Ohl's accidental discovery suggested that vacuum tubes, which were slow to warm up, needed a great deal of power, and were bulky, might be replaced by crystals of silicon and other semiconductors, which did not need to be heated, drew very little current, and were small. Semiconductors are crystalline materials, like silicon and germanium, whose properties of conducting electricity fall between those of conductors (like the copper used in electrical wires) and insulators (like the plastic coatings put on wires).
The military needs of World War II (1939-1945) redirected Brattain's scientific focus for nearly two years, during which he was assigned to study magnetic detection of submarines at the National Defense Research Committee at Columbia University. After the war, he returned to Bell Labs, where he was assigned to a new solid-state research team. Headed by William Shockley, the team also included John Bardeen, a friend of Brattain's brother, Robert. Brattain, with his experimental expertise, and Bardeen, with his theoretical skills, became a formidable research duo.
In December 1947, the efforts of Brattain and Bardeen to develop an amplifier paid off when they successfully collaborated on the first transistor. This half-inch high device—huge by later standards—was called a point-contact transistor. It was crafted by Brattain more or less according to Bardeen's specifications. Although Bardeen had requested two metal contacts separated by the thickness of a sheet of paper, Brattain substituted a single strip of gold foil. After attaching the foil over the point of a plastic triangle, he used a razor blade to create two gold contacts separated by the width of a hair. A spring held the triangle over a crystal of germanium—a hard, metallic, grayish-white element—so that the contacts barely touched the surface. Brattain had placed the crystal itself on a metal plate, which he attached to a source of voltage. The result was the first semiconductor amplifier.
As soon as Brattain turned on the voltage, he observed that when a small current passed through one of the gold contacts, a stronger—or amplified—current emerged from the other contact. When current passed through the contact, electrons left a thin layer along the top of the germanium. Thus, the current created a P-type layer, a layer of material with an abnormally small number o
