1. Chapter 5. pn Junction Electrostatics
Preliminaries
Quantitative Electrostatic Relationships

2. ※Doping profile : ND - NA
5. pn Junction Electrostatics
pn junction
※Doping profile : ND - NA

3. ◆ Step junction ＆ Linearly graded junction
5. pn Junction Electrostatics
◆ Step junction ＆ Linearly graded junction

4. ◆ Contact Potential (Built-in Potential) : Vo or Vbi
5. pn Junction Electrostatics
◆ Contact Potential (Built-in Potential) : Vo or Vbi

5. 5. pn Junction Electrostatics

6. ◆ Poisson's Equation *charge density – in the case of fully ionized
5. pn Junction Electrostatics
◆ Poisson's Equation
*charge density – in the case of fully ionized

7. 5. pn Junction Electrostatics
Integrating
At equilibrium,
(2)→(1)

8. 5. pn Junction Electrostatics

9. Quantitative Electrostatic Relationships
5. pn Junction Electrostatics
Quantitative Electrostatic Relationships
◆ Assumptions/Definitions

10. ◆ Step Junction with VA = 0
5. pn Junction Electrostatics
◆ Step Junction with VA = 0
E = 0 outside of the depletion region
p- side of depletion region

11. n-side of depletion region
5. pn Junction Electrostatics
n-side of depletion region

12. p- side of depletion region
5. pn Junction Electrostatics
p- side of depletion region
n- side of depletion region

13. from : depletion region, space charge region
5. pn Junction Electrostatics
from
: depletion region, space charge region
: charge neutrality within the depletion region

14. 5. pn Junction Electrostatics
(4), (5) → (3)

15. 5. pn Junction Electrostatics

16. 5. pn Junction Electrostatics

17. 5. pn Junction Electrostatics

18. Total current diffusion + drift V < 0
5. pn Junction Electrostatics
Total current
diffusion + drift
V < 0
I(gen.) due to EHP generation or minority carriers
V = 0
V > 0
where I0 : I(gen.)
- I0 : reverse saturation current
(4) current flows : in the forward direction
no current flows : in the reverse direction

19. ◆ Step Junction with VA≠0
5. pn Junction Electrostatics
◆ Step Junction with VA≠0
  - Applied Voltage bias VA across the transition region(W) of the junction
    - Change electrostatic potential barrier
    - Change the electric field in the transition region
    - Separation of the energy band
    - Change the width of the depletion region

20. 5. pn Junction Electrostatics

21. 5. pn Junction Electrostatics