The Beginning
There are 850 crore transistors in any phone. In the same way, a computer has about a few crores of transistors. Transistors are used in all types of electronic devices in the world today. What is this widely used transistor for us today and how does it work.
The basic principals of transistors are very simple. It only acts as a switch that controls the flow of electricity. One when there is current flow and zero when there is no current flow. These zeros and ones run all kinds of devices today. In addition, the information that is currently there is also stored and processed in this way. For example, the files saved on the memory card, watching videos on YouTube, exchanging messages. As in a simple switch, there is a moving part in the down position, it is on and in the up position, it is off. In case of transistor, however, there is no such moving part. As a result there is no need to control through people. All this has been made possible by replacing semiconductors.
What is Transistor and Semiconductor(n-type and p-type)?
Materials that behave as conductors or insulators but behave as both are called semiconductors. Such as pure silicon. However, heat has a considerable effect on semiconductors. Since silicon has four electrons in its last energy level, silicon is covalently bonded to four silicon atoms around it. In this condition, when low voltage electricity flows, it behaves like a conductor. If high voltage electricity flows again, it again acts as a conductor.
Doping of Semiconductors
Conductivity of semiconductor can be increased by doping. Elements that have five electrons in the last orbital, such as phosphorus mixed with a small amount of silicon, are called n-type semiconductors. In this case, the number five electron of phosphorus is not under any atom. As a result it can move freely. As a result, the electrical conductivity of silicon increases. On the other hand, those elements that have three electrons in the last orbit, such as boron mixed with a small amount of silicon, are called p-type semiconductors. In this case, the three electrons in the last orbital of boron form a bond with the four electrons of silicon. But boron has a vacancy called a hole. But in this case also the electrical conductivity increases. Because another electron comes in to fill that hole. This results in the creation of holes in another place. This is basically how electricity is transported. In this way electricity flows mainly as a result of the transfer of holes here.
Now where the hole is formed there is a shortage of electrons that means it is positive that is why it is called p-type. On the other hand, N-type has an extra electron ie indicates negative. That does not mean that p-type is positively charged and n-type is negatively charged. All these n-type and p-type semiconductors are neutral. Because in everyone's case, the amount of positive charge in the nucleus is exactly the same amount of electrons outside it. N or P type only dictates which charge will move. That is, in the case of N-type, electrons will move while in P-type, protons will move. Transistors are made of both n-type and p-type semiconductors. A transistor has n-type semiconductors on both sides and p-type semiconductors in the middle. Like a normal switch, there is no electrical connection between the two sides of the transistor. One pass of this transistor is called source and the other pass is called drain. Again, in the case of a simple switch where there is a physical switch, a switch is placed on the p-type semiconductor instead. That is called the gate. And it is isolated from p-type by oxide layer. A special event occurs between p-type and n-type when the complete transistor is made. Since there are more electrons in n-type and holes in p-type on the other hand, all the electrons of n-type come to the holes of p-type and fill them.
Depletion layer
As a result, the border of p-type becomes negative charge. It is called depletion layer. Now if the current flows towards the N-type source, it will be blocked at the depletion layer. And the extra electron in this n-type cannot reach the next n-type. And because of the switch it will indicate off. Again in this situation if a positive charge is applied to the gate above the p-type then the free electron in the as-type will be attracted by the positive charge on the gate i.e. the gate. And if the attraction is strong enough, a part of the depletion layer between n-type and p-type will break. As a result, free electrons can go from the source to the drain. It will then indicate its status.
Conclusion
This is a very nice topic. A hard object indicating on and off without any physical buttons just because of the rise and fall of the voltage. At the same time, the size of these transistors is very small. Even so all transistors cannot be seen without a microscope. Currently, these small transistors such as 5 nanometers (one part of 1 divided by 10000000) are used in various devices. Due to the relatively small size of the transistor, about 750-800 million transistors can be used in a small chip. Which is easily used on a mobile. Reducing this too much will cause a problem and that is the collapse of the depletion layer due to quantum effects. And that transistor will also be damaged or not work. That is, there is a limit to how small the transistor can be. Which is one of the problems in future development. So you have to think of something as an alternative to this transistor. However, it may take another 5-10 years to do this.