Elias Burstein, one of the pioneers in the optical physics of solids, whose research into the photoionization of impurities in silicon helped pave the way for the development of silicon semiconductors, died June 17 at his home in Bryn Mawr, Pa. He was 99. His family confirmed his death.
Mr. Burstein, a physicist, worked for more than seven decades in his field, much of the time as a professor at the University of Pennsylvania. He was one of the first scientists to use lasers to do research on semiconductors and insulators. He held patents for a method to introduce impurities into the otherwise stable element silicon, increasing its semiconducting capacity.