The surface-barrier transistor is a type of transistor developed by Philco in 1953 as an improvement to the alloy-junction transistor and the earlier point-contact transistor. Like the modern Schottky transistor, it offered much higher speed than earlier transistors and used metal–semiconductor junctions (instead of semiconductor–semiconductor junctions), but unlike the schottky transistor, both junctions were metal–semiconductor junctions.
It consists of a semiconductor crystal forming the base, into which a pair of wells are etched on opposite sides and electroplated to form the metal emitter and collector surface-barrier contacts.
The surface-barrier transistor became obsolete in the early 1960s with the development of the diffusion transistor.