Researchers at the Korea Institute of Science and Technology (KIST) in Seoul have created a transistor that is switched by magnetism, rather than electricity. This could lead to computer chips that can be quickly and easily reprogrammed with software, allowing for computers and gadgets that “mutate” depending on your computational needs.
This magnetic transistor is fashioned out of indium antimonide (InSb, pictured above), a narrow-gap semiconductor that isn’t usually associated with computer chips. The KIST researchers sandwiched p- and n-doped InSb together, creating something like a magnetic bridge. The n-type InSb has excess electrons, and the p-type has a bunch of holes that the electrons could neatly fit into. When magnetism is applied the electrons are sucked down into the holes, allowing current to flow across the bridge, effectively turning the switch on (pictured below).
The switch remains turned on until the magnetic field is actively flipped — unlike electronic transistors, which require a constant flow of electricity. In theory this could lead to computer chips that consume less power, and chips with circuitry that can be altered on the fly. Instead of computer chips having dedicated transistors for dozens of different instructions and functions, you might just have a few programmable blocks that can be switched from video decoding, to audio processing, to floating point math. It’s a bit like an FPGA – field-programmable gate array but more readily programmable — and perhaps more power efficient, too.
There are caveats, of course — the most blaring of which is that this isn’t silicon. Indium antimonide isn’t overly compatible with current chip making processes, which essentially makes this technology a non-starter, unless someone can prove that these magnetic transistors are really, really awesome. Mark Johnson of the Naval Research Laboratory, talking to Nature, says that it might eventually be possible to build similar magnetic bridges out of silicon, however.
The second issue is that each transistor needs an accompanying magnet to turn it on and off — and there isn’t currently an easy way of integrating miniature magnets into a high-density computer chip. There is good progress being made with magnetic tunnel junctions in MRAM, but whether MTJs can be used with these InSb bridges is uncertain. As silicon slowly trundles towards the end of its road, spintronic devices — such as MRAM or this new magnetic logic — could certainly be the next avenue for computing, but it’s still just too early to call.
Research paper: doi:10.1038/nature11817 – “Magnetic-field-controlled reconfigurable semiconductor logic”