Tunnel diode: its construction and working, Physics

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.

 

Posted Date: 7/9/2012 2:16:37 AM | Location : United States





Write your message here..what is tunneling effect?explain working and characteristic of a tunnel diode.
Posted by anant kumar | Posted Date: 1/26/2013 4:37:02 AM


Related Discussions:- Tunnel diode: its construction and working, Assignment Help, Ask Question on Tunnel diode: its construction and working, Get Answer, Expert's Help, Tunnel diode: its construction and working Discussions

Write discussion on Tunnel diode: its construction and working
Your posts are moderated
Related Questions
Inertia with a spade Scoop up a spadeful of dry earth. Now pitch the earth away from you. View that when the spade stops the earth flies on due to inertia.

Illustrate the polarity of Barrier potential. The  free  electrons  which  cross  over  the  junction  recombine  with  the holes of p-type and uncover some of the negative ac

Demerits of Semiconductor Diode over Vacuum Diode (i)  It can't withstand high reverse voltage (ii)  It can't operate at fairly high temperatures.

An organ pipe which is open at both ends resonates at its fundamental frequency.  Neglecting any end effects, what wavelength is formed by this pipe in this mode of vibration i

Find the resultant of two vectors defined as A=6km east B=8km north

Imagine a small observer is positioned in front of the cork in your picture above. As the cork approaches, the observer measures the wavelength of the waves passing by. How does th

450J of energy are changed into heat in 1 minute. What power is dissipated? A current of 10A ?ows by a conductor and 10Wis dissipated. What p.d. exists across the ends of

Electric Potential: Electric Potential verifies the flow of charge. Its unit is volt, represented as "v".

in water equivalent how the temperature or water and solid equal?

Determine the mass number of the element? A mass of 25.2 g of an element is known to contain 6.77x 10 23 atoms. What is the mass number of the element? I thought it would be