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T OPIC O F P RESENTATION Gunn Diode. G UNN D IODE Definition History Construction.

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Presentation on theme: "T OPIC O F P RESENTATION Gunn Diode. G UNN D IODE Definition History Construction."— Presentation transcript:

1 T OPIC O F P RESENTATION Gunn Diode

2 G UNN D IODE Definition History Construction

3 Definition: Such type of semiconductor device which have only N type doped (semiconductor) material, is called Gunn Diode. Its 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 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 cm -3 to 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 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 G UNN D IODE 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 E FFECT OF N EGATIVE RESISTANCE ON CURRENT

17 G UNN D IODE Gunn Effect

18 G UNN DIODE WHICH HAS A NEGATIVE DYNAMIC RESISTANCE.

19 G RAPH B ETWEEN R ESISTANCE A ND V OLTAGE

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 C HANGE IN E NERGY R= R L + R (V) W HEN R >0 T HE ENERGY OF ANY OSCILLATION TENDS TO BE REDUCED BY RESISTIVE DISSIPATION.

22 W HEN 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 G RAPH B ETWEEN R ESISTANCE A ND C URRENT

24 W ORKING O F G UNN D IODE

25 C OAXIAL 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 F OR 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 G UNN D IODE Difference between Gunn diode and P-N junction

31 D IFFERENCE BETWEEN G UNN DIODE AND P-N JUNCTION 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 Gunn diode P-N junction diode

32 D IFFERENCE BETWEEN G UNN DIODE AND P-N JUNCTION Gunn Doiode P-N junction Diode

33 D IFFERENCE BETWEEN G UNN DIODE AND P-N JUNCTION Symbols of Gunn Diode P-N junction

34 D IFFERENCE BETWEEN G UNN DIODE AND P-N JUNCTION Gunn Doiode P-N junction Diode

35 D IFFERENCE BETWEEN G UNN DIODE AND P-N JUNCTION Gunn Doiode P-N junction Diode

36 D IFFERENCE BETWEEN G UNN DIODE AND P-N JUNCTION I-V characteristics Of Gunn diode I-V characteristics Of P-N junction Diode

37 G UNN D IODE 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 R ADIO AMATEUR USE

45 G UN OSCILLATOR

46 Thanks!


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