Researchers have managed to figure out how to place a crystal lattice of just electrons at the bottom of a silicon quantum well. The first results promise a 1,700 times greater electron mobility than achievable in crystalline silicon and 200 times more than in graphene.
Lead researcher Sergey Kravchenko of Northeastern University in the United States told EETimes that the work is still a long way from useful applications. If researchers do indeed make the expected progress as a result of this publication, he believes the door will be slightly more open for applications by the semiconductor industry.
The current quest focuses on finding the Wigner crystal, predicted in 1934 by Eugene Wigner. With these new samples it should be possible to answer the question whether the Wigner crystal can be made or not. “We now have the techniques that allow us to observe this new state of matter. If it does exist as predicted by Wigner, then one of the most important issues in so-called condensed matter physics has been answered,” Kravchenko said.
The research team hopes that if the results are confirmed, the ultra-high electron mobility will attract researchers from the semiconductor sector to find out how it can actually be applied.
Kravchenko indicates that we must not forget that there are no atoms in the space of the well, only electrons. The research thus yielded so-called electron ‘gas’, since the electrons would normally dance around like molecules in space. Under the right conditions, however, electron gas crystallizes into a crystal lattice with an electron mobility of 2.4 million cm²/Vs. For comparison, silicon has an electron mobility of 1400 cm²/Vs. The electron gas is two-dimensional, which means that the electrons can only move in the plane. They cannot cross each other in the direction perpendicular to the plane.
The researchers built the well from eight layers of metal and silicon compounds containing the 15nm thin quantum well. The aluminum gate on top of the quantum well had a threshold of almost zero volts and the conduction was very sensitive to temperature. The authors hope that others will be able to reproduce their findings. The full publication can be found in Applied Physics Letters.
Wigner crystal Source: Wikipedia