pn junction diode ppt

1. Title Slide
• PN Junction
• Engineering Physics – 1st Semester

2. Introduction
• A PN junction is formed when a P-type and N-
type semiconductor are joined.
• It is the basic building block of diodes.

3. P-type Semiconductor
• Has more holes than electrons.
• Created by adding trivalent impurities like
Boron.

4. N-type Semiconductor
• Has more electrons than holes.
• Created by adding pentavalent impurities like
Phosphorus.

5. Formation of PN Junction
• When P and N regions meet, electrons and
holes diffuse.
• This creates a depletion region with no free
charge carriers.

6. Depletion Region
• Acts as an insulating layer.
• Built-in electric field forms which opposes
further movement of charges.

7. Biasing of PN Junction
• Forward Bias: Allows current.
• Reverse Bias: Blocks current.

8. Forward Bias Working
• Battery reduces depletion width.
• Current flows easily from P to N.

9. Reverse Bias Working
• Depletion width increases.
• Only a very small leakage current flows.

10. Applications
• Used in diodes, rectifiers, LED, solar cells.
• Important in modern electronics.

11. PN Junction Structure (Professional Diagram)
P-type Semiconductor
High Hole Concentration
N-type Semiconductor
High Electron Concentration
Depletion
Region

12. Reverse Bias Diagram (Professional)
Reverse Bias widens the depletion region.
Current becomes almost zero.