Semi-Conductor Diodes Essay

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Semiconductor Diodes

A diode is considered the simplest possible semiconductor device, but it is also very useful. You find semiconductors at the heart of microprocessor chips as well as transistors. Anything that's computerized or uses radio waves depends on semiconductors.

How Semiconductor Diodes work

Semiconductor diodes are usually made of doped silicon or in some circumstances germanium. Pure silicon is referred to as almost an insulator, very little electricity will flow through it. This is why silicon is 'doped' to change its properties. To dope silicon you need to mix it with impurities, there are two types of this doping.

The first type is the 'N-type'. In this type of doping arsenic or phosphorus is added to the silicon. These elements are used as they have five outer electrons. Silicon has four outer electrons, which allow them to bond with these elements and for there to be a spare electron for arsenic/phosphorus. These leaves the electrons with no purpose but to roam around the atoms and with enough of the impurity it does not take long for an electric current to form with all of the free electrons. All of these electrons will have a negative charge, hence the name ‘N-type’.

The second type is the ‘P-type’. This process uses gallium or boron as the dopant. These elements have three outer electrons and when mixed with the silicon lattice, forms holes in the lattice where a silicon electron has nothing to do. The lack of an electron in the dopant creates a positive charge, giving it the name of ‘P-type’. These holes can conduct current by the process of accepting an electron from another source. Although doping silicon crystals with these techniques will not turn a good insulator into a great conductor, it will still transform it into a sustainable conductor, hence the name ‘semi-conductor’.

Although P-type and N-type silicon is conductive, when placed into a circuit (shown on opposite side) no current will flow across this junction as the negative extra electrons are attracted to the positive terminal, and the positive holes are attracted to the negative terminal of the battery. But, when the battery is switched around the negative electrons will be repelled by the negative terminal and the positive holes will be repelled by the positive terminal. This results in the two meeting at the central and reacting with each other. This makes the negative electrons react with the positive holes and for the electrons to fill the places of the holes. This allows current to flow and the circuit to be complete.

Purpose of a Semiconductor Diode

A diode is a device which is used in a circuit that blocks the current for one direction, therefore letting the current flow in the opposite direction. There are various uses for Diodes. A diode can be critical in a circuit which involves batteries.
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