what property of the materials used in computer chips makes them useful as switches that trun electricty on and off
nothing
The property of materials used in computer chips that allows them to function as switches and control the flow of electricity is known as "semiconductor behavior." Specifically, semiconductors are materials that can conduct electricity under certain conditions and act as insulators under other conditions.
In computer chips, the most commonly used semiconductor material is silicon. Silicon has four valence electrons in its outermost shell, which allows it to form a crystal lattice structure. This structure is crucial for its semiconductor properties. By adding certain impurities, known as dopants, to the silicon crystal, we can control its electrical behavior.
Two commonly used dopants are phosphorus (with one more valence electron than silicon) and boron (with one fewer valence electron than silicon). When phosphorus is added to silicon, it creates an excess of electrons, resulting in an n-type semiconductor - where "n" refers to the majority charge carriers being negative electrons. On the other hand, when boron is added, it creates a deficiency of electrons, resulting in a p-type semiconductor - "p" indicating the majority charge carriers being positive holes.
The interface between the n-type and p-type semiconductors forms what's called a junction, specifically a pn junction. This junction behaves as a switch, enabling the control of the electrical current flow. When a voltage is applied across the junction in the forward bias mode (positive potential on the p-side and negative potential on the n-side), the excess electrons from the n-side and holes from the p-side flow towards each other, leading to a conductive state. This allows electrical current to flow through the junction.
Conversely, when a voltage is applied in the reverse bias mode, the electrons from the n-side are attracted towards the positive potential of the p-side, while the holes from the p-side are attracted towards the negative potential of the n-side. This creates a depletion region, where no current flows, and the junction acts as an insulator or a switch that is turned off.
By combining multiple pn junctions and controlling their electrical states using intricate patterns of doping and connections, we create the fundamental building blocks of computer chips - transistors. These transistors can be arranged in complex circuits to perform a wide range of functions, such as switching and amplifying electrical signals, enabling the functionality of modern computers.