TOPIC OF PRESENTATION Gunn Diode GUNN DIODE Definition

TOPIC OF PRESENTATION Gunn Diode

GUNN DIODE Definition • History • Construction •

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.

Symbols for Circuit Diagram:

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 Ga. As semiconductor, in 1963.

Construction: Gunn diodes are fabricated from a single piece of n-type semiconductor, Source Material: Tri-methylgallium and arsenic (10% in H 2). Most Common Materials : Gallium Arsenide (Ga. As) and Indium Phosphide (In. P).

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.

Substrate has doping density n = 1. 3 x 10 ^18 cm-³. Thickness varies according to the frequency required.

Metal contacts consist of three layers, namely a 80 nm layer of Au. Ge sandwiched between two layers of 10 nm of Ni. Additional Au. Ge is evaporated on the existing contacts to a depth of 0. 7μm.

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.

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.

GUNN DIODE Negative Resistance In Gunn Diode

Ga. As (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

(a) How electron move into low mobility ? According to Einstien Equation E=mc 2

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

EFFECT OF NEGATIVE RESISTANCE ON CURRENT

GUNN DIODE Gunn Effect

GUNN DIODE WHICH HAS A RESISTANCE. NEGATIVE DYNAMIC

GRAPH BETWEEN RESISTANCE AND VOLTAGE

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.

CHANGE IN ENERGY R= RL + R(V) WHEN R >0 THE ENERGY OF ANY OSCILLATION TENDS TOBE REDUCEDBY RESISTIVE DISSIPATION.

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

GRAPH BETWEEN RESISTANCE AND CURRENT

WORKING OF GUNN DIODE

COAXIAL CAVITY

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

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

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.

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

GUNN DIODE Difference between Gunn diode and P-N junction

DIFFERENCE BETWEEN GUNN DIODE AND P-N JUNCTION Gunn diode Construction It only consists of N type semiconductor material It has N+ n N+ material No depletion region is formed P-N junction diode It consists of P & N type semiconductor material It has P type, N type and depletion region between these materials

DIFFERENCE BETWEEN GUNN DIODE AND P-N JUNCTION Gunn Doiode P-N junction Diode

DIFFERENCE BETWEEN GUNN DIODE AND P-N JUNCTION Symbols of Gunn Diode P-N junction

DIFFERENCE BETWEEN GUNN DIODE AND P-N JUNCTION Gunn Doiode P-N junction Diode

DIFFERENCE BETWEEN GUNN DIODE AND P-N JUNCTION Gunn Doiode P-N junction Diode

DIFFERENCE BETWEEN GUNN DIODE AND P-N JUNCTION I-V characteristics Of Gunn diode I-V characteristics Of P-N junction Diode

GUNN DIODE Applications

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

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

AUTOMATIC DOOR OPENERS

CAR SPEED DETECTORS

SENSORS TO AVOID DERAILMENT OF TRAINS

MOTION DETECTOR

RADIO AMATEUR USE

GUN OSCILLATOR

Thanks!