Semi‐Conductors, Conductors and Insulators — some models for teaching the basic principles

In even the most lucid literature on semi‐conductors, the complexity of electrons, holes, energy levels, acceptors, donors, and so on tends to swamp any understanding of the basic principles. This, we may say, is almost too difficult for us, so it is bound to be too difficult for our students. We then get round the problem by stating categorically that holes exist, that they have the properties of positive charge carriers, and leave it at that to get on to the circuitry.