Understanding Electronics: What is a Semi-Conductor?

Semiconductors are primarily used in electronic circuits, it is a material that conducts current, but not in its entirety. They are mostly made out of crystals of certain materials, silicon is the most common. In terms of its conductivity, it has a similar range with that of an insulator, which has almost no conductivity.

How does it work?

Understanding how semiconductors work also means understanding first the basics of how electrons are organized in an atom. There are hundreds of electrons in an atom, and they are organized in different layers. These layers are called shells with the outermost categorized as the valence shell. These electron plays an important role in the shell because they are the ones that form bonds with nearby atoms.

When that happens, the bonds are now called covalent bonds. This is relevant in a semiconductor because it typically has four electrons in its valence shell. A number that differs from a conductor. When the valence electrons bind with other valence electrons from other atoms, the atoms arrange themselves into structures called crystals.

When other elements are introduced deliberately into a crystal, the process is now called doping and the elements introduced to the crystal is called dopant. When this process happens, silicon crystals now transforms into one of two distinct types of conductors.

Types of conductors

N-type semiconductor: This type of conductor is created when the dopant element is consists of five electrons in its valence layer. Phosphorus is very common in this process, its atoms join right in the crystal structure of the silicon, each forming one bond with four adjacent silicon atoms. Phosphorus atoms normally have five electrons in its valence shells, but only four of them are bonded to adjacent atoms, leaving the other atom left with nothing to do.

P-type semiconductor: The semiconductor is called a P-type when the dopant has only three electrons in the valence shell. A normal process of a semiconductor involves a small amount being incorporated into the crystal, when that happens the atom can bond with four silicon atoms present in the semiconductor. However, since a P-type has only three electrons to offer, a hole is now created which behaves like a positive charge.

Regardless if it is an N-type or a P-type semiconductor, when a voltage is applied to either of them, current technically flows for the same reason that it flows in a regular conductor. Despite the lack of electrons is a P-type semiconductor it still results in an organized process moving in one direction thereby creating a measurable electric current.

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