Published by: BhumiRaj Timalsina
Published date: 30 Jun 2021
An Introduction to Semiconductors, we can say that semiconductors are the substance that has the resistance level between conductors and insulators. It has an electrical conductivity that falls between conductor such as a metallic copper, and an insulator such as glass. Its resistance falls as its temperature rises. Metals are the just opposite of them. The semiconductors have some of the properties of conductors and some of the insulators. That is why it lies between both of them in terms of many factors.
They display a range of useful properties. For example, passing current becomes easier in one direction, showing variable resistance and sensitivity to heat or light. These types of electrical properties of the semiconductor materials can be changed by doping. Or, by the application of electrical fields or light, devices that are made from the semiconductors are used for the amplification like things. Others like this can be switching and energy conversion also. At absolute zero, a semiconductor acts as an insulator.
In solid-state physics, a bandgap also called an energy gap, is an energy range in a solid where no electronic states can exist. We know that the forbidden gap doesn’t exist in the metals. It is not that there is no gap in the semiconductors. But, the gap is very less. When the temperature increases, some of the valence electron is able to cross the small forbidden gap and reaches to the conduction band. It then leaves the hole behind in the place of the electron. The bandgap is smaller in semiconductors but wide in the insulators.
The figure below shows the bandgap in metals, semiconductors, and insulators.
There are two types of semiconductors:
These are those semiconductors whose impurity concentrations are very low. There is no effect on its electrical properties. This is because they are pure ones. That means they are pure semiconductors.
Extrinsic Semiconductors are those semiconductors in which there is an addition of impurities intentionally for making it conductive.
The use of semiconductors in computers is that they are used for making many devices such as computer chips, both for CPU and memory, bipolar transistors, field-effect transistors, Silicon-controlled rectifiers, etc.