Semiconductor

Semiconductors are substances that can gain conductive properties under the influence of mechanical regulations and are insulating under normal conditions.

If resistors are the most basic passive component in electrical or electronic circuits, then we can consider Signal Diode as the most basic active ingredient.

However, unlike a resistance, a diode does not act linearly according to the voltage applied because it has an exponential IV relationship, and therefore cannot be simply defined using the Ohm law, as we do for resistors.

Diodes are basic one-way semiconductor devices that act more like a one-way electric valve (Advanced State), allowing the current to flow through them in only one direction.However, before looking at how signal or power diodes work, we need to understand the basic structure and concept of semiconductors.

Diodes are made of one piece of semiconductor material with a positive "P-zone" at one end and a negative "N-zone" at the other end, and an extractor value between a conductor and an insulator.However, before we get into the topic of "Semiconductor" material, we need to examine conductive and insulating substances.

Reminder

In many sources and internet articles, you can see that silicon is written instead of silicon. This is a complete translation error. The "Silicon" element used in English is mentioned as silicon in many sources due to an incorrect translation, but the Turkish equivalent of this element is "Silicon". If we give an example of this, the location we know as "Silicon Valley" is actually "Silicon Valley"with an accurate translation. Once you understand the semiconductors and silicon connection, you can realize how meaningful the name given to this location is.

What is Self-Esteem?

Resisting the electric current of an electrical or electronic component or device is called an resistive. Based on the principles of the Ohm Act, it is defined as the ratio of the voltage difference on it to the current passing through it.The main problem of using resistance as a measurement is that it depends very much on the physical size of the material being measured and the material in which it is made.For example, if we increase the length of the material (by making it longer), its resistance will also increase proportionally.

In the same way, if we increase its diameter or size (thickening) the resistance value will decrease.Therefore, being able to identify the material in such a way that it shows the ability to transmit or resist the flow of electric current through it, regardless of size or shape, will make our job quite easy in calculations.

The quantity used to indicate this particular resistance is called an resistive, and the Greek symbol ε , ( Rho ) is given.The extract is measured in Ohm-meters, (Ω.m).Self-esteem is the opposite of conductivity.

When the extractors of various materials are compared, they can be divided into three main groups: Conductors, Insulators and Semiconductors, as shown below.

semiconductor

Conductors

Due to the graph above, we know that conductors arematerials with very low self-esteem values, usually in micro-ohms per meter.This low value allows them to easily pass an electric current, since there are plenty of free electrons floating within basic atomic structures.But these electrons will only flow through a conductor if there is something that will stimulate their movement and it is something electrical voltage.

When a positive voltage potential is applied to the material, these "free electrons" leave their main atoms and move together through the material, which creates an electron shift, more commonly known as current.How "freely" these electrons can move within a conductor depends on how easily they can break away from the atoms that make them up when a voltage is applied.Then the amount of electrons flowing depends on the amount of resistance that the conductor has.

Good conductive samples are usually metals such as Copper, Aluminum, Silver or non-metal materials such as Carbon, since there are very few electrons in the outer "Valans Shell" or ring of these materials, which cause them to be easily ejected from the orbit of the atom.

semiconductor

This allows them to flow freely through the material until they merge with other atoms, producing a "Domino Effect" throughout the material, thereby creating an electric current.Copper and Aluminum is the main conductor used in electrical cables as shown.

Generally speaking, most metals are good electrical conductors, as they usually have very small resistance values in the micro-ohm/meter (μΩ.m) zone.

Metals such as copper and aluminum transmit electricity very well, but they still have some resistance to electron flow and, as a result, do not transmit perfectly.

Energy lost during the passage of electric current occurs in the form of heat, so conductors and especially resistors heat up as the ambient temperature and resistance of conductors increases.

Insulators

Insulators are the opposite of conductors.Electrons in the outer precious shell are made of materials that are usually non-metal, with little or no "free electrons" floating within their basic atomic structures, as they are strongly drawn by the positively charged inner core.

In other words, electrons stick to the main athe and cannot move freely, so if a potential voltage is applied to the material, no current flows, since there are no "free electrons" that can move, which provides insulation to these materials.

