Russell Ohl was an American solid-state physicist who discovered the P-N barrier in silicon in 1940 while working at Bell Labs. The P-N junction was to play a crucial role in the ultimate development of the transistor and the solar cell. While experimenting with crystal growth, he noticed that the amount of current changed when the crystal was held under an incandescent lamp on the desk in the room. Ohl realized that it was in fact light shining on the crystal that caused the small current to flow. This principle was the breakthrough that led to the invention of the first transistor.

Russell Ohl’s specialized area of research was into the behavior of certain types of crystals. He worked on materials research in the 1930’s at AT&T's Bell Labs’ Holmdel facility, investigating diode detectors suitable for high-frequency wireless, broadcasting, and military radar. His work was only understood by a handful of scientists in the organization, one of whom was Dr. Walter Brattain (one of the trio who invented the germanium bipolar transistor in 1947, and who would be awarded the Nobel Prize for Physics in 1956).

Ohl, in 1939, discovered the PN barrier (or as it became known, the “P–N junction”). At the time hardly anyone knew anything about the impurities within these crystals, but Russell Ohl discovered the mechanism by which it worked. It was the impurities which made some sections more resistant to electrical flow than others, and thus it was the "barrier" between these areas of different purity that made the crystal work. Ohl later found that super-purifying germanium was the key to making repeatable and usable semiconductor material for diodes. All diodes (incl. LEDs, laser diodes etc) are descendants of Ohl's work. His work with diodes led him later to develop the first silicon solar cells.

Sources

• Institute of Electrical and Electronics Engineers, Inc., Russell Ohl, Accessed 15 October 2008.
• Wikipedia Contributors, Russell Ohl, Wikipedia, Accessed 15 October 2008.
• Cleveland, Cutler (Lead Author); Peter Saundry (Topic Editor). 2007. "Ohl, Russell." In: Encyclopedia of Earth. Eds. Cutler J. Cleveland (Washington, D.C.: Environmental Information Coalition, National Council for Science and the Environment). [Published in the Encyclopedia of Earth March 19, 2007; Retrieved October 18, 2009].