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 Mat4Rail: EU Research Project on the Railway of the Future
23.02.2018 | Universität Bremen

nachricht Atomic structure of ultrasound material not what anyone expected
21.02.2018 | North Carolina State University

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Attoseconds break into atomic interior

A newly developed laser technology has enabled physicists in the Laboratory for Attosecond Physics (jointly run by LMU Munich and the Max Planck Institute of Quantum Optics) to generate attosecond bursts of high-energy photons of unprecedented intensity. This has made it possible to observe the interaction of multiple photons in a single such pulse with electrons in the inner orbital shell of an atom.

In order to observe the ultrafast electron motion in the inner shells of atoms with short light pulses, the pulses must not only be ultrashort, but very...

Im Focus: Good vibrations feel the force

A group of researchers led by Andrea Cavalleri at the Max Planck Institute for Structure and Dynamics of Matter (MPSD) in Hamburg has demonstrated a new method enabling precise measurements of the interatomic forces that hold crystalline solids together. The paper Probing the Interatomic Potential of Solids by Strong-Field Nonlinear Phononics, published online in Nature, explains how a terahertz-frequency laser pulse can drive very large deformations of the crystal.

By measuring the highly unusual atomic trajectories under extreme electromagnetic transients, the MPSD group could reconstruct how rigid the atomic bonds are...

Im Focus: Developing reliable quantum computers

International research team makes important step on the path to solving certification problems

Quantum computers may one day solve algorithmic problems which even the biggest supercomputers today can’t manage. But how do you test a quantum computer to...

Im Focus: In best circles: First integrated circuit from self-assembled polymer

For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.

In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...

Im Focus: Demonstration of a single molecule piezoelectric effect

Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale

Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on High Temperature Shape Memory Alloys (HTSMAs)

15.02.2018 | Event News

Aachen DC Grid Summit 2018

13.02.2018 | Event News

How Global Climate Policy Can Learn from the Energy Transition

12.02.2018 | Event News

 
Latest News

Basque researchers turn light upside down

23.02.2018 | Physics and Astronomy

Finnish research group discovers a new immune system regulator

23.02.2018 | Health and Medicine

Attoseconds break into atomic interior

23.02.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>