1. P-N Junctions Physical aspects of pn junctions Mathematical models Depletion capacitance Breakdown characteristics Basis for other devices Circuit Symbol + V -

2. PHYSICAL ASPECTS OF THE PN JUNCTION

3. P-N Junctions N-type N D P-type N A

4. P-N Junctions N-type N D P-type N A

5. P-N Junctions N-type N D P-type N A Depletion Layer or Region

6. P-N Junctions N-type N D P-type N A Depletion Layer or Region Charge Density qN D -qN A

7. P-N Junctions N-type N D P-type N A Depletion Layer or Region Charge Density qN D -qN A Band Diagram

8. Electrostatics in PN Junction Charge Density qN D -qN A x  Q =  x

9. Electrostatics in PN Junction Charge Density qN D -qN A x x Electric Field Gauss' Law in 1 Dimension: Electric Field =  Q /   Q =  x

10. Electrostatics in PN Junction V bi = Built in Voltage Charge Density qN D -qN A x x x Electric Field Electron Potential Gauss' Law in 1 Dimension: Electric Field =  Q /   Q =  x

11. Why is this the Equilibrium Condition? V bi = built-in voltage = kT ln ( ) NANDNAND ni2ni2

12. Why is this the Equilibrium Condition? V bi = built-in voltage = kT ln ( ) NANDNAND ni2ni2 Too much V bi Too little V bi

13. P-N Junctions --- Diodes N-type N D P-type N A First-Principles Model

14. P-N Junctions --- Diodes N-type N D P-type N A First-Principles Model

15. P-N Junctions --- Diodes N-type N D P-type N A First-Principles Model -0.4-0.3-0.2-0.100.10.20.30.4 0 10 20 30 40 50 60 70 80 90 100 Diode voltage (V) Diode current (nA)

16. P-N Junctions --- Diodes N-type N D P-type N A First-Principles Model

17. Applying Voltage to a Diode - V + FPFP FNFN Forward Bias

18. Applying Voltage to a Diode - V ++ V - FPFP FNFN FNFN FPFP Forward Bias Reverse Bias

19. Capacitance in pn Junctions

21. -3-2.5-2-1.5-0.500.5 0 1 1.5 2 2.5 3 3.5 4 4.5 Diode voltage (V) Capacitance (fF) C j0

22. Breakdown Voltage

23. Caused by Avalanche Multiplication Due to reaching a critical electric field