Washington, May 9 : Researchers at Harvard University and their German collaborators have devised a way to fabricate nanowire photonic and electronic integrated circuits.
The researchers insist that their work may hold significant implications for high-volume commercial production.
Although semiconductor nanowires can be easily synthesized in large quantities using inexpensive chemical methods, reliable and controlled strategies for assembling them into functional circuits have posed a major challenge.
But now the research team has come up with a reproducible, high-volume, and low-cost fabrication method for integrating nanowire devices directly onto silicon.
They did so by incorporating spin-on glass technology, used in Silicon integrated circuits manufacturing, and photolithography, transferring a circuit pattern onto a substrate with light.
"Because our fabrication technique is independent of the geometrical arrangement of the nanowires on the substrate, we envision further combining the process with one of the several methods already developed for the controlled placement and alignment of nanowires over large areas. We believe the marriage of these processes will soon provide the necessary control to enable integrated nanowire photonic circuits in a standard manufacturing setting," said Federico Capasso, one of the researchers.
The research team has based the structure of their nanowire devices on a sandwich geometry, wherein a nanowire is placed between the highly conductive substrate, which functions as a common bottom contact, and a top metallic contact, using spin-on glass as a spacer layer to prevent the metal contact from shorting to the substrate.
Such a structure enables the current to be uniformly injected along the length of the nanowires, and the devices can then function as light-emitting diodes, with the colour of light determined by the type of semiconductor nanowire used.
The team have demonstrated the potential scalability of their technique by fabricating hundreds of nanoscale ultraviolet light-emitting diodes, using zinc oxide nanowires on a silicon wafer.
The researchers say that the fact that nanowires can be made of materials commonly used in electronics and photonics goes to show that they hold great promise for integrating efficient light emitters, from ultraviolet to infrared, with silicon technology.
The team plans to further refine their novel method with an aim towards electrically contacting nanowires over entire wafers.
"Such an advance could lead to the development of a completely new class of integrated circuits, such as large arrays of ultra-small nanoscale lasers that could be designed as high-density optical interconnects or be used for on-chip chemical sensing," said Professor Carsten Ronning of the University of Jena.
The new study appears in the journal Nano Letters.