Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Zeroing in on the Elusive Green LED

Researchers Discover New Method for Boosting the Light Output of Green LEDs — A Critical Step Toward the Development of LED Televisions and Displays

Researchers at Rensselaer Polytechnic Institute have developed a new method for manufacturing green-colored LEDs with greatly enhanced light output.

The research team, led by Christian Wetzel, professor of physics and the Wellfleet Constellation Professor of Future Chips at Rensselaer, etched a nanoscale pattern at the interface between the LED’s sapphire base and the layer of gallium nitride (GaN) that gives the LED its green color. Overall, the new technique results in green LEDs with significant enhancements in light extraction, internal efficiency, and light output.

The discovery brings Wetzel one step closer to his goal of developing a high-performance, low-cost green LED.

“Green LEDs are proving much more challenging to create than academia and industry ever imagined,” Wetzel said. “Every computer monitor and television produces its picture by using red, blue, and green. We already have powerful, inexpensive red and blue LEDs. Once we develop a similar green LED, it should lead to a new generation of high-performance, energy-efficient display and illumination devices. This new research finding is an important step in the right direction.”

Sapphire is among the least expensive and widely used substrate materials for manufacturing LEDs, so Wetzel’s discovery could hold important implications for the rapidly growing, fast-changing LED industry. He said this new method should also be able to increase the light output of red and blue LEDs.

Results of the study, titled “Defect-reduced green GaInN/GaN light-emitting diode on nanopatterned sapphire,” were published last week in the journal Applied Physics Letters, and are featured in today’s issue of the Virtual Journal of Nanoscale Science & Technology, published by the American Institute of Physics and the American Physical Society. The paper may be viewed online at:

The research program is supported by the U.S. Department of Energy National Energy Technology Laboratory (NETL) Solid-State Lighting Contract of Directed Research, and the National Science Foundation (NSF) Smart Lighting Engineering Research Center (ERC), which is led by Rensselaer.

LED lighting only requires a fraction of the energy required by conventional light bulbs, and LEDs contain none of the toxic heavy metals used in the newer compact fluorescent light bulbs. In general, LEDs are very durable and long-lived.

First discovered in the 1920s, LEDs – light-emitting diodes – are semiconductors that convert electricity into light. When switched on, swarms of electrons pass through the semiconductor material and fall from an area with surplus electrons into an area with a shortage of electrons. As they fall, the electrons jump to a lower orbital and release small amounts of energy. This energy is realized as photons – the most basic unit of light. Unlike conventional light bulbs, LEDs produce almost no heat.

The color of light produced by LEDs depends on the type of semiconductor material it contains. The first LEDs were red, and not long thereafter researchers tweaked their formula and developed some that produced orange light. Years later came blue LEDs, which are frequently used today as blue light sources in mobile phones, CD players, laptop computers, and other electronic devices.

The holy grail of solid-state lighting, however, is a true white LED, Wetzel said. The white LEDs commonly used in novelty lighting applications, such as key chains, auto headlights, and grocery freezers, are actually blue LEDs coated with yellow phosphorus – which adds a step to the manufacturing process and also results in a faux-white illumination with a noticeable bluish tint.

The key to true white LEDs, Wetzel said, is all about green. High-performance red LEDs and blue LEDs exist. Pairing them with a comparable green LED should allow devices to produce every color visible to the human eye – including true white, Wetzel said. Today’s computer monitor and television produces its picture by using red, blue, and green. This means developing a high-performance green LED could therefore likely lead to a new generation of high-performance, energy-efficient display devices.

The problem, however, is that green LEDs are much more difficult to create than anyone anticipated. Wetzel and his research team and investigating how to “close the green gap,” and develop green LEDs that are as powerful as their red or blue counterparts.

Michael Mullaney | EurekAlert!
Further information:

More articles from Physics and Astronomy:

nachricht First results of NSTX-U research operations
26.10.2016 | DOE/Princeton Plasma Physics Laboratory

nachricht Scientists discover particles similar to Majorana fermions
25.10.2016 | Chinese Academy of Sciences Headquarters

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Etching Microstructures with Lasers

Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.

This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...

Im Focus: Light-driven atomic rotations excite magnetic waves

Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion

Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Greater Range and Longer Lifetime

26.10.2016 | Power and Electrical Engineering

VDI presents International Bionic Award of the Schauenburg Foundation

26.10.2016 | Awards Funding

3-D-printed magnets

26.10.2016 | Power and Electrical Engineering

More VideoLinks >>>