Tunnel diode: its construction and working, Physics

Assignment Help:

A tunnel diode is a highly conductively two terminal P-N junction doped heavily about 1000 layer width is a high conductively two terminal conventional diode. Because of heavy doping depletion layer width is reduced to an externally small value of the order of 10-5mm reverse breakdown voltage is also reduced to a very small value of the order resulting in appearance to the diode to be broken for any reverse voltage, and a negative resistance section is produced in volt ampere CHARACTISTICS of the diode. It is that the reduced depletion layer can form result in carriers “punching through” the junction with the velocity of light even when they do not possess enough energy to overcome the potential barrier. The result is that large forward current is produced at relatively low forward voltage (less than 100mv) such a mechanism of conduction in which charge carriers (possessing very little energy) punch through a barrier directly instead of climbing over it is called tunnelling. That’s why such diodes are known as tunnel diodes. Because of heavy doping the tunnel diode can conduct in reverse as well as in formed direction but it is usually used in forward biased mode.

CONSTRUCTION OF TUNNEL DIODES: Tunnel diodes are usually fabricated from germanium, gallium arsenide or gallium antimonite. Silicon is not used in the construction of the tunnel diodes because the ratio of peak value of forward current to the value of valley current is maximum in the case of gallium arsenide (approximately 15) and comparatively smaller for germanium (roughly 8) but very in case of silicon (about 3). Tunnel diodes are ordinary manufactured by allowing from gallium arsenide. The source materials are highly doped semiconductor crystal with an impurity concentration of the order of 1025 per cubic meter or more. It is noted that the tunnel diode being a low power device, can be easily damaged by heat and static electrically.

WORKING OF THE TUNNEL DIODES: Tunnel diodes exploit a strange quantum phenomenon called resonant tunnelling to provide interesting forward bias charactistics. When a small forward bias voltage is applied across a tunnel diode, it begins to conduct current. As the voltage is raised, the current increases and attains a peak value known as peak current. If the current is increased a little more, the current actually begins to decreases until it reaches a low point called the valley current. If the voltage is increased further yet, the current begins to increase again, the time without decreasing into another “valley”. The region on the graph where the current is decreasing while applied voltage is increasing is known as the region of the negative resistance.

 


Related Discussions:- Tunnel diode: its construction and working

Explain centrifugal force, Feeling centrifugal force Tie a weight to a...

Feeling centrifugal force Tie a weight to a string about a metre in length and then whirl the weight around at arm's length. View the outward pull on the string. This is centri

Lenzs law, Lenz's law (H.F. Lenz; 1835): An induced electric current a...

Lenz's law (H.F. Lenz; 1835): An induced electric current always pass in such direction that it opposes the change generating it.

Earths rotation about its axis, The earth's rotation about its axis changes...

The earth's rotation about its axis changes measurably over time; You don't have to worry about the details; all you need to know is that our days are growing longer by about 2.3 m

Explain the term magnetic declination, Explain the terms (i) magnetic decli...

Explain the terms (i) magnetic declination and (ii) angle of dip at a given place.

Draw a free-body diagram for a goldfish, Draw a free-body diagram for a gol...

Draw a free-body diagram for a goldfish that is motionless in the middle of a fish bowl. Recognize the forces acting on the fish. Show the direction of the net force on the f

The nearly-free electron model, Consider an electron in a simple one-dimens...

Consider an electron in a simple one-dimensional periodic potential. The energy of the electron will vary periodically due to the influence of the periodic potential, and can be de

Michelson interferometer, what are the condition for obtaining straight lin...

what are the condition for obtaining straight line fringes

Explain ohm''s law, OHM's Law: The current passing by a conductor is di...

OHM's Law: The current passing by a conductor is directly proportional to the potential difference applied across it's end given, the temperature and other physical conditions

What is magnetic field?, It is the area or region around the material where...

It is the area or region around the material where magnetic properties can be found is called as “magnetic field”.

anant kumar

1/26/2013 4:37:02 AM

Write your message here..what is tunneling effect?explain working and characteristic of a tunnel diode.

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd