History
The name bipolar is used because both types of carriers namely hole and
electron are used in the transistor, as opposed to field effect transistor, which is
considered a unipolar device.
Transistor was invented by J. Bardeen (1908 - 1987), W. Shockley (1910-
1989), and W. Brattain (1902 - 1987) in 1948. Fig. 2.1 shows the picture of
three transistor inventors. In 1950 the junction transistor was made using molten
germanium. The bipolar transistors produced in 1950s were typically made with
alloyed junction.
The planar technology developed around 1960 started to use silicon as the
semiconductor material. Today bipolar junction transistor enjoys a large market
but they have been challenged by MOSFETs because of cost, yield, power,
miniaturization, and etc.