New fabrication technique yields nanoscale UV LEDs

June 13, 2007
Nanowire LED Micrograph
[Top] Micrograph of a complete nanowire LED with the end contact. The long nanowire (A) is about 110 micrometers long, a shorter nanowire (B) crosses it. The bright circular section is the metal post from which the nanowires are aligned. Credit: NIST

Researchers at the National Institute of Standards and Technology, in collaboration with scientists from the University of Maryland and Howard University, have developed a technique to create tiny, highly efficient light-emitting diodes (LEDs) from nanowires.

As described in a recent paper, the fabricated LEDs emit ultraviolet light—a key wavelength range required for many light-based nanotechnologies, including data storage—and the assembly technique is well-suited for scaling to commercial production.

Light-based nanoscale devices, such as LEDs, could be important building blocks for a new generation of ultracompact, inexpensive technologies, including sensors and optical communications devices. Ultraviolet LEDs are particularly important for data-storage and biological sensing devices, such as detectors for airborne pathogens. Nanowires made of a particular class of semiconductors that includes aluminum nitride, gallium nitride and indium nitride are the most promising candidates for nanoscale LEDs. But, says NIST researcher Abhishek Motayed, "The current nanowire LEDs are created using tedious nanowire manipulation methods and one-by-one fabrication techniques, which makes them unsuitable for commercial realization."

The NIST team used batch fabrication techniques, such as photolithography (printing a pattern into a material using light, similar to photography), wet etching and metal deposition. They aligned the nanowires using an electric field, eliminating the delicate and time-consuming task of placing each nanowire separately.

A key feature of the new nanowire LEDs is that they are made from a single compound, gallium nitride (GaN). Each LED consists of an "n-type" GaN nanowire placed on the surface of a "p-type" GaN thin film. "N-type" and "p-type" refer to semiconductors with, respectively, an abundance of electrons and an abundance of positively charged electron vacancies called holes. P-n junctions made from the same basic compound yield more efficient LEDs than those made with different compounds, and so can operate at lower power.

When the proper voltage is applied to the junction, it emits light with a peak wavelength of 365 nanometers, which falls squarely in the ultraviolet range. The group produced and tested more than 40 of these LEDs; all showed very similar emission properties. They also displayed excellent thermal stability—withstanding temperatures up to 750 degrees Celsius—and operational stability, showing no signs of deterioration even after two continuous hours of operation at room temperature. These properties indicate that this LED production method yields reliable, stable devices. The researchers say their method could be used to fabricate other nanowire structures as well as applications requiring a large area of nanoscale light sources.

Citation: A. Motayed, A. Davydov, M. He, S. N. Mohammed and J. Melngailis. 365 nm operation of n-nanowire/p-gallium nitride homojunction light emitting diodes. Applied Physics Letters 90, 183120 (2007)

Source: National Institute of Standards and Technology

Explore further: New LEDs may offer better way to clean water in remote areas

Related Stories

Cheaper LEDs from breakthrough in ZnO nanowire research

January 3, 2007

Engineers at UC San Diego have synthesized a long-sought semiconducting material that may pave the way for an inexpensive new kind of light emitting diode (LED) that could compete with today's widely used gallium nitride ...

New Fabrication Technique Yields Nanoscale UV LEDs

May 25, 2007

Researchers at the National Institute of Standards and Technology (NIST), in collaboration with scientists from the University of Maryland and Howard University, have developed a technique to create tiny, highly efficient ...

Recommended for you

New aspect of atom mimicry for nanotechnology applications

December 2, 2016

In nanotechnology control is key. Control over the arrangements and distances between nanoparticles can allow tailored interaction strengths so that properties can be harnessed in devices such as plasmonic sensors. Now researchers ...

Engineers create prototype chip just three atoms thick

November 29, 2016

For more than 50 years, silicon chipmakers have devised inventive ways to switch electricity on and off, generating the digital ones and zeroes that encode words, pictures, movies and other forms of data.

Nanotechnology a 'green' approach to treating liver cancer

November 29, 2016

According to the American Cancer Society, more than 700,000 new cases of liver cancer are diagnosed worldwide each year. Currently, the only cure for the disease is to surgically remove the cancerous part of the liver or ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.