There were several types of improved alloy-junction transistors developed over the years that they were manufactured.

These transistors still had alloy emitters and sometimes alloy collectors like the earlier alloy-junction transistors.

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.

The micro-alloy transistor (MAT) was developed by Philco as an improved type of alloy-junction transistor, it offered much higher speed.

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.

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.

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 paper dealing with avalanche transistors was : the paper describes how to use alloy-junction transistors in the avalanche breakdown region, in order to overcome speed and breakdown voltage limitations which affected the first models of such kind of transistor when used in earlier computer digital circuits.