Overview

Today's silicon planar, epitaxial, bipolar junction transistors are but distant cousins of the early transistors invented at Bell Labs. Transistors have been the subject of hundreds of millions of dollars worth of research over the years, yet today we can buy them for pennies. As with the early development of the Internet by the U.S. Defense Advanced Research Projects Agency (DARPA), so it was with the support of the U.S. Department of Defense, particularly by the Air Force, that fueled the early R&D work into both the transistor and the integrated circuit. Airplanes, rockets, and missiles have payload, weight, and reliability concerns, which solid-state electronics helped improve dramatically. The Cold War was a propelling factor in this advance for the U.S. military, paralleled by the race to the moon and into space by NASA.

It is interesting to note that the earliest transistors were germanium (Ge) point-contact and mesa PNP types, which suffered from severe leakage, low resistance, and temperature drift, among other things. One recurring problem was that impurities seemed to settle on the surface of the chip (surface states) or at its junctions, causing the intended design specifications to shift unpredictably. Another more baffling question was why germanium reportedly turned from N-type to P-type material when it was heated, then allowed to cool. Then there were the persistently poor yield problems, which plagued transistor manufacturers for years. In some cases, manufacturers would get as little as one working transistor per wafer not a very efficient or profitable situation.