We propose a write scheme for perpendicular spin-transfer torque magnetoresistive random-access memory that significantly reduces the required tunnel current density and write energy. A sub-nanosecond in-plane polarized spin current pulse is generated using the spin-Hall effect, disturbing the stable magnetic state. Subsequent switching using out-of-plane polarized spin current becomes highly efficient. Through evaluation of the Landau-Lifshitz-Gilbert equation, we quantitatively assess the viability of this write scheme for a wide range of system parameters. A typical example shows an eight-fold reduction in tunnel current density, corresponding to a fifty-fold reduction in write energy, while maintaining a 1 ns write time.

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We discuss our approach to realizing all-electrical spin injection and detection in GaAs via ferromagnetic metals and oxide tunnel barriers. A critical requirement is suppression of the formed Schottky barrier, which causes conductivity mismatching and prevents detection in reverse bias. However, initial I-V measurements of engineered GaAs/AlOx/CoFe tunnel contacts still show too high resistance area products in comparison to the semiconductor conductance, due to a large Schottky barrier contribution. To this end, optimized doping levels of the tunnel contacts and semiconductor spin transport region are calculated. Secondly, control over the magnetic properties of injector and detector electrode is established by designing both electrodes to have different switching fields, due to different widths.

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