It became obsolete in the early 1960s with the development of the diffusion transistor.

Bell Labs developed the first prototype diffusion transistors in 1954.

The earliest diffusion transistors were diffused-base transistors.

Diffused-base transistor- first implementation of 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 proposed design would have been built with either point-contact transistors or surface barrier transistors, both likely to be soon outperformed by the then newly invented diffusion transistors.

Further developments included the grown-junction transistor (1951), the surface-barrier transistor (1953), the diffusion transistor, the tetrode transistor, and the pentode transistor.

He helped develop synthetic rubber during World War II, he was involved in early experiments of zone melting, he is credited with devising the method of transistor production yielding diffusion transistors, he produced some of the first solar cells with high efficiency, and he researched polymers and their applications.