What is n+ type silicon?

Question

What is n+ type silicon and how is it different than n-type silicon?

Answer 1

n+ is just more heavily doped than n-. Same thing for p type. For example, the source region in an 'n' channel MOSFET is n+, while the drift region is n-, the substrate is n++, the well region is p-, and the well contact region is p+.

A more heavily doped region has lower resistance, but has a lower breakdown voltage. So, n+ has more impurities than n-. n+ could be doped to 10^19 atoms/cm^3, while n- could be 10^13, for example.

You can make silicon n type by adding phosphorus or arsenic. Conversely, you can make silicon p type by adding boron or aluminum. The phosphorus can supply extra electrons to the silicon because it has one more valence electron than silicon. Boron has one less valence electron than silicon, so we call it a hole. Boron can accept an electron.

Answer 2

I am not familiar with the term N+ type silicone. Perhaps it refers to the amount of impurities added to the pure silicone or perhaps you are referring to P type silicone.

Both start out as pure silicone. An impurity is intentionally added to the crystal structure of the pure silicone which determines its electrical characteristics.

An N type silicone is doped with phosphorus which then has an excess of electrons in the crystalline structure. The excess of electrons give this material a negative (hence N) potential.

A P type silicone is doped with boron, which produces an electron deficiency in the crystalline structure. This deficiency of electrons (often referred to as "holes") gives this material a positive potential (hence P type).

That's about it in a nut shell.

Answer 3

I'm guessing that n+ silicon has an excess of 'holes' rather than an excess of electrons in n- silicon. Hence the PN junction formed in the basic diode.