MIT Technology review magazine named a 32 yrs old Ethiopian scientist Dr. Solomon Assefa inventor of the year under 35 among other 35 inventors selected by the magazine.
According to the MIT magazine Solomon Assefa selected for his invention of chips that communicate with pulses of light instead of electrical signals could lead to computers that are more power-efficient than today’s best machines and up to 1,000 times as fast. IBM researcher Solomon Assefa has brought this prospect a critical step closer.
Assefa has developed a new way to make a photodetector, a very sensitive device that amplifies optical signals and converts them into electrical signals that can be shuttled around in a microprocessor. Ordinarily, photodetectors are made using a process called chemical vapor deposition. But sticking with this process for chip-to-chip connections would make microprocessor manufacturing prohibitively expensive. Instead, Assefa seeds germanium onto a silicon wafer, and then melts it to achieve the regular crystal structure that makes for a good photodetector material. He has also determined when in the chip manufacturing process the photodetector should be added in order to get the best performance possible without degrading the surrounding electronics.
Assefa can demonstrate the performance of his photodetector in the lab. But before a chip incorporating his creation can be commercialized, he will have to figure out how all the rest of its elements can be integrated efficiently. Making today’s integrated circuits requires hundreds of steps and dozens of lithographic masks, the stencils used to pattern features on chips. “We don’t want to change any of these processes or it really increases the costs,” he says.
The report of this work, entitled “Reinventing Germanium Avalanche Photodetector for Nanophotonic On-chip Optical Interconnects,” by Solomon Assefa, Fengnian Xia, and Yurii Vlasov of IBM’s T.J. Watson Research Center in Yorktown Heights, N.Y. is published in the March 2010 issue of the scientific journal Nature.
About Solomon Assefa
Dr. Solomon Assefa joined the IBM Thomas J. Watson Research Center in 2004. His research interests include Si nanophotonics integration with CMOS for optical communications, ultra-compact and highly efficient photodetectors, avalanche amplification, slow-light engineering for buffering application, low-power optical switches, and electrically-activated photonic-crystal devices for low-power switches/modulators and novel applications including biosensing. He has also explored magnetic random access memory (MRAM) and spin-torque memory device integration.
He received a B.S. degree in physics, as well as B.S. and M.S. degrees in electrical engineering and computer science (EECS) in 2001 from MIT. Then, he received a Ph.D. degree from MIT in June 2004 for his research on novel passive and active photonic-crystal devices on III–V and Si-based platforms. He was born in Addis Ababa, Ethiopia.