https://spectrum.ieee.org/in-memoriam-may-2023 Tanenbaum’s research in the mid-1950s proved that silicon was a better semiconductor material for transistors than germanium, which was commonly used at the time. His discovery paved the way for more efficient transistors critical in technologies that ushered in the Information Age. He began his career in 1952 at Bell Labs, in Murray Hill, N.J., as a researcher in its chemical physics department. Two years later, under the direction of physicist and inventor William Shockley, who at the time worked at Bell Labs, Tanenbaum began investigating whether silicon crystals could be used for transistors. In 1955 he and colleague Ernest Buehler demonstrated the first silicon transistor. Tanenbaum later developed the first gas-diffused silicon transistor, which could amplify and switch signals above 100 megahertz at a switching speed 10 times that of previous silicon transistors. Despite Tanenbaum’s early work on silicon transistors, AT&T did not support further research or advancement of the technology. At the time, Bell Labs was the research arm of AT&T. Although Bell Labs had “a significant technological lead in silicon transistor technology, it stopped doing proper research in the field—partly because it just wasn’t immediately relevant to AT&T’s business—so silicon transistor technology, including the integrated circuit, was done by Intel and Texas Instruments instead,” Tanenbaum said in a 1999 oral history conducted by the IEEE History Center. Tanenbaum instead worked on other new technologies in the decades that followed. In 1962 he was named assistant director of Bell Labs’ metallurgical department. He led the team there that created the first high-field superconducting magnets, which are now used in MRI machines and other medical imaging technologies. Later he helped develop optical fiber and digital telephone switching. Tanenbaum went on to serve as president of AT&T’s New Jersey Bell (now part of Verizon) in the late 1970s and early 1980s. He was appointed president of AT&T Communications in 1984. He retired five years later as AT&T’s vice chairman and chief financial officer. A member of the American Academy of Arts and Sciences, he also was a Fellow of the American Physical Society and a member of the MIT board of trustees. He received a bachelor’s degree in chemistry in 1949 from Johns Hopkins University, in Baltimore, and earned a Ph.D. in physical chemistry from Princeton.