2. Band gap material classification (1).pptx

About band gap of semiconductor

1. Prerequisite knowledge: Formation of bands (CB and VB) B and Gap and Material Classification Session No.: 2 Course Name: SCOD Course Code: C1UD124B

2. Key concepts of session no. 2 Galgotias University 2

3. Reflect on the responses of post session activity Galgotias University 3

4. https:// www.youtube.com / watch?v =wa4zmEeuLjQ

5. Learning outcomes Students will be able to

6. The energy difference between the valence band and the conduction band is called energy band gap. It determines the electrical and optical properties of semiconductors and insulators. Energy Band Gap

7. Classification of Materials Conductor ( No Band Gap) : It is material having zero energy band gap. Semiconductor (Small Band Gap: ~0.1 eV to ~3 eV) : The material in which conduction and valence band are separated by small energy band gap Insulator (Large Band Gap: > 3 eV) : It is a material for large energy band gap

8. Think-Pair-Share & Submit on Padlet Given materials with band gap at room temperature. Classify these materials as conductor, semiconductor and insulator Material Band Gap (eV) Copper (Cu) Gallium Arsenide (GaAs) 1.43 Indium Phosphide (InP) 1.35 Gold (Au) Aluminium (Al) Iron (Fe) Silicon (Si) 1.12 Germanium (Ge) 0.66 Aluminium Oxide (Al₂O₃) 9 Magnesium Oxide (MgO) 7.8 Teflon (PTFE) 10 Silicon Carbide (SiC) 3.26 Cadmium Telluride (CdTe) 1.45 Tin Oxide (SnO₂) 3.6 Diamond (C) 5.47 Silicon Dioxide (SiO₂) 8.9 Zirconium Dioxide ( ZrO ₂) 5.8

9. Electrical Conductivity Semiconductors are materials that have electrical conductivity between that of a conductor and an insulator. Conductor: 10 6 to 10 8 siemens/m Semiconductor: 10 -4 to10 2 siemens/ m Insulator: 10 -14 to10 -18 siemens/ m   “The measure of the capability of the material to pass the flow of electric current” 𝜌 = 𝜌 [1+ (T 1 -T 2 )𝛼]

10. Effect of Temperature on Conductivity Conductors : Positive temperature coefficient Semiconductors & Insulators : Negative temperature coefficient

11. Conductors (Decrease in conductivity with increasing temperature): As temperature increases, the atoms or ions in the conductor vibrate more, causing collisions with the free electrons. These collisions reduce the mean free path of the electrons, increasing the resistance and decreasing the conductivity. Semiconductors (Increase in conductivity with increasing temperature): As temperature increases, more electrons gain enough energy to cross the energy gap and enter the conduction band. This increase in carrier concentration (both electrons and holes) leads to an increase in conductivity. Insulators (Very low conductivity): The conductivity of insulators may increase slightly with temperature due to thermal excitation, but it remains very low compared to conductors and semiconductors.

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13. 1. The band gap of a material is the energy difference between: a) Valence band and conduction band b) Conduction band and Fermi level c) Core level and conduction band d) None of the above Answer: a) Valence band and conduction band 2. A material with a band gap greater than 3 eV is typically classified as a: a) Metal b) Semiconductor c) Insulator d) Conductor Answer: c) Insulator 3. At absolute zero temperature , the conductivity of intrinsic semiconductors is: a) Maximum b) Zero c) Infinite d) Same as metals Answer: b) Zero 4. Which material has a negative temperature coefficient of resistance? a) Metals b) Semiconductors c) Superconductors d) Insulators Answer: b) Semiconductors

14. ✓ Learning Activity -2 On wooclap :

15. When a pure semiconductor is heated, its resistance……………. Goes down Goes up Remains same None of these Ans: (a) Goes down As the doping to a pure semiconductor increases, the bulk resistance of the semiconductor…………. Decreases Increases Remains same None of these Ans: Decreases

16. What is the condition at which semiconductor becomes insulator? 2. Can you think a process that can change the band gap of a material? Mind Challenging Questions

17. Summary No Band Gap Small Band Gap: ~0.1 eV to ~3 eV Large Band Gap: > 3 eV

18. Learning outcomes Outcome 1: Identify the materials based on energy band gap Outcome 2: Demonstrate the effect of temperature on conductivity

19. Next topic Semiconducting material properties