UC Davis researchers have developed a new switching device made of half-metals¹

that possess spin polarization of 100% at the Fermi energy. These switching devices are modifications of heavily doped p-n junctions where a half-metal is sandwiched between the p- and the n-region of a p-n junction. The spin degree of freedom possessed by the half-metals adds another control of the current in the functions of p-n junctions.

Characteristics of the new devices include:

• 100% spin polarization at the Fermi energy, which differs from conventional ferromagnetic metals.
• A current/voltage curve (I-V) curve of the device shows sawtooth form obtained by biasing the half-metallic region with respect to the p- or n-region.
• The devices take advantage of the current silicon and III-V semiconductor technologies, and are composed of half-metals grown on both silicon, and III-V semiconductors, respectively with close matching lattice constants.

Applications include but are not limited to:

• Switching devices made of a single device. The output current can be switched on and off by applying bias between the half-metal region and either the p- or the n-region.
• Spin filters to produce spin-polarized current as only electrons with one spin direction can pass through the half-metal region.
• Giant magnetoresistance devices for computer chips made from stacking the device. A Magnetic field reverses the spins in one stacking layer with respect to a neighboring layer, effectively blocking the current due to the 100% spin polarizations at the Fermi energies in neighboring layers. As the output current changes from a finite value to zero, it serves as ideal ‘1’ and ‘0’ codes.

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¹Half-metals with simple zinc-blende crystal structure are a new class of materials. They have been grown in thin-film forms. They are compounds made of transition metal elements and pnicitdes or carbides, such CrAs. In these compounds, electrons having up spin show metallic behavior while electrons with opposite spin direction exhibit semiconducting properties.

File Number: 11336 

Web site: http://techtransfer.universityofcalifornia.edu/...