current conduction in a semiconductor is explained. Drift and diffusion mechnisms were discussed. Mass action law and electrical neutrality is explained

1. ANIL NEERUKONDA INSTITUTE OF TECHNOLOGY &
SCIENCES(A)
Department of Electronics and Communication Engineering
ECE 125 Basic Electronics Engineering
 Academic year : 2022-23
 Class & Section : 1/4 ECE-A
 Name of the Faculty : Mr.D.Anil Prasad
ANIL PRASAD DADI/ECE/ANITS

2. UNIT-I(Semiconductor Diodes)
• Fermi level in Intrinsic & Extrinsic semiconductors. Mass-Action law.
Mobility and conductivity, Hall effect, Generation and recombination
of charges, Drift and diffusion current, Band structure of open-circuit
p-n junction, V-I characteristics, transition and diffusion capacitance,
reverse recovery time, Avalanche and zener breakdown, zener
diodes, Light Emitting Diodes.
ANIL PRASAD DADI/ECE/ANITS

3. Contents
• Carrier Transport
– Drift mechanism
– Diffusion mechanism
• Mass Action law
• Electrical Neutrality condition
ANIL PRASAD DADI/ECE/ANITS

4. Drift mechanism
• The process by which charge carriers move is called transport.
• Carrier Drift: When a charge carrier moves due to electric field, E
then it is said to be drifting.
ANIL PRASAD DADI/ECE/ANITS
• An electric field applied to a
semiconductor will produce a
force on electron and hole so
that they will experience a net
acceleration and net movement
provided there are available
energy states in the CB and VB.

5. Drift mechanism
• This net movement of charge due to an electric field is called drift.
The net drift of charge gives rise to a drift current.
ANIL PRASAD DADI/ECE/ANITS
• Electric field is constant through
out the material. Voltage, V
along the entire semiconductor
is going to reduce slowly i.e
V,V/2, 3V/2 ….0.

6. Drift mechanism
ANIL PRASAD DADI/ECE/ANITS

7. Drift mechanism
ANIL PRASAD DADI/ECE/ANITS

8. Diffusion mechanism
ANIL PRASAD DADI/ECE/ANITS
0 1 2 x
P p1
p2

9. Diffusion mechanism
ANIL PRASAD DADI/ECE/ANITS
0 1 2 x
P p1
p2

10. Diffusion mechanism
ANIL PRASAD DADI/ECE/ANITS
0 1 2 x
n n1
n2

11. Diffusion mechanism
ANIL PRASAD DADI/ECE/ANITS
0 1 2 x
n n1
n2

12. The Einstein Relationship
ANIL PRASAD DADI/ECE/ANITS

13. Mass Action law
ANIL PRASAD DADI/ECE/ANITS

14. Mass Action law
ANIL PRASAD DADI/ECE/ANITS

15. Mass Action law
ANIL PRASAD DADI/ECE/ANITS
• Mass action law is not valid for degenerate semiconductors but valid
for non degenerate semiconductors

16. Electrical Neutrality condition
• It gives exact relationship among electron, hole, donar and acceptor
atom concentration if material is to remain electrically neutral.
ND+p=NA+n
ANIL PRASAD DADI/ECE/ANITS

17. Electrical Neutrality condition
ANIL PRASAD DADI/ECE/ANITS

18. Electrical Neutrality condition
ANIL PRASAD DADI/ECE/ANITS

19. Electrical Neutrality condition
ANIL PRASAD DADI/ECE/ANITS

20. Electrical Neutrality condition
ANIL PRASAD DADI/ECE/ANITS

21. References
ANIL PRASAD DADI/ECE/ANITS
• Robert L Boylestad, Electronic Devices And Circuit Theory, Prentice
Hall, seventh edition,2021
• Jacob Millman and Christos Halkias, Electronics Devices and
Circuits, Black edition, October,2017

22. Thank you
for listening
ANIL PRASAD DADI/ECE/ANITS