ABSTRACT
Driven by the need for rectifiers in radar systems, researchers attempted to improve the quality of semiconductor materials. At Bell Labs, Russel Ohl and Jack Scaff purified silicon by melting and recrystallizing ingots (Riordan and Hoddeson, 1997). They noticed there were two types of materials, now called n-type and p-type. In an n-type semiconductor, the mobile charge carriers are electrons. In p-type material, the carriers are missing electrons, or “holes.” In 1939, a technician cut a crystal such that it contained a p-n junction, inadvertently making the world’s first solar cell.
