Should take everything with a grain of salt. The 1880s patent was just that, a patent. I could patent unicorn saddles doesn't mean they exist. I addressed this is the pt 1 thread.
In 1938 Robert Pohl and Rudolf Hilsch experimented on potassium-bromide crystals with three electrodes at Gottingen University, Germany. They reported amplification of low-frequency (about 1 Hz) signals, but their research did not lead to any applications.
Should take everything with a grain of salt. The 1880s patent was just that, a patent. I could patent unicorn saddles doesn't mean they exist. I addressed this is the pt 1 thread.
In 1938 Robert Pohl and Rudolf Hilsch experimented on potassium-bromide crystals with three electrodes at Gottingen University, Germany. They reported amplification of low-frequency (about 1 Hz) signals, but their research did not lead to any applications.
https://www.computerhistory.org/siliconengine/field-effect-semiconductor-device-concepts-patented/
If we wanted to discuss proof of semiconductors we could go back 100 years. Transistor action was not achieved until December 1947.
https://www.computerhistory.org/siliconengine/invention-of-the-point-contact-transistor/