Semiconductors are the middle phase of the conductor and insulator. Semi is showing half & conductor indicates conductivity. Hence half conductivity. We have classified all the materials into three categories conductor, semiconductor, and insulator. The semiconductor’s conductivity lies between the conductor and insulator. All the diodes and transistors are made from these semiconductors.
What is a Conductor?
They conduct electricity very easily. They have very low resistivity because of so many free electrons. The charge can flow very easily from them. For example, copper, iron, and silver.
What is an Insulator?
These are highly resistive substances. They have very lesser free-electron and even tends to have no free electron. Resulting in they can not conducting electricity. For example, diamond.
What is a Semiconductor?
Semiconductors have intermediate resistivity between them. They cannot conduct electricity as efficiently as a conductor does. And also, not provide a hindrance like an insulator. They have few electrons which help in conductivity. Like Silicon, Germanium, etc.
In the US there are lots of Silicon-related computer hardware and software companies. That is why that place is famous with the name Silicon Valley.
Nowadays this is very easy to share information. We don’t need to be very close o another person to talk to them. If we are far away then also easily we can talk to each other. Even we can see them also. Why did this revolution come? Who has to make it? Definitely, it is because of the internet. But there is an important role of the device also. We have seen that when these devices just started on the market they are very much costlier than now. The device which we are using to make these devices are the backbone of it.
In the nineties, computers were there but that was very much costlier than now. With invention and technical development, things are getting cheaper and cheaper. And now we all can afford that. Logic Gates. We have created several logic gates. This was very compact and cheaper. The electronic diode and transistor was the main fundamental of it.
Why we use semiconductors in devices
Generally, we use semiconductor devices where we need control currents like amplifiers in microphones, high, and processors.
Energy bands in Solids
Energy bands dictate the energy levels of electrons present inside the atoms of solids. Because of the quantum physics principle called Pauli’s exclusion principle. It states that no two electrons have the same quantum energy state. In simple words, no two-electron have the same energy as a result all electrons shell combined will have different energies.
Which makes the arrangement of energy that is called the band. The outermost shell of an atom is known as the valance band. They represent the energy of valence electrons.
Types of Semicondutor
On the behalf of the composition and structure of semiconductors, they are classified into two parts. Intrinsic and extrinsic semiconductors.
Holes and free electron
Let’s take an example we have taken a tetravalent crystal structure. Tetravalent has four electrons in its valence shell. Mena in its outermost shell there are four electrons present. For stability, we know an atom needs to complete its octet. For that purpose, this atom forms a covalent bond with its four neighboring atoms. But when this atom gets heated.
That energy force this electron to leave its valance band and this transfer to the conduction band. When this electron leaves the place. There is an empty space is created that empty space is called a hole. These free electrons and holes are combinedly called charge carriers. These holes are acting as a positive charge, They trap that free electron from another atom. Again, in that second atom, a second hole was created. This is how these semiconductors work.
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These are the purest form of semiconductor. This has low conductivity from extrusive semiconductors. The above explanation for holes and free-electron is an example of the working of these types of semiconductors.
Intrinsic types of semiconductors have low conductivity. To improve that we add some impurities to them which is not affecting the chemical composition but increases the conductivity. Hence, the formation of extrinsic semiconductors forms.
These are impure semiconductors made from the mixing of other elements in semiconductors. This improves conductivity.
What is Doping?
The process of adding impurity to a pure tetravalent substance is known as doping. Through doping, the conductivity of the semiconductor gets increases. With the increasing number of free- electrons. Doping elements are the adjacent elements of group 13 and group 15.
There are further two types- n-type semiconductor and p-type semiconductor.
When there is the addition of a pentavalent atom to the semiconductor. Here n stands for a negative charge. Because there are five electrons in its outermost shell always a single atom always free for conductivity. That will be responsible for the conductivity of the current.
When there is the addition of trivalent impurity to the semiconductor. Here, p stands for positive. Naturally, a hole is created because that atom has only three electrons in its outermost shell.
