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# why switching speed of tunnel diode is more than ordinary pn

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#### nandinichakrab

##### Newbie level 5
switching speed diode

why do we say that the switching speed of tunnel diode is more than pn diodes? is it true that the electrons travel in the tunnel diode with a velocity comparable with the velocity of light?during tunneling why does the electron wave function penetrate the boundary? the probability of the existance of electron is nill within the boundary,then?

tunnel diode switching speeds

Basically it is the matter of the way electron crosses the barrier. If an electron has enough energy to overcome the barrier, there is a likelyhood of it overcoming / crossing the barrier. The concept of tunelling is better explained with alpha particles / alpha decay. Even though the particle does not have enough energy to overcome the barrier, the wave function (under conditions) is finite beyond the barrier, this in other words implies a finite probability (may be small) of finding that particle beyond the barrier. Thus in tunnelling a particle (or an electron for that matter) may cross the barrier even when its energy is less than the height of the barrier.
When current flows throuhg a conductor, an electron entering a conducter at one end results in an electron leving the other end. This time is short and the velocities so calculated are comparable to the velocity of ligh. Actual velocity can also be found using basics. Th question 'why' is a trouble in quantum mechanics as it is based on postulates and Heisenbergs uncertainty principles. In quantum mechanics terms like nill are not there. One speaks in terms of probabilities ( may be too small to be taken as zero or nill or may be to high to be considered as full or One). This is the consequence of uncertainty prinicple. So if the wave function due to reasons, is finite across the boundary, tunelling can occur. Of course, finite means how much also very much matters.
Raoof

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