What are Semiconductors?
Updated: Dec 1, 2020
In an #electric circuit, unlike a resistor, a diode doesn't behave linearly about the applied voltage because it has an exponential I-V relationship. Thus we can't just end by expressing with ohms law which we use for resistors. Diodes are basic unidirectional #semiconductor devices which will only allow current to flow through them in one direction only, acting more sort of a method electrical valve, (Forward Biased Condition).
But, before all this, we doubt semiconductor concept and construction. Diodes are usually made of with Semiconductor material in which features a positive “P-region” at one end and negative N - region at one end. which has the resistivity value in between conductors and semiconductors. But what's a “Semiconductor” material?, How does it work? Let's get into it.
Semiconductors are Germanium and silicon which conducts current but lies in between the conductor and an insulator. They have fewer free electrons because the atoms are placed in a group together with forming a crystal lattice however, electrons can easily able to flow with some special consideration.
The capacity of semiconductors to conduct power can be extraordinarily improved by supplanting or including certain benefactor or acceptor particles to this crystalline-like structure along these lines by delivering more free electrons than openings or the other way around. That is by including a little level of another component to the base material, either silicon or germanium.
On their #Silicon and #Germanium are classed as intrinsic semiconductors, which means pure or undoped conductors. Be that as it may, by controlling the measure of pollutants added to this natural semiconductor material it is conceivable to control its conductivity. Different polluting influences called the acceptors can be added to this natural material to create free electrons or gaps individually.
The process of adding impurities to these silicon and germanium is known as doping. When silicon or germanium is doped with sufficient impurities it no longer remains pure it turns into a p-type semiconductor that has a positive charge. Likewise when silicon or germanium is doped with the specific number of impurities n-type semiconductor is formed which has the most commonly used semiconductor material for a long time is silicon.
Silicon #atom consists of four electrons in its valence shell. In which it shares with its recipient silicon atoms to form one complete orbital with a capacity of eight electrons in the shell. So the structure of these two atoms makes stronger each other. Only there will be few electrons left in silicon atoms that move freely. Crystals are of pure silicon and germanium are insulators or least high value of resistors. Silicon atoms are placed with an equal number of atoms and making them a crystalline strong structure.
The crystal of pure silica (glass) is by and large said to be an inherent crystal (it has no pollutants) and thusly has no free electrons. Be that as it may, essentially interfacing a silicon crystal to a battery gracefully isn't sufficient to extricate an electric flow from it. To do that we have to make a "positive" and a "negative" shaft inside the silicon permitting electrons and hence electric flow to stream out of the silicon. These posts are made by doping the silicon with a specific number of impurities.
1. N-Type Semiconductor
If silicon wants to conduct electricity. It should be impure so that we need to dope it with some impurities like arsenic and antimony or phosphorus into the crystalline structure thus it converts into #extrinsic semiconductor (#impurities added one). The atoms of the elements which are adding to silicon having 5 electrons in the outermost shell so there are specified as pentavalent impurities. These elements allow four out of five electrons to dope silicon.
One electron is freely moving in its shell for mobilizing voltage charge to it. Pentavalent are thus known as donors. Antimony and Phosphorus are extensively used as a pentavalent impurity to silicon. 51 electrons are there in Antimony these are of five shells arranged in atom around its nucleus with the outermost orbital having five number of electrons. Thus the resulting one of basic semiconductor material has an excess of current-carrying electrons, each with a negative charge. Therefore it is known as an N-type material with the resulting electrons known as “Majority Carriers” while the resulting holes are of “Minority Carriers”.
This incitement by an external power source, in which the electrons are freed from the silicon atoms by this stimulation. And quickly will able to replaced by the free electrons which are available from the doped atoms shell. But this will still leave an extra electron which floats around the doped crystal. And makes itself negatively charged. Then the semiconductor material is specified as N-type. Where the donor sensor is greater than the acceptor density. So it has more number of electrons than holes. Because of this one, it is having a negative.charge
2. P-Type Semiconductor
In this one #trivalent impurity is used to dope with silicon. Here for trivalent impurities elements like boron and Indium will come into action. They have only three valence electrons so the fourth closed bound can't be formed in this doping. So it forms holes which have a positive charge. Holes are places where electrons are missing in an atom. So now a hole in the silicon crystal which a neighbouring electron is attracted to it and it tries to move into the hole to fill it.
However, if it is filled it remains another hole behind it as it moves. This, in turn, attracts another electron which in turn creates another hole behind it, and so forth thus the holes are with the positive charge through the crystal structure. Each of the impurity atoms generates a hole so the trivalent impurities are generally specified as “Acceptors” which continually accepts the electrons. Boron is the most additively used trivalent impurity as it has only five electrons in its atom which are placed in three shells around its nucleus with the outermost one having only three electrons.
The doping of Boron atoms causes conduction and forms positive charge carriers which resulting forms the P-type material with the positive holes so eventually they are known as “Majority Carriers”. And remaining free electrons are known as Minority charge carriers. So the semiconductor basics material is classed as P-type. This density of acceptor is more than that of the donor. Therefore in result P-type holding more holes.
Semiconductors are mainly used in the production of diodes, electronic devices, transistors. Also, semiconductors are applied to compactness, reliability, power efficiency, and low cost.