P-Type and N-Type Semiconductors

Q1: What's an application of doping?
A1: You can use doping to make p-type and n-type semiconductors.

Q2: What semiconductor can I use to make these p-type and n-type semiconductors?
A2: You could use silicon, a Group IV element. A silicon atom has 4 valence electrons, which may be paired up with another 4 electrons from 4 neighboring silicon atoms through 4 covalent bonds (for the sake of stability). At room temperature, not all of the electrons are held in covalent bonds in pure silicon. Some of these electrons can move around.

Q3: What's the difference between p-type and n-type semiconductors?
A3: The difference lies in the parity of their charge carriers, charged particles that are free to move around. P-type semiconductors have positive charge carriers while n-type semiconductors have negative charge carriers.

Q4: How can I dope silicon to make a p-type semiconductor?
A4: You can introduce boron, a Group III element, as an impurity. Neighboring silicon atoms see boron's lack of a fourth valence electron as a hole. For stability, boron may take the electron of a nearby silicon atom. Hence, boron is referred to as an acceptor atom. After accepting the electron, the boron atom becomes a negative ion and the hole is relocated from boron to a silicon atom. In turn, this silicon atom may fill its hole with an electron from another silicon atom. And so on. The takeaway is that this hole moves freely and serves as an positive charge carrier.

Q5: How can I dope silicon to make n-type semiconductors?
A5: You can introduce phosphorus, a Group V element, as an impurity. Neighboring silicon atoms see phosphorus's fifth electron as excessive. For stability, phosphorus may give its extra electron to a nearby silicon atom. Hence, phosphorus is referred to as a donor atom. After donating its electron, phosphorus becomes a positive ion and the extra electron is relocated from phosphorus to a silicon atom. In turn, this silicon atom may rid itself of the extra electron by donating it to another silicon atom. And so on. The takeaway is that this extra electron moves freely and serves as a negative charge carrier.