What happens when we run out of it?
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Silicon is widely available and is the second most common material at 27.7% by mass in the earths crust, as a result it’s dirt cheap and perfect for most semiconductor applications.
There are many other semiconductors that can be used, germanium, silicon carbide, tin oxide, aluminium nitride among others and some of them have better performance than silicon in certain applications (germanium makes better solar panels than silicon).
But the deciding factor is cost, silicon is adequate for most applications that do not require specific properties so it is most widely used. If you require a minimum performance limit for an application and cost is not really an issue (such as solar panels for the ISS) then you would use the best material for the job, but for household solar panels silicon works well enough.
There are even materials called compound semiconductors which are essentially custom made materials for an application, but these are crazy expensive to make and can only be made in small quantities.
TLDR: Silicon is cheap as hell and adequate for most applications, including high end computer chips
Silicon reacts kind of funny when combined with small amounts of other chemicals and then powered with electricity; with some arrangements it allows the electricity to flow, and with other arrangements it stops the electricity. Sort of like an electrical switch, but one that doesn’t need to move. We call these electronics ‘transistors’.
Before silicon transistors, one of the things used was vacuum tubes. They were huge, produced much more heat, and were a fraction of the speed of silicon ones. There’s a reason there’s advertisements from decades ago talking about how 1 kilobyte is more memory than any human could possibly use, but nowadays we use 1000’s more than that even looking at a static web page; transistors are literally thousands or millions of times better than the tubes were.
The simplified way we’ve designed computers (arguably since the abacus) is “do an action if the data is a certain way”. With transistors and binary, we can do this billions of times every second. Replacing silicon transistors with any thing else requires either physical movement or an element that responds to electricity in a similar way to silicon without being too expensive.
A quarter of Earth’s crust is silicon. Most sand is mainly silicon dioxide, i.e. silicon that reacted with oxygen. We will never run out of it. We might run out of the most easily accessible resources for extremely pure silicon, increasing the price for it a bit.
Computers are basically a giant array of switches controlling other switches. Each switch (transistor) can be turned on (conduct electricity) or off (block it). You cannot use materials that are always conducting for that, and you cannot use materials that are never conducting. Silicon is a semiconductor: As pure element it conducts relatively poorly and its properties can be influenced easily by adding some other elements to it. That’s a relatively rare property. The closest replacement would be germanium but that is far less common, and switching the whole industry from silicon to germanium would be extremely expensive. There are also some combinations of different elements that work, like silicon+carbon and gallium+arsenide. We use these in some specialized applications.
Silicon is a semiconductor, in certain conditions it conducts, and in others, it doesn’t. Germanium is really the only other contender for how we use silicon, and thats much rarer. We don’t really have a risk of a shortage, though, as it’s the second most common element in the Earth’s crust, making up over a quarter of it (second only to oxygen).
There is an ongoing shortage of silicon wafers in the semiconductor industry, but that’s more of a production issue than a supply of silicon.
The computer chip shortage is in part a result of the wafer shortage, and also the fact that the process to turn a wafer into chips takes thousands of hours of work.
Silicon is, in orders of most importancy: (1) semiconductor that we can prepare with extremely purity, (2) It’s bandgap is large enough to operate at room temperature. (3) it is easy to dope for p and for n over a large range. (4) the raw material is abundant.
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