Husain, M. K., Li, X and De Groot, C. H.
A study on Ge based spin-LED for spintronic applications.
At Condensed Matter and Materials Physics, University of Leicester , UK,
12 - 13 Apr 2007.
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Spintronic applications require solid-state devices in which both spin injection and detection take place electrically. The lack of progress so far made towards this is due to the fact that the requirements for an electrical injection and extraction device are quite different from those for an optical detection device . The strong recombination in the direct-bandgap of III-V semiconductors hampers the effort to create an all electrical device. Therefore it would be interesting to investigate group IV systems to create an electrical spin injection and detection device. In this work, concentration is given to Spin injection into Ge in a Spin-LED consisting of FM/Ge/GaAs/Quantum-Well. The effect of the conduction band offset between Ge and GaAs on the electron transport properties across the interface is investigated for various Ge doping densities. Simulation of a Ge/GaAs heterostructure was performed using ATLAS device simulation software. The calculated conduction band profiles for various doping densities of Ge and the corresponding I-V characteristics are shown in Fig 1a and 1b respectively. At forward bias, with increasing n-type doping densities more electrons go over the barrier increasing the thermionic emission. At reverse bias the current increases with increasing doping in Ge. This can be attributed to the effective lowering of the barrier height predicted by the Thermionic-emission model. Moreover as the barrier thickness is reduced due to reverse bias, electrons with lower energy than the barrier contributes to tunnelling currents. It can be inferred that highly doped Ge could be suitable for the proposed spintronic device.
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