By now you may be getting bored with me and my cup. But I am going to use it for just one last example to explain n and p doping with an approach that differs slightly from the one Sally just gave you.

In a pure semiconductor at low temperature, the valence layer is completely filled with electrons and the conduction band is empty. That would be equal to one filled and one empty compartment in my cup. The water (electrons) can't move because there is no empty space.

The p in p-doping stands for positive. This is because compared to the atoms in the semiconductor material the added atoms have fewer negative valence electrons. In the p-doped semiconductor the higher conduction band is empty, but there will be holes in the valence band.

In the cup, this means that we remove some water from the valence compartment. In other words, we form air bubbles (positive holes) in the water. Now if we tip the cup, there is room for the water (electrons) to move in one direction and for the created holes (lack of electrons) to move in the opposite direction (just like bubbles would do in water).

The n in n-doping stands for negative. This is because compared to the atoms in the semiconductor material the added atoms have more negative valence electrons. In the n-doped semiconductor, the valence band is full so there is no room for the electrons to move there. Instead, the extra electrons move into the conduction band.

In our cup, we can see that no water will move in the full valence compartment. Instead, the extra water (electrons) added will move within the conduction compartment.