The diffusion junction transistor was created by Bell Laboratories in 1954.
The diffusion junction transistor is a transistor which is shaped when the n-type silicon wafer called substrate is presented to p-type and n-type vaporous impurities.
Diffusion is the cycle by which charged particles streams from a higher concentration region to a lower concentration region. The diffusion junction transistors utilize this diffusion method to form the transistor.
In this method, a n-type substrate is put in vaporous acceptor impurities and heated. The acceptor impurities diffuse into the n-type substrate (collector) to form a p-type layer (base) on it.
Consequently, a p-type layer (base) is made on the n-type layer (collector).
The whole framework is presented to the vaporous donor impurities and again heated. The donor impurities diffuse into the p-type layer (base) to form a n-type layer (emitter) on it.
In this manner, a n-type layer (emitter) is made on the p-type layer (base).
Finally, a thin layer of silicon dioxide is become over the whole surface and photoetched, so aluminum contacts can be made for the emitter and base leads.