zathris (pixabay user): https://pixabay.com/photos/cpu-chip-semiconductor-condenser-3061923/ Intrinsic to modern electronics, semiconductors are defined as ‘crystalline solids intermediate in electrical conductivity between a conductor and an insulator.’ [1] They have been incorporated in numerous devices including computers, smartphones, bank ATM’s, televisions, washing machines, trains and LED bulbs just to name a few. [2] Band theory Band theory is helpful in visualising the difference between conductors, semiconductors and insulators. Quantum physics dictates that for isolated atoms, the energy states that electrons can occupy are quantised. However, when atoms are brought together to make solids, ‘these discrete energy levels become perturbed through quantum mechanical effects’ [3] As a result, the electrons can occupy a range of energies within a certain energy band. The electrons in an atoms outer shell are situated in an energy band called the valence band. M...