Gate-voltage-induced switching of the Rashba spin-orbit interaction in a composition-adjusted quantum well

Abstract

The coefficient $\ensuremath{\alpha}$ of the Rashba spin-orbit interaction is calculated in an asymmetric quantum well consisting of ${\mathrm{Ga}}_{0.47}{\mathrm{In}}_{0.53}\mathrm{As}$ (well), ${\mathrm{Al}}_{0.48}{\mathrm{In}}_{0.52}\mathrm{As}$ (left barrier), and ${\mathrm{Al}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{As}}_{y}{\mathrm{Sb}}_{1\ensuremath{-}y}$ (right barrier) as a function of the external electric field perpendicular to the well ${E}_{z}^{\mathrm{ex}}$ which is controlled by the gate voltage. This coefficient $\ensuremath{\alpha}$, which depends on the band offset, can be tuned to be zero by adjusting the Al fraction $x$ in the right barrier layer to the optimum value ${x}_{0}$ in the case where the wave function vanishes at the left heterointerface. Such a composition-adjusted asymmetric quantum well is proposed as a structure in which the magnitude of $\ensuremath{\alpha}$ can be switched by changing the polarity of ${E}_{z}^{\mathrm{ex}}$. The calculation shows that, when $|x\ensuremath{-}{x}_{0}|l0.01$, the on/off $|\ensuremath{\alpha}|$ ratio $g40$ for a large enough $|{E}_{z}^{\mathrm{ex}}|$ ($|{E}_{z}^{\mathrm{ex}}|g{10}^{7}$ V/m for a well width of 20 nm), which results in the on/off spin-relaxation-rate ratio exceeding ${10}^{3}$ in the Dyakonov-Perel mechanism.