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Author Topic: n-type vs p-type  (Read 2610 times)

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BluePill

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n-type vs p-type
« on: September 09, 2011, 08:49:29 PM »

I am confused with the idea of n-type and p-type semiconductors.

If you dope Si with P, it becomes an n-type while Si with Al becomes a p-type. What I don't get is that ZnO thin films would become n-type if doped with Al3+. Wouldn't that make it p-type? Moreover, why is Cu+ less effective in transforming it to n-type?

Much I've read has been telling me that n-type are electron conducting and p-type are hole conducting. This doesn't make sense.
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Enthalpy

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Re: n-type vs p-type
« Reply #1 on: October 14, 2011, 01:14:28 PM »

I too learnt that story or Al and P in silicon, with electron and holes conduction, and didn't feel it so senseless. At least, it could explain much of what I experimented. And since this very theory is applied with success to produce chips, there must be some truth in it.

I haven't studied ZnO, but if comparing with GaAs, I suppose the effect of a dopant depends on what atom it replaces... Al replacing Zn would bring one more electron, making it N-type. Within the crystal, Al would become Al3+, replacing Zn2+. And if Cu has a valence of 2, it won't dope anything by replacing Zn. As well, a dopant level must be near enough to the conduction or the valence band, or it will  be a recombination centre instead of a dopant.

A dopant tends to replace the bigger ion in the crystal, which must be Zn2+ rather than O2-. But in a thin film, which uses to be polycrystalline or amorphous, these simple reasons that work for single-crystals can be very wrong, as grain joints determine most properties and suck impurities.
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