Researchers Develop Silicon Device Responsive to Infrared Light
7 January 2014
An international team of researchers has developed a new system responsive to a wide range of infrared light using silicon, successfully eliminating many obstacles encountered in previous attempts in the field.
The system works at room temperature and produces a broad infrared response, researcher Tonio Buonassisi explained. It has atoms of gold incorporated into the surface of the silicon's crystal in a way that does not interfere with the material's original structure. A key benefit is that the system allows the use of silicon, a common semiconductor which is relatively cheap, easy to process and widely distributed.
For the purposes of the experiment, the researchers implanted gold into the top hundred nanometers of silicon and melted the surface for a few nanoseconds with a laser. The team observed how silicon atoms recrystalize into a nearly perfect lattice, with gold atoms having no time to escape before being caught in the lattice.
The material contained about 1% gold, or over 100 times more than silicon's solubility limit. Under certain conditions, however, materials can surpass their conventional solubility limits, entering a state known as supersaturated solution. In such conditions, the new processing approach produces a layer of silicon supersaturated with gold atoms.
This experiment is the first demonstration that the system can work with gold as the added material and can deliver broadband infrared response in silicon at room temperature, Buonassisi said. The approach could be used for infrared imaging systems, however its efficiency may not be adequate enough for use in silicon cells. Still, this laser processing method could be applicable to different materials that would be suitable for solar cells production, he added.
Funding for the research came from the US Army Research Office, the National Science Foundation and the US Department of Energy, together with the MIT-KFUPM Center for Clean Water and Energy, a joint project of MIT and the King Fahd University of Petroleum and Mining.