Abstract
The difficulty of spin injection from a ferromagnetic metal into a semiconductor originates from the conductivity mismatch between these materials. The spin-polarized light-emitting diode (spin-LED) is a very powerful means for accurately quantifying spin injection through detecting left and right circular polarized light. In this work, we have investigated the spin-LEDs made of Fe3Si/GaAs heterostructures. Fe3Si, as a Heusler alloy, is expected to be half metal with 100% spin polarization at the Fermi level, thus making Fe3Si an attractive material for spin injection. The film growth was conducted in a UHV, multi-chamber integrated system. After III-V growth, the sample was transferred in-situ to another chamber for depositing 150 Å thick Fe3Si film epitaxially grown on GaAs(100) surface with -0.2% lattice mismatch. Our optical measurements have demonstrated the successful enhancement of the LED brightness by 1000 times through systematic improvements of the fabrication process and design of the LED structure. Furthermore, a tunnel barrier is known to remove the problem of the conductivity mismatch between a ferromagnetic metal and a semiconductor, thus increasing the spin polarization efficiency. In the research, I use doping engineering to form a Schottky barrier at Fe3Si and semiconductor. And Among many materials candidates as tunnel barriers, we plan to employ crystalline MgO oxide films to investigate the spin injection of Fe3Si/MgO/GaAs tunnel junction in the future.