Scientists develop novel multi-color light-emitting diodes

May 18, 2005

A team of University of California scientists at Los Alamos National Laboratory have developed the first completely inorganic, multi-color light-emitting diodes (LEDs) based on colloidal quantum dots encapsulated in a gallium nitride (GaN) semiconductor. The work represents a new "hybrid" approach to the development of solid-state lighting. Solid-state lighting offers the advantages of reduced operating expenses, lower energy consumption and more reliable performance.

In research published in the current issue of the scientific journal Nano Letters, the team reports on the first successful demonstration of electroluminescence from an all-inorganic, nanocrystal-based architecture where semiconductor nanocrystals are incorporated into a p-n junction formed from semiconducting GaN injection layers. The new LEDs utilize a novel type of color-selectable nanoemitters, colloidal quantum dots, and makes use of emerging GaN manufacturing technologies.

According to Klimov, who leads the nanocrystal-LED research effort, "numerous technologies could benefit from energy efficient, color-selectable solid-state lighting sources ranging from automotive and aircraft instrument displays to traffic signals and computer displays. Semiconductor nanocrystals, known also as quantum dots, are attractive nanoscale light emitters that combine size-controlled emission colors and high emission efficiencies with chemical flexibility and excellent photostability. The use of nanocrystals in light-emitting technologies has, however, always been hindered by the difficulty of making direct electrical connections to the nanocrystals. By putting the quantum dots between GaN injection layers, we've gotten around this difficulty."

The secret to making the electrical connection to the quantum dots is the use of a technique developed at Los Alamos by Mark Hoffbauer and his team that utilizes a beam of energetic, neutral nitrogen atoms for growing GaN films. The technique, called ENABLE (for Energetic Neutral Atom Beam Lithography/Epitaxy), allows for the low-temperature encapsulation of nanocrystals in semiconducting GaN without adversely affecting their luminescence properties. By encapsulating one nanocrystal layer or two layers of nanocrystals of different sizes, the researchers have demonstrated that their LEDs can emit light of either a single color or two different colors. The two color-operation regime is an important step toward creating devices that produce white light.

The development of the multicolor LEDs is the result of a collaboration between two Laboratory research groups: Klimov's quantum-dot team and Hoffbauer's team developing advanced nanoscale processing technologies. Laboratory researchers critical to the project's success also include Alexander Mueller, Melissa Petruska, Marc Achermann, Donald Werder, and Elshan Akhadov. Daniel Koleske of Sandia National Laboratories provided the GaN substrates used for the LED structures.

The Los Alamos Laboratory-Directed Research and Development (LDRD) program provided funding for the Los Alamos work as an Exploratory Research (ER) project. The research fits into a broader area of expertise that Los Alamos National Laboratory maintains in the field of nanotechnology in general, and quantum dot research in particular.

Source: Los Alamos National Laboratory

Explore further: Google eyes nanoparticle platform as part of health rethink

add to favorites email to friend print save as pdf

Related Stories

3-D X-Ray Images of Nanoparticles

Dec 11, 2006

Using a new x-ray microscope that can look at nanomaterials in three dimensions, an international research team has produced the first detailed atomic structure of a core-shell nanoparticle.

Recommended for you

DNA nanoswitches reveal how life's molecules connect

22 hours ago

A complex interplay of molecular components governs almost all aspects of biological sciences - healthy organism development, disease progression, and drug efficacy are all dependent on the way life's molecules ...

Holes in valence bands of nanodiamonds discovered

Jan 28, 2015

Nanodiamonds are tiny crystals only a few nanometers in size. While they possess the crystalline structure of diamonds, their properties diverge considerably from those of their big brothers, because their ...

Demystifying nanocrystal solar cells

Jan 28, 2015

ETH researchers have developed a comprehensive model to explain how electrons flow inside new types of solar cells made of tiny crystals. The model allows for a better understanding of such cells and may ...

User comments : 0

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.