Semiconductors and it;s use in IOT
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This document discusses semiconductors and their properties. It explains that semiconductors have electrical conductivity between conductors and insulators. There are two types of semiconductors - intrinsic and extrinsic. Intrinsic semiconductors like silicon are very pure, while extrinsic semiconductors have impurities added to increase conductivity, making them either n-type or p-type semiconductors. Semiconductors are necessary for modern electronics as the basic components of transistors and diodes used in devices like computers.
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Semiconductors and it;s use in IOT
- 1. Md. Mohiuddin Murad 2015-2-55-027 PRESENTED BY:
- 2. SEMICONDUCTORS The materials whose electrical conductivity lies between those of conductors and insulators, are known as semiconductors. Semiconductors are crystalline or amorphous solids with distinct electrical characteristics. Their resistance decreases as their temperature increases, which is behavior opposite to that of a metal. Some common semiconductors : Si - Silicon (most common) Ge - Germanium GaAs
- 3. ENERGY BAND DIAGRAM Forbidden energy band is small for semiconductors. Less energy is required for electron to move from valence to conduction band. A vacancy (hole) remains when an electron leaves the valence band. Hole acts as a positive charge carrier.
- 4. There are two types of Semiconductors 1)Intrinsic Semiconductors 2)Extrinsic Semiconductors Intrinsic Semiconductors:Tetravalent Ex:Si,Ge etc Extrinsic Semiconductors: Ex:p-type and n-type TYPES O F SEMICONDUCTORS
- 5. A semiconductor, which is in its extremely pure form, is known as an intrinsic semiconductor. Silicon and germanium are the most widely used intrinsic semiconductors. Both silicon and germanium are tetravalent, i.e. each has four electrons (valence electrons) in their outermost shell. Each atom shares its four valence electrons with its four immediate neighbors, so that each atom is involved in four covalent bonds. When the temperature of an intrinsic semiconductor is increased, beyond room temperature a large number of electron-hole pairs are generated. INTRINSIC SEMICONDUCTOR
- 6. Pure semiconductors have negligible conductivity at room temperature. To increase the conductivity of intrinsic semiconductor, some impurity is added. The resulting semiconductor is called impure or extrinsic semiconductor. EXTRINSIC SEMICONDUCTOR Two types of impurity atoms are added to the semiconductor Atoms containing 5 valance electrons (Pentavalent impurity atoms) e.g. P, As, Sb, Bi Atoms containing 3 valance electrons (Trivalent impurity atoms) e.g. Al, Ga, B, In N-type semiconductor P-type semiconductor
- 7. N-TYPE SEMICONDUCTOR The semiconductors which are obtained by introducing pentavalent impurity atoms are known as N-type semiconductors. Examples are P, Sb, As and Bi. These elements have 5 electrons in their valance shell. Out of which 4 electrons will form covalent bonds with the neighbouring atoms and the 5th electron will be available as a current carrier. The impurity atom is thus known as donor atom. P-TYPE SEMICONDUCTOR The semiconductors which are obtained by introducing trivalent impurity atoms are known as P-type semiconductors. Examples are Ga, In, Al and B. These elements have 3 electrons in their valance shell which will form covalent bonds with the neighbouring atoms. The fourth covalent bond will remain incomplete. A vacancy, which exists in the incomplete covalent bond constitute a hole. The impurity atom is thus known as acceptor atom.
- 8. . Fermi Level The Fermi level (EF) is the maximumenergy, which can be occupied by an electron at absolute zero (0 K).
- 9. INTRINSIC SEMICONDUCTOR ENERGY BAND DIAGRAM Fermi Level (EF) Forbidden Energy Gap The Fermi level (EF) lies at the middle of the forbidden energy gap.
- 10. FERMI ENERGY DIAGRAM FOR N- TYPE SEMICONDUCTORS Donor Level Energy (eV) The Fermi level (EF) shifts upwards towards the bottom of the conduction band. Fermi Level (EF)
- 11. FERMI ENERGY DIAGRAM FOR P-TYPE SEMICONDUCTORS Energy (eV) The Fermi level (EF) shifts downwards towards the top of the valance band. Acceptor Level Fermi Level (EF)
- 13. NECESSITY OF SEMICONDUCTORS Semiconductors are used in the production of transistors and diodes, as the basic components of modern electronic devices. This technology has completely changed the world we live in because it can produce better, faster, cheaper electronic devices. Not all semiconductors are suitable for computers. Computer semiconductors must be made in a particular way. In 2011, semiconductors were used in 2/3 of the electronic devices, such as personal computers, notebooks made of integrated circuits, tablet computers, calculators and other devices. The continuous improvement of semiconductor manufacturing process is the main reason for the decline in the prices of computers and other similar electronic products.