Morgan Sparks, seen here holding an early transistor in an undated photo, was the former director of Sandia National Laboratories and inventor of the first practical transistor. (AP photo/Courtesy of Sandia National Laboratories)

Morgan Sparks, who led Sandia National Laboratories for almost a decade and invented a semiconductor device that has revolutionized almost every aspect of modern life, has died. He was 91.

Sparks died Saturday at his daughter's home in Fullerton, Calif., Sandia said in a news release.

Sparks worked for 30 years at Bell Laboratories in New Jersey before taking over as director of Sandia in 1972. He served in the post until his retirement in 1981.

Sandia and Bell labs officials said Sparks invented the first practical transistor, a semiconductor device that led to devices such as personal computers, cell phones and DVD players.

Transistors work something like light switches, flipping on and off inside a chip to generate the ones and zeros that store and process information inside a computer.

Sparks joined the Semiconductor Research Group at the New Jersey lab in 1948 just as a group of physicists — John Bardeen, Walter Brattain and William Shockley — were developing the first transistor, an achievement that would later earn the trio a Nobel prize.

Sparks conducted materials science research with the group and worked with fellow team members Shockley and Gordon Teal to help develop the microwatt junction transistor in 1951.

Junction transistors began replacing vacuum tubes in electronic devices such as portable radios. Soon, transistors became essential in electronic computers and their production grew monumentally after the emergence of the microchip in the 1960s.

Sparks was born in 1916 in Pagosa Springs, Colo., and raised in Texas. He earned his bachelor's and master's degrees in chemistry at Rice University before receiving his doctorate in physical chemistry from the University of Illinois in 1943.