Dawon Kahng
Dawon Kahng (1931-1992) was a Korean-American electrical engineer and physicist at Bell Labs who, with Mohamed Atalla, built the first working MOSFET in 1959, and who later, with Simon Sze, proposed the floating-gate memory transistor that is the basis of flash memory. These two inventions bracket the story of modern microelectronics: the first gave the world the transistor that makes up almost all digital chips, and the second gave that transistor a memory, so that it could retain data without power. Kahng is therefore one of the most consequential engineers of the second half of the 20th century, even though his name is much less well known than the products of his inventions.
He was born in Seoul and educated in Korea and the United States. Kahng studied physics at Seoul National University, moved to the United States, and earned a doctorate in electrical engineering at Ohio State University in 1959. He joined Bell Labs the same year, in a group working on silicon surfaces and devices. There he worked with Atalla, whose oxidation process had produced a stable silicon dioxide layer on silicon. Kahng's contribution was to turn the surface insight into a working device, shaping the structure and fabricating the first examples, which used an oxide-insulated gate over a silicon channel. The results were presented in 1960 and published that year, and a patent on the structure issued in the following years.
The floating-gate idea of 1967 added a second, separate gate. Kahng and Simon Sze, also at Bell Labs, described a MOSFET with an extra conducting layer completely surrounded by insulating oxide, positioned between the control gate and the channel. Charge placed on this floating gate stays there, because the oxide around it is a very good insulator, and its presence shifts the voltage at which the transistor turns on. Reading the transistor's behavior therefore reveals whether a bit is stored. Their description set out the principle of non-volatile semiconductor memory. The practical devices followed later, as erasable programmable memory (EPROM), electrically erasable memory (EEPROM) and then flash memory, which was invented and developed by Fujio Masuoka at Toshiba and others in the early 1980s.
Honors came mostly later. Atalla and Kahng were awarded the Franklin Institute's Stuart Ballantine Medal in 1975 for their work on the MOSFET, and Kahng's patents covered several device types beyond the MOSFET, including work on metal-semiconductor diodes. In 1988 he became the founding president of the NEC Research Institute in Princeton, New Jersey. He died in 1992 following surgery, at the age of 61, before the flash memory he anticipated had become a common product.
A common error is to credit him with inventing flash memory itself. His 1967 contribution is better described as the floating-gate memory principle that flash builds on, with many later inventions needed to make electrically erasable blocks, dense NAND arrays and multi-level cells. Another error is to give Kahng or Atalla sole credit for the MOSFET; it was a joint invention, and field-effect ideas had been proposed decades earlier, though no one had built a practical version. Finally, because his name is less familiar, some summaries leave him out entirely or list him only as an assistant, which understates his role.
Modern relevance is hard to overstate. The floating-gate cell, in various forms, stores data in solid-state drives, memory cards, USB sticks and phones, and the MOSFET structure he helped create is the dominant transistor in processors and memory.
Read Dawon Kahng as the engineer who built the transistor that powers computation and then taught it to remember: the MOSFET of 1959 and the floating gate of 1967 are the two halves of the digital chip.