Diffusion Transistor

A diffusion transistor is any transistor formed by diffusing dopants into a semiconductor substrate. Diffusion transistors include some types of both bipolar junction transistors and field-effect transistors. The diffusion process was developed later than the alloy junction and grown junction processes.

Bell Labs developed the first prototype diffusion transistors in 1954.

Read more about Diffusion Transistor:  Diffused-base Transistor, Double Diffusion, Mesa Transistor, Planar Transistor