Electronics_Devices_class_4.pdf
- 1. Dr. Ambedkar Institute of Technology Electronics Devices (19EC31) Class 4 Dr. Ambedkar Institute of Technology Dr. Shilpa K.C Assistant Professor Dept. of Electronics and Communication Engineering Dr.AIT 09/07/2020 1 Prepared by Dr.Shilpa K.C, Dept of ECE
- 2. Dr. Ambedkar Institute of Technology Energy Bandgap (Eg) Energy Bandgap 09/07/2020 Prepared by Dr.Shilpa K.C, Dept of ECE 2 Semiconductor BandGap 1.Energy difference (in electron volts) between the top of the valence band and the bottom of the conduction band. 2. Type of Bandgap • Direct Bandgap Semiconductor. • Indirect Bandgap Semiconductor.
- 3. Dr. Ambedkar Institute of Technology Direct Bandgap Semiconductor InDirect Bandgap Semiconductor 09/07/2020 Prepared by Dr.Shilpa K.C, Dept of ECE 3 Direct and Indirect BandGap Semiconductor
- 4. Dr. Ambedkar Institute of Technology Direct and Indirect BandGap Semiconductor 09/07/2020 Prepared by Dr.Shilpa K.C, Dept of ECE 4 The material for which maximum of valence band and minimum of conduction band donot occur at the same value of k, k is Propogation Constant Ex. Si, Ge The material for which maximum of valence band and minimum of conduction band lie for same value of k , k is Propogation constant Ex.GaAs, GaN
- 5. Dr. Ambedkar Institute of Technology 09/07/2020 Prepared by Dr.Shilpa K.C, Dept of ECE 5 Direct and Indirect BandGap Semiconductor E-k Diagrams
- 6. Dr. Ambedkar Institute of Technology Direct Bandgap Semiconductor 09/07/2020 Prepared by Dr.Shilpa K.C, Dept of ECE 6 Direct and Indirect BandGap Semiconductor 1. Electrons falling from conduction band to an Valence Band gives of lights(photon) This process is called “ Recombination”. 2. Examples GaAs (Gallium Arsenide) GaN (Gallium Nitride). 3. Examples light-emitting diodes (LEDs), and laser diodes
- 7. Dr. Ambedkar Institute of Technology 09/07/2020 Prepared by Dr.Shilpa K.C, Dept of ECE 7 Energy Band Diagram
- 8. Dr. Ambedkar Institute of Technology Insulator 09/07/2020 Prepared by Dr.Shilpa K.C, Dept of ECE 8 Metals, Semiconductors and Insulators 1. In Insulator - the Energy BandGap (Eg ) is wider between Conduction Band and Valence Band. Diamond -- Eg = 5eV 2. If electric field applied, the electrons in Valence Band (VB) cannot reach Conduction Band. Energy Diagram of Insulator
- 9. Dr. Ambedkar Institute of Technology Metals 09/07/2020 Prepared by Dr.Shilpa K.C, Dept of ECE 9 Metals, Semiconductors and Insulators Energy Diagram of Metals 1. In Metals, valence band and conduction band overlap each other. Therefore, there is no forbidden gap in a conductor or partially filled conduction band 2. A small amount of applied external energy provides enough energy for the valence band electrons to move in to conduction band.
- 10. Dr. Ambedkar Institute of Technology Semiconductor 09/07/2020 Prepared by Dr.Shilpa K.C, Dept of ECE 10 Metals, Semiconductors and Insulators Energy Diagram of Semiconductor 1. In Semiconductor - the Energy BandGap (Eg ) is smaller between Conduction Band and Valence Band than in insulators. Si -- Eg = 1.1eV 2. At 0K, Semiconductor behave as an Insulator. 3. At T> 0K, Semiconductor behave as an Metal
- 11. Dr. Ambedkar Institute of Technology Semiconductor 09/07/2020 Prepared by Dr.Shilpa K.C, Dept of ECE 11 Metals, Semiconductors and Insulators Energy Diagram of Semiconductor 1. A small fraction of the electrons is thermally excited into the conduction band. These electrons carry current just as in metals. 2. The smaller the gap the more electrons in conduction band at a given temperature. 3. Resistivity decreases with temperature due to higher concentration of electrons in conduction band
- 12. Dr. Ambedkar Institute of Technology 09/07/2020 Prepared by Dr.Shilpa K.C, Dept of ECE 12 The Energy Band of Metals, Semiconductors and Insulators
- 13. Dr. Ambedkar Institute of Technology 09/07/2020 Prepared by Dr.Shilpa K.C, Dept of ECE 13 Electrons and Holes
- 14. Dr. Ambedkar Institute of Technology 09/07/2020 Prepared by Dr.Shilpa K.C, Dept of ECE 14 The Valence Band in the Semiconductor Valence Band in Semiconductor • The valence band of with all states filled (electrons) . • The electron with wave vector kj is matched with opposite wave vector –kj . • There is no net current in band unless an electron is removed.
- 15. Dr. Ambedkar Institute of Technology 09/07/2020 Prepared by Dr.Shilpa K.C, Dept of ECE 15 The concept of Hole
- 16. Dr. Ambedkar Institute of Technology 09/07/2020 Prepared by Dr.Shilpa K.C, Dept of ECE 16 Mechanism of Hole movement Hole Movement
- 17. Dr. Ambedkar Institute of Technology 09/07/2020 Prepared by Dr.Shilpa K.C, Dept of ECE 17 Movement of Holes in Valence Band Electrons and Hole directions
- 18. Dr. Ambedkar Institute of Technology Thank You Dr. Ambedkar Institute of Technology HAVE A NICE DAY 09/07/2020 18 Prepared by Dr.Shilpa K.C, Dept of ECE