I spoke with EE's involved with tunnel diode in the early 60's.They told me of their struggles. TD's were going to be the great savior... except that is was hard to make a run of them that had consistent characteristics! The mix was variable... Somewere used for low level microwave oscillators, I had a few boxes from NSA that used them as check sources. Narrow band amplifiers were popular in the microwave world using circulators as signal separation devices, I have an Aertech 8.6-9.4 GHz Tunnel Diode Amplifier box. Even some high speed gates were made. Just couldnt make enough the same to do large volume production. The tunnel diode, or IIRC the Esaki diode, was largely a curiosity. Good I guess in some Tek circuits, but even they struggled, I think, to get consistency. I think I have some Tektronix "Diode Rise Time Fixtures" around that Tek made for testing and sorting diodes like this.
Jeff KruthIn a message dated 2/18/2021 4:55:02 PM Eastern Standard Time, firstname.lastname@example.org writes: My understanding is that by the 1970's or so, TD's were obsolete because most of the practical circuits that used them could be done cheaper with modern transistors and IC's.
TD's could do certain things with a bare minimum parts count, but that wasn't important enough, with the parts count (inside of IC's) exploding in other areas.
Also note that many of the interesting apps for TD's involve inductors, but inductors are not cheap.
I could be wrong...