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 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.
Source: National Institute of Standards and Technology (NIST)
Related stories:
New fabrication technique yields nanoscale UV LEDs
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.
Nanosys Announces Issued Patent Covering Fundamental Nanowire Heterostructures
Nanosys have announced the issuance of U.S. Patent No. 6,882,051 (the '051 patent) entitled "Nanowires, nanostructures and devices fabricated therefrom," by the U.S. Patent and Trademark Office. This patent, exclusively licensed from the Regents of the University of California, covers fundamental compositions of matter and methods for creating novel nanowire heterostructures in which the composition changes longitudinally along a wire's length and/or coaxially about its width. This technology covers a broad variety of devices including Field Effect Transistors (FET), light emitting devices including Light Emitting Diodes (LEDs) and nanolasers, solar cells, thermoelectric devices, optical detectors, and chemical and biological sensors.
Advance brings low-cost, bright LED lighting closer to reality
Researchers at Purdue University have overcome a major obstacle in reducing the cost of "solid state lighting," a technology that could cut electricity consumption by 10 percent if widely adopted.
Industrial dye holds the key to advancing spintronics
Commonly used industrial dyes hold the key to advancing the new science of 'spintronics', say researchers working on a new a £2.5 million study.
Nanotech: Hot Technology Gets a Cool Down
It’s the hottest technology – featherweight laptops that feature rapid response, crisp graphics and operate complex computer games; slim cell phones with Web-browsing capabilities, store high resolution photos and keep track of our lives; credit card-sized MP3 players that store thousands of songs and hours of videos.
New, flexible computers use displays with any shape
The shape of things to come in the computer world will be anything but flat, predicts Queen's University Computing professor Roel Vertegaal, who is now developing prototypes of these new "non-planar" devices in his Human Media Laboratory.
Measuring in 3-D
Today, complex optical free-form geometries are used primarily in car headlamps and in optics for cameras and digital projectors. These optical components are expensive to manufacture and to test. At Hannover-Messe on April 21-25, scientists from the Fraunhofer Institute for Applied Optics and Precision Engineering IOF in Jena will be presenting the 3-D measuring system LensShape, which renders the manufacturing process faster and more cost-effective.
3-D images – cordless and any time
Securing evidence at the scene of a crime, measuring faces for medical applications, taking samples during production – three-dimensional images are in demand everywhere. A handy cordless device now en-ables such images to be prepared rapidly anywhere.
