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

The coefficient alpha of the Rashba spin-orbit interaction is calculated in an asymmetric quantum well consisting of Ga0.47In0.53As (well), Al0.48In0.52As (left barrier), and AlxGa1-xAsySb1-y (right barrier) as a function of the external electric field perpendicular to the well E-z(ex) which is controlled by the gate voltage. This coefficient 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 a can be switched by changing the polarity of E-z(ex). The calculation shows that, when vertical bar x - x(0)vertical bar < 0.01, the on/off vertical bar alpha vertical bar ratio > 40 for a large enough vertical bar E-z(ex)vertical bar (vertical bar E-z(ex)vertical bar > 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.