Influence of MgO Tunnel Barrier Thickness on the Output Power of Three-Terminal Spin Hall Nano-Oscillators

Abstract

Magnetic tunnel junction nanopillar devices were patterned into three-terminal spin Hall nano-oscillators starting from a 200 mm wafer with an MgO barrier wedge with a nominal thickness variation between 0.72 and 1.36 nm. The resulting devices, with $R \times A$ values in the range between 1 and $110~\Omega \cdot \mu \text {m}^{2}$ , were characterized in the frequency domain in an attempt to optimize the MgO barrier thickness with respect to the nano-oscillators output power. While all the devices exhibit oscillations, the integrated matched output power reaches a maximum of 12.5 nW for an $R \times A$ of $34~\Omega \cdot \mu \text{m}^{2}$ with a nominal MgO thickness of 1.2 nm.