SEMICONDUCTORS ARE THE KEY to modern electronics these materials are electrical conductors which are nearly insulators Unlike metals only a few of their electrons roam free, while others hop from atom to atom leaving “holes” which act like positive charges moving the opposite way Adding impurities to semiconductors, a process called doping, changes the way they conduct, allowing solid structures to be created in which electrons can be controlled electrically silicon is a semiconductor that has been used in components since the earliest days of radio. It is now the mainstay of electronics. In the early 1940s, however, it was the rare element germanium that seemed more promising for a better radar detectors. By 1945 it was being used in attempts to make a semiconductor device that would amplify (pp. 38-39)