Quite illustrative with the self-explanatory diagrams. You cannot talk about modern electronics and communication system without mentioning semiconductors especially silicon. Silicon in its purest form is known as intrinsic semiconductors, and it has less conductivity as when you compare it with the one which has some level of an impurity introduced in it, the ones with an impurity atom are said to be doped. Doping is the introduction of impurity atom to increase conductivity. Doping is either done by a trivalent element which has outermost shell electron of three that will enter into covalent bonding with the four outermost electrons of the silicon atom. Since the trivalent electron has one less electron to come into covalent bonding with the four valence electron of silicon, it, therefore, contribute a hole which makes the extrinsic silicon to have majority carrier as the hole and hence is called a P-type semiconductor signifying that the majority carrier is positively charged. The same argument goes when a pentavalent atom is used to dope the silicon atom giving rise to an excess electron which is negatively charged .because the majority carrier is now negatively charged electron, it is therefore called n-type semiconductors.

Other semiconductors include Germanium and Gallium Arsenide. I love semiconductor physics, and I appreciate your work and artistry. Kudos.