AsianScientist (Sep. 3, 2014) – Scientists have devised a method that allows them to increase the spin Hall angle by 40 fold in the commonly used semiconductor material gallium arsenide (GaAs) even at room temperature, matching the performance of more expensive heavy metal spin charge converters. This research has been published in the journal Nature Materials.
Spintronics is an emerging technology with applications in next generation semiconductors and memory storage devices. “Spintronics” is a portmanteau word reflecting the fact that the technology makes use of the spin of the electrons, rather than the current generated by the flow of electrons as with conventional electronics.
Although promising, the field of spintronics has been limited by the difficulty of controlling the spin Hall effect, particularly in light metal materials. In the present study, corresponding author Dr. Hidekazu Kurebayashi from the Precursory Research for Embryonic Science and Technology (PRESTO) at the Japan Science and Technology Agency (JST) and his team have demonstrated a technique of manipulating the spin Hall angle in GaAs.
The key to the research team’s success was exploiting a feature of GaAs known as intervalley transition. Their theoretical calculations showed that valleys exist in the conduction band of GaAs, each with its own spin-orbit coupling. Applying an external electrical force enables the transition from one valley to the other, which in turn affects the strength of the spin Hall effect.
By controlling electron populations in different valleys, the researchers were able to manipulate the spin Hall angle from 0.0005 to 0.02. This 40 fold change in angle has not been achieved in GaAs before, and is comparable to the change observed using the heavy metal platinum, the current gold standard for spin charge converters.
The finding that intervalley transitions can be used to modulate the spin Hall angle paves the way for more efficient and cheaper spintronics materials. In particular, subsituting Ga or As with materials like aluminum, which is known to increase the difference between valleys, is a promising method for pushing the technology further.
The article can be found at: Okamoto et al. (2014) Electric Control of the Spin Hall Effect by Intervalley Transitions.
——-
Copyright: Asian Scientist Magazine; Photo: Johannes Gutenberg University Mainz.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.
