Semiconductors PDF

Semiconductors Semiconductors Semiconductors are materials which have a conductivity between conductors (generally metals) and non-conductors or insulators (such as ceramics). Gallium arsenide, germanium and silicon are some of the most commonly used semiconductors. Silicon is used in electronic ci...

Semiconductors Semiconductors Semiconductors are materials which have a conductivity between conductors (generally metals) and non-conductors or insulators (such as ceramics). Gallium arsenide, germanium and silicon are some of the most commonly used semiconductors. Silicon is used in electronic circuit fabrication, and gallium arsenide is used in solar cells, laser diodes, etc. Properties of Semiconductors  Semiconductors have the resistivity which is less than insulators and more than conductors.  Semiconductors have negative temperature co-efficient. The resistance in semiconductors increases with the decrease in temperature and vice versa.  The Conducting properties of a Semiconductor change, when a suitable metallic impurity is added to it, which is a very important property. Types of Semiconductors Semiconductors can be classified as follows:  Intrinsic Semiconductor  Extrinsic Semiconductor Intrinsic Semiconductors A Semiconductor in its extremely pure form is said to be an intrinsic semiconductor. The properties of this pure semiconductor are as follows  The number of free electrons is equal to the number of holes.  The conduction capability is small at room temperature. In order to increase the conduction capability of intrinsic semiconductor, it is better to add some impurities. This process of adding impurities is called as Doping. Extrinsic Semiconductor An impure semiconductor, which is formed by doping a pure semiconductor is called as an extrinsic semiconductor. There are two types of extrinsic semiconductors depending upon the type of impurity added. They are N-type extrinsic semiconductor and P-Type extrinsic semiconductor. A small amount of pentavalent impurity is added to a pure semiconductor to result in Ntype extrinsic semiconductor. The added impurity has 5 valence electrons. In N-type extrinsic semiconductor, as the conduction takes place through electrons, the electrons are majority carriers and the holes are minority carriers. P-Type Extrinsic Semiconductor A small amount of trivalent impurity is added to a pure semiconductor to result in P-type extrinsic semiconductor. The added impurity has 3 valence electrons. In P-type extrinsic semiconductor, as the conduction takes place through holes, the holes are majority carriers while the electrons are minority carriers. Uses of Semiconductors in Everyday Life  Temperature sensors are made with semiconductor devices.  They are used in 3D printing machines  Used in microchips and self-driving cars  Used in calculators, solar plates, computers and other electronic devices.  Transistors and MOSFET used as a switch in electrical circuits are manufactured using semiconductors. Industrial Uses of Semiconductors The physical and chemical properties of semiconductors make them capable of designing technological wonders like microchips, transistors, LEDs, solar cells, etc. The microprocessor used for controlling the operation of space vehicles, trains, robots, etc., is made up of transistors and other controlling devices, which are manufactured by semiconductor materials. Importance of Semiconductors Here, we have discussed some advantages of semiconductors, which make them highly useful everywhere.  They are highly portable due to their small size  They require less input power  Semiconductor devices are shockproof  They have a longer lifespan  They are noise-free while operating