In both the above examples there is a natural creation of charge carriers without the addition of heat. Hence, they can conduct more electricity than intrinsic semiconductors at room temperature. The ratio we use to add this impurity is 1:106
Now current can move In any direction. That will either waste energy or maybe the resulting current can be zero. That is why we made a p-n junction diode. This name simply tells that this diode is made from p and n-type semiconductors.
Important: Point that must be noted is that We are not mixing tetravalent and pentavalent atoms at a particular time. First, we need to make p-type semiconductors and n-type semiconductors. Then only we will add them.
Working on P-n junction
When we will join p and n-type semiconductors. There are so many vacant holes acting like positive charges in p-type semiconductors. And there are free electrons in n-type semiconductors. So, the natural negative charge starts to move towards that holes. Hence charges started to move in a fixed direction naturally. But the question is. Is it again get homogeneous? Actually, not because when this diffusion takes place there is depletion of negative charge and positive charge. P-type semiconductors contain a negative charge and n-type contains a positive charge. This depleted charge started to penetrate that natural transfer of electrons and holes. Due to the same charge repletion.
Current can travel from the n-type region to the p-type region through these free electrons.
The current produces between the depletion layer.
At a particular time diffusion curet become equal to drift current in this phase, that is the equilibrium state. This p-n junction allows the current to move in a particular direction but also provided hindrance in another direction. The reason for this is forward biasing and reverse biasing
When holes and free-electron start to move hence different charges occur. Because initially, the overall atom was neutral. Then in the middle of the p and n-type region, there is the creation of the depletion region. That creates a potential that is barrier potential.
We can connect our p-n junction with the battery in two ways on that there are further two types of it.
Connecting p-n junction of semiconductors
When we connected the p side to the negative terminal of the battery means we connected the negative to the positive. This biasing is forward biasing. Actually, this will attract that negative layer.
In this biasing p-type region will connect to the positive terminal of the cell. Although, there is great repletion. This biasing is revere biasing.
Where do we use semiconductors?
The development of semiconductor devices, which are necessary for a wide range of electronic products, is the primary use of semiconductors. Semiconductor devices are the replacement for vacuum tubes in practically all applications because they conduct electric currents in the solid state rather than as free electrons across a vacuum.
The diode functions as a one-way valve in a circuit. This only permits the flow of current in one direction. One of the most widely used semiconductor components. On the other hand, conductors permit bidirectional current flow.
Transistors, use in both quick switching and current amplification. Also designed with semiconductors.
list of things where we use semiconductors
Applications of Semiconductors give a boost to the technology industry. They are easy to use, lightweight, and have great efficiency to work. Which makes it this much technology-friendly usage. Here are some important devices in which we can see semiconductors.
The most popular semiconductor device in use today is the MOSFET (metal-oxide-semiconductor field-effect transistor).
Semiconductor components like integrated chips, diodes, and transistors use to power devices like mobile phones, computers, game consoles, microwaves, and refrigerators. The reason there are currently such significant wait times for many consumer electrical items is in part due to the enormous demand for these products.
Embedded systems are little computers that are integrated into bigger machines. They enable user engagement and have control over the device. Central heating systems, digital watches, GPS systems, fitness trackers, televisions, and engine management systems in automobiles are just a few examples of embedded systems that we frequently utilize.
Because some semiconductors have high thermal conductivity, they can be employed in some thermoelectric applications as a cooling agent.
Lighting and LED displays
Some semiconductors can create light and are utilized in LEDs and OLEDs. Typically, these semiconductors are liquid or amorphous and are available as thin-coated films.
Solar cells made from semiconductors
Silicon is also the semiconductor that is most frequently utilized in the manufacture of solar panel cells.
In addition to consumer devices, semiconductors are essential to the operation of trains, Bank ATMs, The internet, and Communications Other facets of the social infrastructure, including, among other, things, medical networks utilized for aged care.
These Semiconductors have created a drastic change in the market. That resulted in new technology products. Internet one of the basic need of today is also possible with these semiconductors. The devices which we are using are one in our cell phones that are present. The main region for these cheaper devices is what we are using today.