What is a semiconductor diode and how does it work?

Electronics is undoubtedly an extremely extensive area, and among its infinity of components, we have one that is fundamental to electronics, present in almost all electronic equipment or devices, which is the semiconductor diode. Thinking about its importance for electrical as a whole, we will talk about what a semiconductor diode is, what the semiconductor diode is for, what the characteristics of the diode are and how a semiconductor diode works. Come on, guys!

Semiconductor diode: What is it?

Semiconductor diodes are electronic components, which are constructed of semiconductor material, being silicon or germanium. This material allows its conduction capacity to be changed, due to the combination of some factors, such as the addition of impurities in these materials, better known as doping, in addition to the way this component will be fed.

What is a diode and what is the diode for?

Semiconductor diodes are used in apparatus, equipment and electronic devices, such as television, cell phones, computers, stereos, multimeters, chargers, remote controls for television and many others.

It is important to note that there are many different types of diodes, each for its proper application. The most common symbology we find is the rectifier diode, as shown in the image below:

Rectifier diode and its respective symbology.

Semiconductor diode: Types and Applications.

As we already know, semiconductor diodes are present in different types of equipment, devices and electronic devices, each one performs a certain function. The best-known semiconductor diodes are rectifier diodes and light-emitting diodes (LED`S), also known as photodiodes.

The rectifier diode is used to convert signals from alternating current to direct current, maintaining only one semicircle of the sine wave, hence its name “rectifier”. In addition, the rectifier diode can be used normally for any application that requires the passage of current in only one direction or working as protection for the circuit, preventing it from being damaged if fed in the wrong way, for example.

Scheme of operation of a rectifier diode.

The LED light emitting diode is what people generally have a greater knowledge of, as they are present in cell phones, washing machines, televisions, computers, flashlights, remote controls for televisions, lamps, chargers, and others, being used for example to indicate the operating status of a particular device or for lighting.

There are still many other types of diodes, some of which are used as voltage stabilizers, such as the Zener diode for example. In addition, mention other types of diodes, such as the tunnel diode, Gunn diode, Schottky diode, varicap diode, among others.

Semiconductor diode: Operation.

The diode is constructed from semiconductor materials, which are fused to create a junction between a type P crystal and another type N crystal, with the type P crystal representing the positive polarity of the diode, called the anode and the type N crystal representing the negative polarity of the diode called the cathode.

The positive polarity of a diode is where there is a lack of electrons, so this region where there is a lack of electrons is called a gap, however, the negative polarity is where there is the highest concentration of electrons.

When joining the type N and type P crystals, the gaps on the positive side will attract the electrons that are left on the negative side, thus balancing the charges, that is, the charges recombining.

It is important to highlight that this recombination only occurs in the center of this junction, because there the forces of attraction are stronger, in this area the electrons are chemically stable. However, the more distant electrons do not undergo this recombination, due to the lower attraction force, so that this central stability zone is called the depletion layer, or potential barrier.

Internal structure of a diode.

Therefore, we can conclude that the conduction of electric current will depend on the way the diode will be polarized, that is, whether its junction will be polarized in a direct or reverse way. We will show how the diode behaves according to the way it is polarized, the examples below are for the silicon diode, which to start conducting requires a voltage of at least 0.7V, in theory, but which and in practice you can start driving with even less tension.

Reverse bias:

When the diode is reverse polarized the positive pole of the voltage source is connected to the negative side (N) of the PN junction of the diode, this causes the potential barrier to increase, that is, increasing this potential barrier, the resistance of the circuit will be very high, not allowing the passage of electric current. This is because the positive charges of the source attract the negative charges of layer N and vice versa. The image below shows perfectly how this process happens:

Reverse polarized silicon diode.

Direct polarization:

The diode being directly polarized, the positive pole of the voltage source is connected to the positive (P) side of the diode. This makes the positive side become even more positive, and the negative side (N) even more negative, that is, the electrical charges are able to cross the potential barrier between the P side and the N side of the diode, allowing conduction of electric current. This is because the positive charges of the source attract the negative charges of layer N and vice versa.

See in the image below that when the diode is being powered by a voltage lower than 0.7V it does not conduct electrical current, due to its potential barrier, but when the diode is polarized with a sufficient voltage, its potential barrier is broken and the diode starts to conduct electrons.

Directly polarized silicon diode.

The video below complements this article, as we explain how the diode works in practice step by step, in addition to detailing its main characteristics and how the diode behaves.