I read that the doping ratio is usually around 1 impurity/10 million atoms. Why is that ratio so low? Can’t the semiconductor conduct electricity better if there were more charge carriers?
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2\$\begingroup\$ Here's a frame challenge for you: Why is conducting electricity better an advantage? Are you sure you always want it to conduct better? \$\endgroup\$– HearthCommented Jul 10, 2022 at 20:25
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\$\begingroup\$ or, to be even more explicit than Hearth: Think about why we dope semiconductors at all, instead of just using plain old copper, which conducts a hell of a lot better. \$\endgroup\$– Marcus MüllerCommented Jul 10, 2022 at 21:41
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\$\begingroup\$ Because that's all you need :) Terrible things happen when you over-dope. For example, the way to make low-voltage Zener diodes (less than 20V, say) is to heavily-dope them. Lots of doping lowers the breakdown voltage, something we usually want to avoid. Lots of doping makes semi's much worse with changes in temperature. Lots of doping increases capacitances, increases stored-charges (i.e. making "turn-on/turn-off" slower). And besides, 1 in 10MM is enough to conduct more than enough amperes to get most work done. I agree, though, it does seem weird that it works at "only" 1 in 10MM! \$\endgroup\$– AtomiqueCommented Jul 12, 2022 at 19:10
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