Insulators also have very high resistances, millions of ohms per meter, and are usually not affected by normal temperature changes (although at very high temperatures they become charcoal and turn from an insulator into a conductor).Examples of good insulators include marble, molten quartz, PVC plastics, rubber, etc.

Insulators play a very important role in electrical and electronic circuits because without them, electrical circuits short-circuit and do not work.For example, insulators made of glass or porcelain are used to insulate and support overhead transmission cables, while epoxy-glass resin materials are used to make printed circuit boards, PCBs, etc., as shown to insulate PVC electrical cables.

Semiconductors

Semiconductor materials such as silicon (Si), germanyum (Ge) and gallium arsenide (GaAs) have electrical properties somewhere in the middle, between "conductive" and "insulating". They are not good conductors or good insulators (hence they are called "semi" conductors). They have very few "free electrons" because their atoms are grouped closely together in a crystalline model called the "crystal lattice", under special conditions their electrons can flow.

The ability of semiconductors to transmit electricity can be greatly improved by the addition or replacement of certain donor or receiving atoms to this crystal structure, so that more free electrons can be produced through holes, or vice versa. This is accomplished by adding a small percentage of another element, such as silicon or germanyum, to the basic material.

In their own right, silicon and germanium are classified as intrinsic semiconductors, that is, they are chemically pure and contain nothing but semiconductor material. However, it is possible to control its conductivity by controlling the amount of impurities added to this intrinsic semiconductor material. Various impurities called transmitters or receivers can be added to this intrinsic material to produce free electrons or holes, respectively.

The process of adding donor or receiving atoms to semiconductor atoms (1 rank of impurities atoms per 10 million (or more) atoms of the semiconductor is called Doping. Since additive silicon is no longer pure, these donor and receiving atoms are collectively called "impurities", and by adding a sufficient number of impurities to this silicon material, we can convert it to type N or type P.

By far the most widely used semiconductor basic material is silicon. In the outer exopliation of silicon, there are four precious electrons that it shares with neighboring silicon atoms to create a full orbit of eight electrons. The structure of the bond between the two silicon atoms is such that each atom shares an electron with its neighbor, making the bond very stable.

Since there are very few free electrons that can move around the silicon crystal, pure silicon (or germanum) crystals are therefore good insulators, or at least very high-value resistors.

Silicon atoms are arranged in a certain symmetrical order, which makes them a crystalline solid structure. It is often said that a pure silica crystal (silicon dioxide or glass) is an intrinsic crystal (it does not have impurities) and therefore does not have free electrons.

But connecting a silicon crystal to a power source is not enough to extract an electric current from it. To do this, we need to create a "positive" and a "negative" pole in silicon that allows electrons and therefore electric current to flow through the silicon. These poles are formed by the addition of silicon with certain impurities.

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Silicon Atomic Structure

The image above shows the structure and lattice of a 'normal' pure silicon crystal.

N-type Semiconductors

In order for our silicon crystal to transmit electricity, we need to introduce an impurity atom such as Arsenic, Antimony or Phosphorus into the crystal structure and externalize it (impurities are added). These atoms have five outer electrons to share with neighboring atoms in their outerest orbits, often referred to as "Five-valued" impurities.

This allows four of the five orbital electrons to be connected by neighboring silicon atoms, and when an electric voltage is applied (electron flow), it activates a "free electron". Since each impurity atom "donates" an electron, five-valued atoms are often known as "transmitters".

Antimony (symbol Sb), as well as Phosphorus (symbol P), is often used as five valuable additives to silicon. Antimony has 51 electrons arranged in five shells around its nucleus, with five electrons in the outermost orbit. The resulting semiconductor basic material has overcurrent electrons, each with a negative charge, and therefore its electrons are called N-type material called "Majority Carriers/Majority Carriers", while the resulting holes are called "Minority Carriers/Minority Carriers".

When stimulated by an external power source, electrons released from silicon atoms are quickly replaced with free electrons that can be obtained from additive Antimony atoms. However, this movement still leaves an extra electron floating around the additive crystal, making it negatively charged.

