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PN-type materials introduction
- 1. INTRINSIC & EXTRENSIC MATERIALS:P-TYPE AND N-TYPE INTRODUCTION TO ELECTRICAL ENGINEERING 2021UGECE30 2021UGECE29 tarik & uday kiran D O N E B Y
- 3. INTRODUCTION A semiconductor is a substance that has specific electrical properties that enable it to serve as a foundation for computers and other electronic devices It is typically a solid chemical element or compound that conducts electricity under certain conditions but not others.
- 4. Semiconductor in pure form is known as Intrinsic Semiconductor Ex. Pure Germanium, Pure Silicon At room temp. no of electrons equal to no. of holes. INTRINSIC SEMICONDUCTOR
- 5. PROPERTIES It behaves as an insulator at absolute zero. Electrons are excited by thermal energy They are different from pure semiconductors and may consist of some level of impurities. : 1. 2. 3.
- 6. doping is the intentional introduction of impurities into an intrinsic semiconductor for the purpose of modulating its electrical, optical and structural properties. DOPING
- 8. When we add an impurity to pure semiconductor to increase the charge carriers then it becomes an Extrinsic Semiconductor. In extrinsic semiconductor without breaking the covalent bonds we can increase the charge carriers. EXTRENSIC SEMICONDUCTOTRS
- 9. 1 2 DiodesDiodes are installed in electronic devices as they require a designated unidirectional current flow. Extrinsic semiconductors are used in bipolar junction transistors and field-effect transistors. Most extrinsic semiconductors work as switch devices. 3 APPLICATIONS
- 10. N-TYPE SEMICONDUCTOR When we add a pentavalent impurity to pure semiconductor we get n-type semiconductor Ex: Arsenic (As), Phosphorous (Pi), Antimony (Sb), etc Arsenic atom has 5 valence electrons. Fifth electron is superfluous, becomes free electron and enters into conduction band. Therefore pentavalent impurity donates one electron and becomes positive donor ion. Pentavalent impurity known as donor.
- 12. When we add a Trivalent impurity to pure semiconductor we get p-type semiconductor Ex:Indium ,Gallium,Aluminium,Boron ,etc. Gallium atom has 3 valence electrons It makes covalent bonds with adjacent three electrons of silicon atom. There is a deficiency of one covalent bond and creates a hole. Therefore trivalent impurity accepts one electron and becomes negative acceptor ion. Trivalent impurity known as acceptor. P-TYPE SEMICONDUCTOR
- 13. COMPARISION BETWEEN N AND P TYPE SEMICONDUCTORS Trivalent impurities are added. Majority carriers are holes. Minority carriers are electrons. Fermi level is near the valence band. Pentavalent impurities are added. Majority carriers are electrons. Minority carriers are holes. Fermi level is near the conduction band. N TYPE P TYPE
- 14. COMPARISION OF INTRINSIC AND EXTRINSIC SEMICONDUCTORS It is formed by adding trivalent or pentavalent impurity to a pure semiconductor. No. of holes are more in p-type and no. of electrons are more in n-type. Fermi level lies near valence band in p-type and near conduction band in n-type Ratio of majority and minority carriers are equal It is in pure form Holes and electrons are equal. Fermi level lies in between valence and conduction Bands. Ratio of majority and minority carriers is unity INTRINSIC EXTRENSIC