Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Materials could make for super LEDs, solar cells, computer chips

03.12.2003


Engineers at Ohio State University have overcome a major barrier in the manufacture of high quality light emitting devices and solar cell materials.


Engineers at Ohio State University have built bright light-emitting diodes (LEDs) on silicon substrates. One such LED is shown here. The new LEDs have a display quality comparable to that of traditional LEDs. Photo courtesy of Ohio State University.



Steven Ringel, professor of electrical engineering, and his colleagues have created special hybrid materials that are virtually defect-free -- an important first step for making ultra-efficient electronics in the future.

The same technology could also lead to faster, less expensive computer chips.


Ringel directs Ohio State’s Electronic Materials and Devices Laboratory, where he and his staff grow thin films of “III-V” semiconductors -- materials made from elements such as gallium and arsenic, which reside in groups III and V of the chemical periodic table.

Because III-V materials absorb and emit light much more efficiently than silicon, these materials could bridge the gap between traditional silicon computer chips and light-related technologies, such as lasers, displays, and fiber optics.

Researchers have tried for years to combine III-V materials with silicon, but only with limited success. Now that Ringel has succeeded in producing the combination with record quality, he has set his sights on a larger goal.

“Ultimately, we’d like to develop materials that will let us integrate many different technologies on a single platform,” Ringel said.

Key to Ringel’s strategy is the idea of a “virtual substrate” -- a generic chip-like surface that would be compatible with many different kinds of technologies, and could easily be tailored to suit different applications.

Ohio State graduate student Ojin Kwon reported the project’s latest results December 2 at the Materials Research Society meeting in Boston. Other coauthors include graduate student John Boeckl, also of Ohio State; and postdoctoral researcher Minjoo Lee, graduate student Arthur Pitera, and professor Eugene Fitzgerald, all of the Massachusetts Institute of Technology.

Ringel’s current materials design consists of a substrate of silicon topped with III-V materials such as gallium and arsenide, with hybrid silicon-germanium layers sandwiched in-between. The substrate is 0.7 millimeters thick, while the gallium arsenide layer is only 3 micrometers -- millionths of a meter -- thick.

Other labs have experimented with III-V materials grown on silicon, but none have been able to reduce defect levels below a critical level that would enable devices like light emitting diodes and solar cells to be achieved, Ringel said.

Defects occur when the thin layers of atoms in a film aren’t lined up properly. Small mismatches between layers rob the material of its ability to transmit electrical charge efficiently.

Ringel and his colleagues grew films of III-V semiconductors with a technique known as molecular beam epitaxy, in which evaporated molecules of a substance settle in thin layers on the surface of the silicon-germanium alloy. They then used techniques such as transmission electron microscopy to search for defects.

Defects are missing or misplaced atoms that trap electrons within the material, Ringel explained. That’s why engineers typically measure the quality of a solar cell material in terms of carrier lifetime -- the length of time an electron can travel freely through a material without falling into a defect.

Other experimental III-V materials grown on silicon have achieved carrier lifetimes of about two nanoseconds, or two billionths of a second. Ringel’s materials have achieved carrier lifetimes in excess of 10 nanoseconds.

The engineers have crafted the III-V material into one-square-inch versions of solar cells in the laboratory, and achieved 17 percent efficiency at converting light to electricity. They have also built bright light-emitting diodes (LEDs) on silicon substrates that have a display quality comparable to that of traditional LEDs.

The next phase in this research will carry Ringel’s materials into space, as part of NASA’s Materials International Space Station Experiment (MISSE). An international partner spacecraft will deliver samples of the materials to the space station so they can be tested and possibly developed for use in future spacecraft.

This work was funded by the Army Research Office and the National Science Foundation.


Contact: Steven Ringel, (614) 292-6904; Ringel.1@osu.edu
Written by Pam Frost Gorder, (614) 292-9475; Gorder.1@osu.edu

Pam Frost Gorder | OSU
Further information:
http://researchnews.osu.edu/archive/35led.htm

More articles from Materials Sciences:

nachricht Glass's off-kilter harmonies
18.01.2017 | University of Texas at Austin, Texas Advanced Computing Center

nachricht Explaining how 2-D materials break at the atomic level
18.01.2017 | Institute for Basic Science

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

Im Focus: How to inflate a hardened concrete shell with a weight of 80 t

At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).

Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

Nothing will happen without batteries making it happen!

05.01.2017 | Event News

 
Latest News

A big nano boost for solar cells

18.01.2017 | Power and Electrical Engineering

Glass's off-kilter harmonies

18.01.2017 | Materials Sciences

Toward a 'smart' patch that automatically delivers insulin when needed

18.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>