Transistor
The transistor is the fundamental building block of modern electronic devices, and is ubiquitous in modern electronic systems. Julius Edgar Lilienfeld patented a field-effect transistor in 1926 but it was not possible to actually construct a working device at that time. The first practically implemented device was a point-contact transistor invented in 1947 by American physicists John Bardeen, Walter Brattain, and William Shockley. The transistor revolutionized the field of electronics, and paved the way for smaller and cheaper radios, calculators, and computers, among other things. The transistor is on the list of IEEE milestones in electronics, and Bardeen, Brattain, and Shockley shared the 1956 Nobel Prize in Physics for their achievement.
William Gardner Pfann
Pfann was involved in William Shockley's efforts with Bell Labs to use semiconductors to make devices to replace vacuum tubes. The early efforts used germanium. They made high back-voltage germanium rectifiers in 1945. Pfann devised one of the first point-contact transistors: "Specifically, W.G. Pfann had modified the Western Electric 1N26 shielded point-contact (silicon) diode to include two spring-loaded cat whisker point contacts, making a three-electrode configuration with good electrical amplifying properties. This configuration became known at the Type A transistor." He and Walter Brattain developed the process of "forming" these transistors to make them more uniform. 
Pfann also invented a method of bonding fine gold wires to germanium that made the device functional. "The quiet, unassuming man grew steadily in everyone's esteem as he made one valuable contribution after another to the semiconductor research effort."