Alloy-junction Transistor

The germanium alloy-junction transistor, or alloy transistor, was an early type of bipolar junction transistor, developed at General Electric and RCA in 1951 as an improvement over the earlier grown-junction transistor.

The usual construction of an alloy-junction transistor is a germanium crystal forming the base, with emitter and collector alloy beads fused on opposite sides. There were several types of improved alloy-junction transistors developed over the years that they were manufactured.

All types of alloy-junction transistors became obsolete in the early 1960s, with the introduction of the planar transistor which could be mass produced easily while alloy-junction transistors had to be made individually. The first germanium planar transistors had much worse characteristics than alloy-junction germanium transistors of the period, but as they could be mass produced and alloy-junction transistors could not, they cost much less and the characteristics of planar transistors improved very rapidly, quickly exceeding those of all earlier Germanium transistors.