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The transistor was invented some 50 65 years ago, so is it not about time to be able to make transistors or other semiconductors at home?

Would that be possible?

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    \$\begingroup\$ No such discussion could be complete with mention of Jeri Ellsworth's work, for example: youtube.com/watch?v=w_znRopGtbE \$\endgroup\$ Oct 26 '14 at 15:15
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    \$\begingroup\$ possible duplicate of How are integrated circuits fabricated? \$\endgroup\$ Oct 26 '14 at 15:25
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    \$\begingroup\$ @ChrisStratton That's a pretty interesting approach- the silver epoxy in place of metalization is great. This fellow (Claude Paillard) makes professional-looking vacuum triodes by hand here. \$\endgroup\$ Oct 26 '14 at 15:36
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    \$\begingroup\$ Yes, I suspect if one wanted to make parts to use vacum tubes might be more practical. \$\endgroup\$ Oct 26 '14 at 15:40
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It's relatively easy to make some semiconductor devices at home. You can make a diode with a cat's whisker and a galena crystal, or oxidize some copper. Perhaps better in Vf than a silicon diode (but unreliable and low current). CdS is available commercially, so it might be possible to make a photocell or even a crude FET. If you got ahold of high quality commercial wafers it might be possible to make crude (leaky low-gain) transistors and certainly would be possible to make photocells and diodes.

But generally, semiconductor processing involves noxious or explosive chemicals such as silane and arsenic, high temperatures (like 1000°C), vacuum equipment for sputtering, ion implantation, wet equipment for photoresist processing and equipment with expensive optics for photo lithography. None of this stuff has gotten much easier, though you can certainly buy old machinery (eg. on eBay) and try to use it. Probably a really knowledgeable person could get something going for less than the cost of a house in a good urban area. The small scale fabs I know of generally have a full time process engineer to keep the stuff working.

As far as doing things in an informal setting, things have been going the other way in developed countries and it's much more difficult to buy chemicals (most outfits refuse to sell much that's interesting to individuals) than it was 30 or 40 years ago, more bylaws restricting what you can do and so on. Hazmat shipping charges mean that even small amounts are quite costly. People are justifiably afraid that a Superfund site in their neighborhood might depress property values.

Making semis is not inherently a 'clean' process like machining or most types of 3D printing. I don't see it becoming markedly easier in the foreseeable future, though individuals with the specialized knowledge can do some interesting things.

Litigiousness is another detriment- Scientific American's Amateur Scientist column used to have articles on building blindingly powerful CO2 lasers and particle accelerators.

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Sure, people have been making diodes and transistors at home for many years. Google "point-contact diode" and "point-contact transistor". The point-contact transistor was the first kind of transistor ever made. Performance is terrible compared with today's devices, and it can be tricky to even get a beta > 1, but it is do-able.

Kids have been building crystal radio sets with home made point contact diodes for years as well. A galena crystal and a phosphor bronze whisker form a Schottky detector diode.

Making high performance semiconductors requires specialized equipment, environments and processes and is not something you can generally do at home.

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