Semiconductor

 Semiconductor

Introduction : In our daily life we com across various things which are made up of semiconductors. In the modern age ,the smart watches that we use, television, smart phone, computers, etc is made up of semiconductor device. The discovery of  semiconductor and transistor on 1947 has changed the history of industrial revolution and modern life. The age of telecommunication started. It has made the machinery to a adjustable and portable size. We will learn in detail about semiconductor devices in this topic.

Electrical conduction in solids : The conduction of electron (charge) depends on various factor such as  availability of free electrons, crystalline structure, temperature, nature of defects present in the solid, charge carriers, etc. Based on this factor we can classify material into three category viz. a) conductor b) semiconductor c) Insulator. Let us study all this three category.

Conductors : The material having large number of conduction electron (Free electron) is capable of conducting electric current. The metals are sea of free electron. The free electron is responsible for electric current. Thus metal is a good conductor of electricity.In normal metal there are approximately 10²⁸ electrons in m³ .Eg : Copper , aluminium, iron,etc.

Insulator : The material having very less  number of conduction electron (Free electron) is not capable of conducting electric current. The non - metals mostly have valence electron and not free electron. The free electron is responsible for electric current. Thus non-metal is bad conductor of electricity.In normal non-metal there are approximately 10²³electrons in m³ .Eg : Plastic, Rubber, Glass,etc.

Semiconductor : Semiconductor is a device whose conductivity lie between conductivity of Conductor and Insulator. In certain condition it is possible to use it as a conductor as well as insulator. The conductivity of semiconductor lies between 10⁴ to 10^-6 Sm^-1 .The conductivity vary from  one semiconductor to another semiconductor depending upon atomic bonding and availability of free electrons.

The number of charge carrier can be controlled by varying temperature.The behaviour of semiconductor can be studied by understanding band theory.Silicon, germanium, gallium arsenide, gallium nitride, cadmium sulphide are some of the commonly used semiconductors.

Photo by Christian Wiediger on Unsplash

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Conductivity of different material

Band theory in solids

Energy band for a typical solids

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