Search Menu
Photonics Media Photonics Buyers' Guide Photonics Spectra BioPhotonics EuroPhotonics Vision Spectra Photonics Showcase Photonics ProdSpec Photonics Handbook
More News

First Optoelectronic 3-D Photonic Crystal Developed

Facebook Twitter LinkedIn Email Comments
CHAMPAIGN, Ill., July 25, 2011 — Using an epitaxial approach, the first optoelectronically active 3-D photonic crystal has been demonstrated — an advance that could open new avenues for solar cells, lasers, LEDs, metamaterials and more.

"We've discovered a way to change the three-dimensional structure of a well-established semiconductor material to enable new optical properties, while maintaining its very attractive electrical properties," said research leader Paul Braun, a professor of materials science and engineering and of chemistry at the University of Illinois.

This graphic shows the method for epitaxial growth of 3-D photonic crystals. (Images: Erik Nelson)

Photonic crystals can control or manipulate light in unexpected ways with their unique physical structures. However, previous attempts at making 3-D photonic crystals produced devices that could direct light but that could not turn electricity to light or vice versa.

The Illinois team's photonic crystal has both properties. To create a 3-D photonic crystal that is both electronically and optically active, the researchers started with a template of tiny spheres packed together, then deposited gallium arsenide through the template, filling in the gaps between the spheres.

The GaAs grows as a single crystal from the bottom up, a process called epitaxy. Epitaxy is commonly used in industry to create flat, two-dimensional films of single-crystal semiconductors, but Braun's group developed a way to apply it to an intricate 3-D structure.

"The key discovery here was that we grew single-crystal semiconductor through this complex template," said Braun, who also is affiliated with the Beckman Institute for Advanced Science and Technology and with the Frederick Seitz Materials Research Laboratory at the university. "Gallium arsenide wants to grow as a film on the substrate from the bottom up, but it runs into the template and goes around it. It's almost as though the template is filling up with water. As long as you keep growing GaAs, it keeps filling the template from the bottom up until you reach the top surface."

Using an epitaxial approach, University of Illinois researchers developed a 3-D photonic crystal LED, the first such optoelectronic device.

The epitaxial approach eliminated many of the defects introduced by top-down fabrication methods, a popular pathway for creating 3-D photonic structures. Another advantage was the ease of creating layered heterostructures.

Once the template was full, the researchers removed the spheres, leaving a complex, porous 3-D structure of single-crystal semiconductor. They coated the entire structure with a very thin layer of a semiconductor with a wider bandgap to improve performance and prevent surface recombination.

To test their technique, they built a 3-D photonic crystal LED, the first such working device.

The group currently is working to optimize the structure for specific applications. The LED demonstrates that the concept produces functional devices, but by tweaking the structure or using other semiconductor materials, researchers can improve solar collection or target specific wavelengths for metamaterials applications or low-threshold lasers.

For more information, visit:
Jul 2011
A well controlled thin films technique for growing films with good crystal structure in ultra high vacuum environments at very low deposition rates. Epitaxy methods are well known for the growing of single crystals in which chemical reactions produce thin layers of materials whose lattice structures are identical to that of the substrate on which they are deposited. Some examples are molecular beam epitaxy, liquid phase epitaxy and vapor phase epitaxy. Molecular beam epitaxy is also commonly...
3-D photonic crystal LEDAmericasBasic ScienceBeckman Institute for Advanced Science and TechnologyenergyepitaxyFrederick Seitz Materials Research LaboratoryGaAsgallium arsenidegreen photonicslight sourceslow-threshold lasersmanipulate lightmetamaterialsoptically activeopticsoptoelectronic 3-D photonic crystalPaul BraunResearch & Technologysingle-crystal semiconductorssolar cellsUniversity of IllinoisLEDslasers

back to top
Facebook Twitter Instagram LinkedIn YouTube RSS
©2019 Photonics Media, 100 West St., Pittsfield, MA, 01201 USA,

Photonics Media, Laurin Publishing
x We deliver – right to your inbox. Subscribe FREE to our newsletters.
We use cookies to improve user experience and analyze our website traffic as stated in our Privacy Policy. By using this website, you agree to the use of cookies unless you have disabled them.