PORTLAND, Ore. Naval Research Laboratory (NRL) scientists will next month describe a technique that could bring next-generation spintronicssilicon semiconductors that encode bits based on the spin of individual electronsa step closer.
They said the enabling technology, the injection of spin-polarized electrons into silicon semiconductors, was achieved using a ferromagnetic metal/tunnel barrier contact.
"Our demonstration showed a 30 percent polarization of the injected electrons, which is not bad considering that polarizaiton of electrons in magnetic metals is about 45 percent," said lead scientist Berend Jonker. "Now we want to build an electronic detector,
rather than use an LED, as the next step toward silicon spintronics."
Spintronics has been widely recognized as a critical technologyand has been listed in the International Technology Roadmap for Semiconductors as a "difficult challenge" for a "post-CMOS" era beyond the 32-nanometer node. If the NRL technique pans out, spintronics could be inserted into the standard silicon CMOS processes using ferromagnetic materials similar to those already used for magnetic random access memory.
Most other spintronics researchers are resorting gallium arsenide, a material that cannot be integrated like CMOS, or even more exotic materials such as chromium-doped indium oxide.
A few groups have described promising techniques for injecting spin-polarized electrons into silicon, for instance by using high-k dielectrics, but the NRL scientists are the first to report progress with a specific technique compatible with standard CMOS processing techniques.
The NRL scientists claim to have injected electrons through a ferromagnetic film over a high-k aluminum oxide dielectric. Specifically, they formed an iron/aluminum oxide tunnel barrier contact over a light-emitting diode built from layers of n-doped silicon over a silicon-oxide insulator over p-doped silicon.
Despite the weak electroluminescence of a silicon LED, the resulting circularly polarized light confirmed the injection of spin-polarized electrons.