 nm, respectively. The obtained spin-filtering transport property of nanostructures with magnetic barriers may be useful to magnetic-barrier-based spintronics.
An InGaAsP-InP transistor laser (TL) working at 1.5 μm and its epitaxy structure with MQW active layer buried between unsymmetrical upper and lower waveguides in base region has been designed and modeled. The simulation result shows that the proposed TL has good optical and lateral electrical current confinement. The result of epitaxial experiment by metalorganic chemical vapor deposition (MOCVD) shows that the diffusion of doped Zn2+ from heavily doped base contactor layer to active waveguide can induce serious degradation of quantum wells. By modeling the Zn2+ diffusion from heavily doped base contactor layer, a gradient doping profile with an average doping density of 1 ( 1018 cm-3 in the base contact layer has been used in the epitaxy process to constrain the Zn2+ diffusion to quantum wells. The test result of the epitaxy material has demonstrated high PL intensity at 1.51 μm and clear satellite diffraction peaks in the XRD spectrum.
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