US team sheds light on semiconductor processing
Theory shows how adding light can stamp out defects for better solar panels and LED bulbs
University of Utah materials science and engineering associate professor Mike Scarpulla and senior scientist Kirstin Alberi of the National Renewable Energy Laboratory in Golden, Colorado, have developed a theory that adding light during semiconductor manufacturing can reduce defects and potentially make more efficient solar cells or brighter LEDs.
Scarpulla and Alberi reported their findings in a paper titled 'Suppression of Compensating Native Defect Formation During Semiconductor Processing Via Excess Carriers' published June 16 in the journal, Scientific Reports. The research was funded by grants from the US Department of Energy Office of Basic Energy Sciences.
The theory developed by Scarpulla and Alberi is most interesting for compound semiconductors such as GaAs, CdTe, and GaN which are more susceptible to defects in the material at an atomic scale.
The team discovered that if you add light while firing the material in a furnace at high temperatures, the light generates extra electrons that can change the composition of the material.
For nearly a century, researchers have usually assumed that the numbers of these defects in semiconductors were uniquely defined by the temperature and pressure during processing. "We worked out a complete theory that couples light into that problem," Scarpulla says.
"We ran simulations of what happens," Scarpulla says. "If you put a piece of a semiconductor in a furnace in the dark, you would get one set of properties from it. But when you shine light on it in the furnace, it turns out you suppress these more problematic defects. We think it may allow us to get around some tricky problems with certain materials that have prevented their use for decades. The exciting work is in the future though - actually testing these predictions to make better devices."
The team is working to apply their theory to as many semiconductors as possible and testing the real world results. For example, the team believes this could improve the efficiency of solar panels that use thin films of CdTe and even those made from silicon.
