1. LTFY.01.007 – Physics and Engineering
Intrinsic and doped semiconductors. P-N junction. Diodes, LED's, transistors and MOSFET transistor. CCD and CMOS technologies.
LTFY – Physics and Engineering

2. Intrinsic and doped semiconductors
Si – a semiconductor material
At 0K (absolute zero) no free carriers are present !

3. Current in semiconductor device
Supply of new electrons from negatiive terminal !

4. Intrinsic and doped semiconductors
N- and P- doped silicon (Si)

5. A semiconductor crystal – n-doped
Dopant ion + + + + + - + + + - - - - + + + + + + + + - - - - - + + + + + - + + + - - + + + + + + + + - - - + + + + + + + + - - - - + + + + + + + + - - - - + + + + + + + + - - - - -
How does a p-doped semiconductor look like ? + + + + + + + +
Added free charge carrier

6. Putting n-doped and p-doped semiconductor together to form a PN junction
Electric field - - + + + - + + - - + - + + - + - - + + + - - - + + + - - - + + - + - - - - + + + + + + - - + + - - + - - + + - + + + - - - + +
Diffusion force

7. PN- junction animation

8. P-N junction

9. Reverse biasing PN junction+ - - - + + + + - + - + + - + - - - - + + - +

10. Forward biasing PN junction- - - + + - - + + - + + + + - - - - - + - + - - - + + - - - + - - + + - - + + - - + + - +
Recombination of holes and electrons possible if diode is „long“

11. LED – Light Emitting Diode- - - + + - - + + - + + + + + - - - - - - + - + - - - + + - - + - - + - - + + - - + - - + + + - - +

12. Photodiode=solar-cell+ - - + + - + + + + - - - - + - + - - - + + - - - + - - + + + + - - + - +

13. What is a transistor?
An electronic switch for controlling the flow of electric current.
Main types: Bipolar (old), field effect (modern MOSFETs) =

14. C B E Bipolar transistor - - - - - - - - - - - - - - + + + + + + + + +

15. C + + >0.7V B - E Bipolar transistor - - - - - - - - - - - - - - -

16. MOSFET
Closed
Open

17. Transistors as electronic switches = digital logic
Transistors as electronic switches = digital logic. AND gate – just an example
INPUT
OUTPUT A B
A AND B 1

18. RGB image sensor

19. CCD – Charge coupled device

20. CMOS sensor
CMOS active pixel