In a feat that may provide a promising array of applications, from energy efficiency to telecommunications to enhanced imaging, researchers at UC Santa Barbara have created a compound semiconductor of nearly perfect quality with embedded nanostructures containing ordered lines of atoms that can manipulate light energy in the mid-infrared range. More efficient solar cells, less risky and higher resolution biological imaging, and the ability to transmit massive amounts of data at higher speeds are only a few applications that this unique semiconductor will be able to support.
Key to this technology is the use of erbium, a rare earth metal that has the ability to absorb light in the visible as well as infrared wavelength — which is longer and lower frequency wavelength to which the human eye is accustomed — and has been used for years to enhance the performance of silicon in the production of fiber optics. Pairing erbium with the element antimony (Sb), the researchers embedded the resulting compound — erbium antimonide (ErSb) — as semimetallic nanostructures within the semiconducting matrix of gallium antimonide (GaSb).
ErSb, according to Lu, is an ideal material to match with GaSb because of its structural compatibility with its surrounding material, allowing the researchers to embed the nanostructures without interrupting the atomic lattice structure of the semiconducting matrix. The less flawed the crystal lattice structure of a semiconductor is, the more reliable and better performing the device in which it is used will be.
“It’s really a new kind of heterostructure,” said Arthur Gossard, professor in the Materials Department and also in the Department of Electrical and Computer Engineering.
“It’s really a new kind of heterostructure.”Arthur Gossard, professor in the Materials Department and also in the Department of Electrical and Computer Engineering, UC Santa Barbara.
The nanostructures allow the compound semiconductor to absorb a wider spectrum of light due to a phenomenon called surface plasmon resonance, said Lu, and that the effect has potential applications in broad research fields, such as solar cells, medical applications to fight cancer, and in the new field of plasmonics.
Optics and electronics operate on vastly different scales, with electron confinement being possible in spaces far smaller than light waves. Therefore, it has been an ongoing challenge for engineers to create a circuit that can take advantage of the speed and data capacity of photons and the compactness of electronics for information processing.
The highly sought bridge between optics and electronics may be found with this compound semiconductor using surface plasmons, electron oscillations at the surface of a metal excited by light. When light (in this case, infrared) hits the surface of this semiconductor, electrons in the nanostructures begin to resonate — that is, move away from their equilibrium positions and oscillate at the same frequency as the infrared light — preserving the optical information, but shrinking it to a scale that would be compatible with electronic devices.
In the realm of imaging, embedded nanowires of ErSb offer a strong broadband polarization effect, according to Lu, filtering and defining images with infrared and even longer-wavelength terahertz light signatures. This effect can be used to image a variety of materials, including the human body, without the risk posed by the higher energies that emanate from X-rays, for instance. Chemicals such as those found in explosives and some illegal narcotics have unique absorption features in this spectrum region. The researchers have already applied for a patent for these embedded nanowires as a broadband light polarizer.
While infrared and terahertz wavelengths offer much in the way of the kind of information they can provide, the development of instruments that can take full advantage of their range of frequencies is still an emerging field. Lu credits this breakthrough to the collaborative nature of the research on the UCSB campus, which allowed her to merge her materials expertise with the skills of researchers who specialize in infrared and terahertz technology.
This story is reprinted from material from UC Santa Barbara, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.