III-V-on-Si start-up promises cheaper solar cells
US start-up 4Power is developing III-V-on-silicon multi-junction cells that promise to deliver the performance of conventional compound semiconductor equivalents, but at a fraction of the price.
The fabless company is aiming to commercialize solar cells that were developed by its co-founders, Eugene Fitzgerald from MIT and Steven Ringel from Ohio State University.
Fitzgerald says that the privately-funded company has transferred the fabrication techniques used in research labs to large-volume foundries. These processes will now be optimized, before solar cell products are released for terrestrial and space applications.
4Power is targeting growth on 200 mm silicon substrates. This should initially deliver manufacturing costs that are roughly half of those for conventional III-V cells, thanks to silicon's large substrate sizes and low prices. Fitzgerald expects this margin to increase as volumes go up, and the company transfers to a 300 mm platform late next year.
The co-founders started to develop III-V-on-silicon cells back in 1997, and solved the problems of growth on a foreign substrate over five years ago.
That approach involves deposition of a SiGe layer by solid source MBE, which is graded from silicon to germanium. A thin layer of germanium is then added, along with a GaAs film that is free from anti-phase domains. Switching to MOCVD produces single and multi-junction solar cells.
