  We show that the tunable gate voltage in n-doped AlGaAs/GaAs QW (quantum
well) is a key in designing an efficient and ultrafast MRAM (magnetoresistive
random access memory). The Rashba spin-orbit coupling in such QWs can be tuned
appropriately by the gate voltage to create an intense spin-Hall field which in
turns interacts with the ferromagnetic layer of the MRAM through the mechanism
of spin orbit torque. The strong spin-Hall field leads to an infinitesimally
small switching time of the MRAM. Our proposed MRAM is thus a better
alternative to the conventional ferromagnetic/spin-Hall effect bi-layers MRAM
for the reason that the switching time can be varied with ease, which is
unfeasible in the later. Concisely, not only that this work signals a
possibility to design an ultra-fast MRAM, but it also suggests a model to
fabricate a tunable switching time MRAM.
