Discussion
A scientist attempts to replace a few carbon atoms in 1.0 g of diamond with boron atoms or nitrogen atoms in separate experiments. Which of the following is correct ?
Answer: B
The correct statement is that with B doping the material will be a p-type semiconductor.
Each carbon in diamond forms four bonds. Boron has only three valence electrons, so a boron atom in a carbon site leaves one bond short of an electron, creating a hole. Holes are mobile positive charge carriers, so boron-doped diamond is a p-type semiconductor (natural blue diamonds owe their colour and conductivity to boron).
Nitrogen, with five valence electrons, donates an extra electron and gives n-type behaviour, so calling N-doped diamond p-type is wrong, as is calling B-doped diamond n-type. Substitutional doping does not require multiple bonds, so the statement that B cannot be incorporated is also false.
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