Nanowire experts at the National Institute of Standards and Technology (NIST) have developed a kind of UV LED. Because of the special type of shell, its light intensity is five times higher than that produced by the same kind of LED with simpler shell design.
UV LED is used in more and more applications, such as polymer curing, water purification and medical disinfection. Micro LED is also the focus of visual display. NIST staff are experimenting with nanowire-based LEDs for scanning probe tips for electronic and biological applications.
This new type of LED with higher light intensity is the result of NIST's expertise in manufacturing high quality GaN nanowires. Recently, researchers have been experimenting with nanowire cores made of silicon-doped GaN with additional electrons surrounded by magnesium-doped GaN shells with additional electron-bound holes.
The light produced by the LED is attributed to the recombination of electrons and holes injected into the shell. The new LED adds a small amount of aluminium to the shell, which reduces the loss caused by electron spillover and light re-absorption.
As reported i n the Journal Nanotechnology, the new LED is made of nanowires with p-i-n structure. The three-layer design injects electrons and holes into nanowires. The addition of aluminium helps to confine electrons to the core of nanowires and increase electroluminescence by five times.
"The role of aluminium is to introduce current asymmetry and prevent electrons from flowing into the shell. Although this reduces efficiency, electrons and holes can be confined to the core of nanowires." First author Matt Brubaker said.
The nanowires have a structure of about 440 nm in length and a shell thickness of about 40 nm. The final LED, including the case, is almost 10 times larger. The researchers found that the amount of aluminium added to the fabrication structure depends on the nanowire diameter.
Research leader Kris Bertness said that at least two companies were developing nanowire-based Miro LEDs, and NIST signed a cooperative R&D agreement with one of them to develop dopants and structural characterization methods. Researchers have had preliminary discussions with Scanning Probe Inc. on the use of NIST's LED technology, and NIST plans to show prototype LEDs soon.