While conventional electronic devices encode information based on the presence or absence of charge, devices based on ‘spintronics’ exploit the property of electron spin instead. This has potential advantages in speed, circuit density and power consumption, but controlling and detecting spins is challenging. A spin field-effect transistor (FET) controls a spin-polarized current flowing between its source and drain contacts using a voltage applied to the gate of the device. However, despite being the subject of much research since it was first proposed in 1990, an experimental realization of a spin FET has been elusive. Now, Joonyeon Chang and colleagues from the Korean Institute of Science and Technology and Sejong University, along with Mark Johnson from the US Naval Research Laboratory, have experimentally demonstrated a spin FET for the first time1.

Fig. 1: The spin precession properties of spintronic devices hold promise for nanoelectronics.

In the researchers' device, spin-polarized electrons are injected from a ferromagnetic source contact into a channel consisting of a two-dimensional electron gas in the semiconductor indium arsenide (InAs). A second ferromagnet is used as the drain contact. In order for electrons to pass through the transistor, the electron spin must align with the direction of magnetization of each contact. But while the electrons travel through the channel, the direction of the spin rotates, or ‘precesses’, under the influence of the gate voltage as a result of a phenomenon called Rashba spin-orbit coupling. The speed of this rotation can be controlled by the gate voltage, allowing the electron spins to be aligned with the drain contact magnetization only at certain gate voltages.

The experimental device fabricated by the research team based on this mechanism produced the signature of a spin FET: a channel conductance that was modulated by the gate voltage. Additional data on channel conductance modulation in the absence of gate effects, and as a function of temperature, confirmed the effect to be due to gate control of electron spin. Modeling of the size and frequency of the conductance modulations also matched the experimental data.

A memory device made using the spin FET would have the advantage of being non-volatile — requiring no power to store data — because the source and drain magnetization directions do not change when the device is unpowered. The spin FET may also be used to combine memory and computing functions, unlike the transistors in today’s computers.