2Definition History Construction Gunn DiodeDefinitionHistoryConstruction
3Such 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.
5History:Gunn diode was invented by a Physicist, JohnBattiscombe 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 GaAssemiconductor, in 1963.
6Construction: 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).
7Three main areas:Top/Upper Area,Middle Area,Bottom Area.Middle area (Active layer) has a doping level between1014 cm-3 to 1016 cm-3 .
8Substrate has dopingdensityn = 1.3x10 ^18 cm-³.Thickness varies according to thefrequency required.
9Metal contacts consist of three layers, namely a 80 nm layer of AuGe sandwiched between twolayers of 10 nm of Ni.Additional AuGe is evaporated on theexisting contacts to a depth of 0.7μm.
10Its relative stability, and high conductivity. Use Of Gold.Its relative stability,and high conductivity.Requirements:The material must be defect free , and it must alsohave a very uniform level of doping.
11Types of Materials Used For Gunn Diodes To Get Different Frequencies:Gallium arsenide for frequencies upto 200 GHz,Gallium nitride can reach up to 3 THz.
13GaAs (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 EquationE=mc2
15(b) High reverse bias(c) Electron domain formation at thejunction
26In this case, each diode induced fluctuation travels up the cavity and reflected from the far end, returning to the diode after a timeL = length of cavityc= speed of light
27The oscillator may therefore oscillate at any frequency such that. n= the “number of half- waves”
28For a better resultn=1The 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.
29Real 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
31Difference between Gunn diode and P-N junction P-N junction diodeConstructionIt only consists of N type semiconductor materialIt has N+ n N+ materialNo depletion region is formedIt consists of P & N type semiconductor materialIt has P type,N type and depletion region between these materials
32Difference between Gunn diode and P-N junction Gunn DoiodeP-N junction Diode
33Difference between Gunn diode and P-N junction Symbols of Gunn DiodeP-N junction
34Difference between Gunn diode and P-N junction Gunn DoiodeP-N junction Diode
35Difference between Gunn diode and P-N junction Gunn DoiodeP-N junction Diode
36Difference between Gunn diode and P-N junction I-V characteristicsOf Gunn diodeI-V characteristicsOf P-N junction Diode