John Bardeen and the Point-Contact Transistor

To this day it is not well understood that the bipolar transistor began with John Bardeen and Walter H. Brattain's point-contact transistor. The invention of the point-contact transistor was a momentous event, not only in itself but even more because of the unimaginable revolution in electronics that followed. This revolution, which continues unabated, had a beginning: Bardeen's recognition of minority-carrier injection—that is, his realization that an applied voltage causes valence band holes from the surface region of an n-type semiconductor material near a metal contact to be injected into the bulk of the material. This realization made the semiconductor suddenly important and no longer just an interesting material to study.