A semiconductor material is then classified as an N-type when the donor density is larger than the receiver density, that is, when it has more electrons than the holes and thus forms a negative pole, as shown.

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Antimony Atomic Structure

The image above shows the structure and cage of the donor/donor impure Antimony atom.

P-type Semiconductors

If we go the other way and add a "Trivalence" (3-electron) impurity to the crystal structure such as Aluminum, Boron or Indium, which have only three precious electrons in their outerest orbits, there can be no fourth closed bond.Therefore, a complete connection to the semiconductor material is not possible, giving it an abundance of positively charged carriers, known as holes in the structure of the crystal, where electrons are effectively missing.

Now that there is a hole in the silicon crystal, a neighboring electron is drawn to it and tries to enter the hole to fill it.But the electron that fills the hole leaves another hole behind as it moves.This, in turn, attracts another electron that forms another hole behind it, giving the appearance that the holes act as a positive load along the crystal structure (traditional current flow).

This movement of the holes causes a lack of electrons in the silicon and converts the entire additive crystal into a positive pole.Since each impurity atom forms a hole, trivalence impurities are often known as " Receiver " because they consistently "accept" excess or free electrons.

Boron (symbol B) is widely used as a trivalent additive, as it has only five electrons arranged in three shells around its core and only three electrons in the outermost orbit.Doping of boron atoms causes transmission to consist mainly of positive load carriers, and positive holes are obtained from a P-type material called "Majority Carriers" and free electrons called "Minority Carriers".

Then a semiconductor basic material is classified as p-type when the receiver density is greater than the donor density.Therefore, a type P has more holes than semiconductor electrons.

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Boron Atom Structure

The image above shows the structure and cage of the boron atom, the receiving impure.

Summarize

N-type (e.g. Antimony additive)

These are materials that have been added pentavalent impurity atoms (Donors) and transmitted by the movement of "electrons", and are therefore called N-type Semiconductors.

Type N semiconductors have:

  • 1. Donors are positively loaded.
  • 2. There are a lot of free electrons.
  • 3. A small number of holes based on the number of free electrons.
  • 4. Doping provides:
    • positively charged donors.
    • negatively charged free electrons.
  • 5. The energy supply provides:
    • negatively charged free electrons.
    • positively charged holes

Type P (e.g. Boron additive)

These are materials that are added Trivalent impurities (Asceptors) and move with the movement of "holes", and are therefore called P-type Semiconductors.

In such materials:

  • 1. Acceptors are negatively charged.
  • 2. There are a lot of holes.
  • 3. A small number of free electrons based on the number of holes.
  • 4. Doping provides:
    • negatively charged receivers.
    • positively charged holes
  • 5. The energy supply provides:
    • positively charged holes
    • negatively charged free electrons.

and both P and N-types are electrically neutral on their own as a whole.

Antimony (Sb) and Bor (B) are two of the most widely used doping agents because they are more easily accessible than other types of materials.They are also classified as "metaloids".However, the periodic table combines a series of other different chemical elements with three or five electrons in the outermost orbital shell, making them suitable as a doping material.

These other chemical elements can also be used as additives to Silicon (Si) or Germanyum (Ge) foundation material to produce different types of basic semiconductor materials for use in electronic semiconductor components, microprocessor and solar cell applications.These additional semiconductor materials are given below.

Periodic Table of Semiconductors

Element Group 13Element Group 14Element Group 15
3 Electrons in The Outer Layer
(Positively Charged)
4 Electrons in The Outer Layer
(Neutral Loaded)
5 Electrons in The Outer Layer
(Negatively Charged)
(5) Boron (B)(6) Carbon (C)
(13) Aluminum (Al)(14) Silicon (Si)(15) Phosphorus ( P )
(31) Gallium (Ga)(32) Germanyum ( Ge )(33) Arsenic ( Ace )
(51) Antimony ( Sb )

In the next content related to semiconductors and diodes, we will look at combining two semiconductor basic materials, P-type and N-type materials, to create a PN Connection that can be used to produce diodes.