P-N JUNCTION

in electronics, the electric contact in transistors and related devices between two different types of material called p-type and n-type semiconductors. These materials are formed by the deliberate addition of impurities to pure semiconductor materials, such as silicon. Materials of p-type contain holes, vacancies formerly occupied by electrons, simulating positively charged particles, whereas n-type materials contain free electrons. Electric current flows more easily across such a junction in one direction than in the other. If the positive pole of a battery is connected to the p-side of the junction, and the negative pole to the n-side, the Fermi levels of the two materials are altered in such a way as to promote the flow of charge across the junction. If the battery is connected in the opposite direction, the Fermi levels are altered in the reverse direction, so that very little charge can flow. This property of the p-n junction is called rectification.