1. Topic Of Presentation
Gunn Diode

2. Definition History Construction
Gunn Diode
Definition
History
Construction

3. Such type of semiconductor device which have only N type doped
Definition:
Such type of semiconductor device which have only N type doped
(semiconductor) material, is called “Gunn Diode.”
It’s a unique component.
Gunn Diode is also known as:
Transferred Electron Device (TED).
Microwave Semiconductor Device.

4. Symbols for Circuit Diagram:

5. History:
Gunn diode was invented by a Physicist, John
Battiscombe Gunn, in 1963, in IBM.
Transferred Electron Effect was first published by:
Ridley and Watkins in 1961.
Further work by Hilsum in 1962,
Finally J.B. Gunn, observed it, using GaAs
semiconductor, in 1963.

6. Construction: Gunn diodes are fabricated from a single piece of n-type
semiconductor,
Source Material:
Tri-methylgallium and arsenic (10% in H2).
Most Common Materials :
Gallium Arsenide (GaAs)
and Indium Phosphide (InP).

7. Three main areas:
Top/Upper Area,
Middle Area,
Bottom Area.
Middle area (Active layer) has a doping level between
1014 cm-3 to 1016 cm-3 .

8. Substrate has doping
density
n = 1.3x10 ^18 cm-³.
Thickness varies according to the
frequency required.

9. Metal contacts consist of three layers, namely a
80 nm layer of AuGe sandwiched between two
layers of 10 nm of Ni.
Additional AuGe is evaporated on the
existing contacts to a depth of 0.7μm.

10. Its relative stability, and high conductivity.
Use Of Gold.
Its relative stability,
and high conductivity.
Requirements:
The material must be defect free , and it must also
have a very uniform level of doping.

11. Types of Materials Used For Gunn Diodes
To Get Different Frequencies:
Gallium arsenide for frequencies up
to 200 GHz,
Gallium nitride can reach up to 3 THz.

12. Negative Resistance In Gunn Diode

13. GaAs (Galliam Arsenide ) has a property of negative resistance.
) The negative resistance in Gunn diode is due to (a) electron transfer to a less mobile energy level (b) high reverse bias (c) electron domain formation at the junction

14. (a)
How electron move into low mobility ?
According to Einstien Equation
E=mc2

15. (b) High reverse bias
(c) Electron domain formation at the
junction

16. Effect of Negative resistance on current

17. Gunn Diode
Gunn Effect

18. Gunn diode which has a negative dynamic resistance.

19. Graph Between Resistance And Voltage

20. As a result we arrange that average voltage on the Gunn diode is as illustrated in figure. The diode is said to be biased into the negative resistance region.

21. Change in Energy R= RL + r(V) When r >0 The energy of any oscillation tends to be reduced by resistive dissipation.

22. When r < 0 The oscillation energy tends to be increased.
According to law of conservation of energy
The amount of energy at r > 0 = The amount of energy at r < 0

23. Graph Between Resistance And Current

24. Working Of Gunn Diode

25. Coaxial cavity

26. In this case, each diode induced fluctuation travels up the cavity and reflected from the far end, returning to the diode after a time
L = length of cavity
c= speed of light

27. The oscillator may therefore oscillate at any frequency such that.
n= the “number of half- waves”

28. For a better result
n=1
The system won't oscillate at a lower frequency because the cavity is too short to permit it. It can't oscillate at a higher frequency because the diode is ‘too slow’, hence we ensure a single-valued oscillation frequency.

29. Real Gunn devices have a response time which varies with the applied voltage, hence we can electronically tune the oscillation frequency by slightly adjusting the bias voltage

30. Difference between Gunn diode and P-N junction

31. Difference between Gunn diode and P-N junction
P-N junction diode
Construction
It only consists of N type semiconductor material
It has N+ n N+ material
No depletion region is formed
It consists of P & N type semiconductor material
It has P type,N type and depletion region between these materials

32. Difference between Gunn diode and P-N junction
Gunn Doiode
P-N junction Diode

33. Difference between Gunn diode and P-N junction
Symbols of Gunn Diode
P-N junction

34. Difference between Gunn diode and P-N junction
Gunn Doiode
P-N junction Diode

35. Difference between Gunn diode and P-N junction
Gunn Doiode
P-N junction Diode

36. Difference between Gunn diode and P-N junction
I-V characteristics
Of Gunn diode
I-V characteristics
Of P-N junction Diode

37. Gunn Diode
Applications

38. A Gunn diode can be used to amplify signals because of the apparent "negative resistance". Gunn diodes are commonly used as a source of high frequency and high power signals

39. Sensors and measuring Instruments Anti-lock brakes
Sensors for monitoring the flow of traffic
Pedestrian safety systems
Distance traveled" recorders
Traffic signal controllers
Automatic traffic gates

40. automatic door openers

41. car speed detectors

42. sensors to avoid derailment of trains

43. motion detector

44. Radio amateur use

45. Gun oscillator

46. Thanks!